{"gene":"PF3D7_1462800","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2000,"finding":"P. falciparum GAPDH (PfGAPDH) was recombinantly expressed in E. coli and shown to exhibit enzymatic (oxidoreductase) activity with NAD+ but not NADP+ as cofactor, establishing cofactor specificity. The gene contains 1 intron and the predicted ORF codes for 337 amino acids (36.6 kDa).","method":"Recombinant protein expression in E. coli, enzymatic activity assay with NAD+ vs NADP+","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay demonstrating cofactor specificity, single lab, single paper","pmids":["10767547"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"finding":"PfGAPDH binds to ferriprotoporphyrin IX (FP/heme) immobilized on agarose (pulldown), and FP inhibits PfGAPDH enzymatic activity with a Ki of 0.2 µM — far more potently than red blood cell GAPDH — suggesting the glycolytic pathway is particularly susceptible to heme-mediated inhibition in the parasite.","method":"Affinity pulldown on FP-agarose; in vitro enzyme inhibition assay with Ki determination","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct binding by affinity pulldown confirmed by enzyme inhibition assay with quantitative Ki, two orthogonal methods in one study","pmids":["12748176"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"finding":"PfGAPDH localizes to both membrane-containing pellet and cytosolic supernatant fractions (whereas aldolase is cytosol-only), and is recruited to membranes in a GTPase Rab2-dependent manner. The N-terminal domain (residues 1–192) of PfGAPDH mediates this Rab2-dependent membrane recruitment, as demonstrated by competitive inhibition with the N-terminal fragment. During schizogony, PfGAPDH accumulates at the parasite periphery and apical region of merozoites, suggesting a non-glycolytic role in vesicular transport and apical organelle biogenesis.","method":"Indirect immunofluorescence; subcellular fractionation; quantitative microsomal binding assay with recombinant fragments; competitive inhibition assay","journal":"Biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal localization by IFA and fractionation, domain mapping by competitive binding assay, two orthogonal approaches in one study","pmids":["12974391"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"Crystal structure of PfGAPDH determined at ~2.25 Å resolution shows a homotetrameric enzyme with one NAD+ per subunit. A unique dipeptide insertion (-KG-) in the S loop, together with characteristic single amino acid substitutions, distinguishes the PfGAPDH active-site groove from human GAPDH and may account for the selective inhibition by ferriprotoporphyrin IX.","method":"X-ray crystallography of recombinant His-tagged protein; structural comparison","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with functional interpretation of unique structural features, validated against known inhibition data","pmids":["16131754"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Crystal structure of PfGAPDH solved at 2.25 Å reveals unexpected extra electron density in the active site (likely the protease inhibitor AEBSF) near the nicotinamide ribose of bound NAD+, identifying a ligand-binding pocket in the active site that can be exploited for inhibitor design.","method":"X-ray crystallography","journal":"Proteins","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — independent crystal structure, single lab, functional interpretation of ligand density is inferred","pmids":["16345073"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"PfGAPDH enzymatic activity is abolished by treatment with 2.5 mM dihydroxyacetone within 6 h in vitro; methylglyoxal at 2.5 mM did not affect PfGAPDH activity over 20 h, distinguishing the two substrates of PfAQP in their ability to inhibit GAPDH.","method":"In vitro enzyme activity assay with recombinant PfGAPDH; compound treatment","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzyme assay, single lab, single paper; negative result for methylglyoxal also recorded","pmids":["16427024"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"PfGAPDH is captured as a substrate/target of cytosolic thioredoxin 1 (PfTrx-1) via a Trx-affinity chromatography approach using a cysteine mutant (C33S) that forms a stable mixed disulfide intermediate. PfTrx-1 was shown to enhance PfGAPDH enzymatic activity, establishing a redox-regulatory interaction.","method":"Trx-affinity chromatography with cysteine mutant PfTrx-1(C33S); LC-MS identification; enzyme activity assay","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — affinity capture with functional validation (activity enhancement), single lab, two orthogonal methods","pmids":["20307687"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"PfGAPDH is a target of S-glutathionylation in P. falciparum, and this modification reversibly inhibits its enzymatic activity. P. falciparum glutaredoxin 1, thioredoxin 1, and plasmoredoxin are each able to catalyze deglutathionylation and thereby restore PfGAPDH activity.","method":"Enzymatic deglutathionylation; affinity purification with biotin-maleimide; proteomics; enzyme activity assay confirming reversible inhibition","journal":"Antioxidants & redox signaling","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — proteomics identification followed by direct enzyme activity assay demonstrating reversible inhibition, multiple deglutathionylating enzymes tested, two orthogonal approaches","pmids":["21595565"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"PfGAPDH binds in a peptide pulldown/SPR assay to the cytoplasmic tails of certain P. falciparum merozoite Reticulocyte Homology (RH) and Duffy Binding-Like (DBL) ligands in a manner dependent on an aromatic amino acid (phenylalanine or tyrosine) in the context of negatively charged residues. This places PfGAPDH as a potential connector between merozoite surface ligands and the actin motor during invasion.","method":"Peptide pulldown binding assay; surface plasmon resonance (SPR)","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — binding confirmed by two orthogonal methods (pulldown + SPR), single lab","pmids":["22991428"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"PfGAPDH is strongly inhibited by S-nitrosylation of its active-site cysteine; this was identified in a systematic biotin-switch/MS screen of the P. falciparum S-nitrosoproteome. Additionally, PfTrx1 was shown to possess transnitrosylating activity at its Cys43 and denitrosylating activity via its active-site cysteines, indicating the thioredoxin system modulates this modification on PfGAPDH.","method":"Biotin-switch assay coupled to mass spectrometry; mechanistic studies of PfTrx1 denitrosylating/transnitrosylating activities","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — proteomics-level identification with mechanistic follow-up on TRX, but direct reversal of PfGAPDH inhibition by TRX not explicitly shown in abstract; single lab","pmids":["24256207"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"3-Bromo-isoxazoline derivatives covalently inhibit PfGAPDH by selectively alkylating the catalytic cysteine, as confirmed by mass spectrometry. Substituents on the isoxazolinic ring modulate potency up to 20-fold, predominantly through an electrostatic effect.","method":"In vitro enzyme inhibition assay; mass spectrometry confirmation of covalent adduct; computational analysis","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — covalent mechanism confirmed by MS, potency modulation explained by computational electrostatics, two orthogonal approaches","pmids":["25137375"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"Recombinant PfGAPDH is a homotetramer with optimal pH ~9; kinetic measurements gave KmNAD = 0.28 mM and KmG3P = 0.25 mM. P. yoelii GAPDH was detected in all four subcellular fractions (cytosol, nucleus, cytoskeleton, membranes) by differential detergent fractionation, with multiple molecular species suggesting post-translational modifications.","method":"Recombinant protein expression and purification; enzyme kinetics; differential detergent fractionation; 2D gel electrophoresis; Western blot; LC-ESI-MS","journal":"Protein expression and purification","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — in vitro kinetics and subcellular fractionation, multiple methods, single lab; P. yoelii result attributed separately","pmids":["26341815"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium yoelii","strain":""}]},{"year":2016,"finding":"3-Bromo-isoxazoline compounds fully inhibit PfGAPDH by alkylating all four catalytic cysteines of the tetramer, whereas under identical conditions human GAPDH was only 25% inhibited with alkylation of a single cysteine. Partial alkylation of human GAPDH produces a conformational rearrangement that restricts access of bulky 3-Br-isoxazoline inhibitors to the remaining active sites, explaining the selectivity.","method":"In vitro enzyme inhibition assay; mass spectrometry of alkylation; structural/conformational analysis","journal":"Bioorganic & medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — covalent mechanism quantified across all four subunits by MS, conformational basis of selectivity identified, two methods, single lab","pmids":["27137361"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"PfGAPDH is present on the surface of Plasmodium sporozoites and directly interacts with CD68 on the Kupffer cell surface, mediating sporozoite traversal of Kupffer cells and subsequent hepatocyte infection. A P39 mimotope peptide identified by phage display was shown to be a structural mimic of PfGAPDH, and an anti-P39 antibody inhibits sporozoite liver invasion without cross-reacting with mammalian GAPDH.","method":"Phage display library screening; direct binding assay (PfGAPDH–CD68 interaction); antibody inhibition assay of liver invasion","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct binding of PfGAPDH to CD68 demonstrated, functional consequence (liver invasion inhibition) shown with specific antibody, multiple orthogonal approaches","pmids":["27551151"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"2-Phenoxy-1,4-naphthoquinone forms a covalent adduct with the PfGAPDH catalytic cysteine through a phenolate displacement mechanism, demonstrated by chemical/biochemical studies. Up to fivefold differences in inactivation rates among GAPDH homologs indicate structural/electrostatic differences in the active sites.","method":"In vitro covalent inhibition assay; analog design; biochemical characterization of adduct formation","journal":"Chemical biology & drug design","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — covalent mechanism defined biochemically, single lab, mechanism inferred partly from analogs","pmids":["28079302"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"The C-terminal end of Plasmodium GAPDH interacts with the Kupffer cell CD68 receptor, and two epitopes within this C-terminal region were identified as the ligand-binding interface required for sporozoite traversal of Kupffer cells.","method":"Epitope mapping; antibody inhibition assay of Plasmodium infection","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — epitope-level mapping of functional interaction domain, single lab, functional inhibition shown","pmids":["30456380"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"PfGAPDH is implicated as a side-product-generating enzyme: its activity produces 4-phosphoerythronate (4-PE) as a damaged metabolite by-product. Accumulation of 4-PE (caused by loss of phosphoglycolate phosphatase PGP) inhibits 6-phosphogluconate dehydrogenase, causing metabolic dysregulation including partial inhibition of upper glycolysis — placing PfGAPDH in a metabolite damage pathway.","method":"Genetic disruption of pgp (KO); metabolite profiling; epistasis/metabolic pathway analysis","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with metabolic profiling and pathway epistasis, but PfGAPDH's role is inferred as the source of 4-PE rather than directly demonstrated","pmids":["31822583"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Two independent genetic screens in P. falciparum converged on resistance alleles in GAPDH that confer fosmidomycin (FSM) resistance. FSM-resistant GAPDH variant proteins are catalytically active but show reduced assembly into the homotetrameric state, altered enzymatic cooperativity, and reduced susceptibility to inhibition by free heme. These data establish that GAPDH oligomerization state controls MEP pathway sensitivity and antimalarial susceptibility.","method":"Parallel genetic resistance screens; metabolic profiling; biochemical characterization of oligomerization; enzyme cooperativity and heme inhibition assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — two parallel screens converged independently, biochemical mechanism (oligomerization, cooperativity, heme sensitivity) directly characterized by multiple orthogonal methods","pmids":["36103572"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum GAPDH (PF3D7_1462800) is a homotetrameric NAD+-dependent glycolytic oxidoreductase whose activity is reversibly inhibited by S-glutathionylation (reversed by glutaredoxin 1, thioredoxin 1, and plasmoredoxin), S-nitrosylation of the active-site cysteine, and covalent alkylation of the catalytic cysteine by small molecules; it is also potently inhibited by free heme (Ki ~0.2 µM) through a structural mechanism linked to a unique S-loop dipeptide insertion; beyond glycolysis, it localizes to the sporozoite surface where its C-terminal domain directly engages Kupffer-cell CD68 to mediate liver invasion, is recruited to parasite membranes via an N-terminal Rab2-dependent mechanism during schizogony, binds cytoplasmic tails of RH/DBL merozoite invasion ligands, and its oligomerization state controls MEP pathway flux and fosmidomycin sensitivity."},"narrative":{"mechanistic_narrative":"PF3D7_1462800 (GAPDH) is the P. falciparum glyceraldehyde-3-phosphate dehydrogenase, an NAD+-specific (not NADP+-dependent) homotetrameric glycolytic oxidoreductase whose catalytic cysteine and quaternary assembly are central to both its metabolic and moonlighting functions [PMID:10767547, PMID:16131754, PMID:26341815]. Its active-site groove carries a unique -KG- dipeptide insertion in the S loop that distinguishes it structurally from human GAPDH and underlies its exceptional sensitivity to inhibition by free heme (ferriprotoporphyrin IX, Ki ~0.2 µM) [PMID:12748176, PMID:16131754]. The enzyme's catalytic cysteine is a hub for reversible redox regulation: S-glutathionylation and S-nitrosylation each inhibit activity, with glutaredoxin 1, thioredoxin 1, and plasmoredoxin reversing glutathionylation and the thioredoxin system modulating nitrosylation [PMID:21595565, PMID:24256207, PMID:20307687]. This same reactive cysteine is exploited by covalent antimalarial chemotypes — 3-bromo-isoxazolines and phenoxynaphthoquinones alkylate it, with selectivity over human GAPDH arising because all four parasite subunits are alkylated whereas partial alkylation of human GAPDH triggers a protective conformational rearrangement [PMID:25137375, PMID:27137361, PMID:28079302]. Beyond glycolysis, GAPDH is recruited to parasite membranes during schizogony via an N-terminal, Rab2-dependent mechanism and accumulates at the merozoite apical region, binds cytoplasmic tails of RH and DBL invasion ligands, and localizes to the sporozoite surface where its C-terminal domain engages Kupffer-cell CD68 to mediate liver-stage traversal and hepatocyte infection [PMID:12974391, PMID:22991428, PMID:27551151, PMID:30456380]. Its oligomerization state also governs antimalarial susceptibility: fosmidomycin-resistance alleles reduce tetramer assembly, alter cooperativity, and blunt heme inhibition, linking GAPDH quaternary structure to MEP pathway flux [PMID:36103572].","teleology":[{"year":2000,"claim":"Establishing that the parasite enzyme is a bona fide NAD+-dependent oxidoreductase defined its basic catalytic identity and cofactor specificity.","evidence":"Recombinant expression in E. coli with NAD+ versus NADP+ activity assays","pmids":["10767547"],"confidence":"Medium","gaps":["No kinetic constants or quaternary structure defined at this stage","No cellular localization or in vivo role addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"claim":"Discovery that heme binds and potently inhibits the enzyme (Ki ~0.2 µM), far more than red-cell GAPDH, identified glycolysis as a heme-vulnerable node unique to the parasite.","evidence":"FP-agarose affinity pulldown plus in vitro inhibition assay with Ki determination","pmids":["12748176"],"confidence":"High","gaps":["Structural basis of selectivity over host GAPDH not yet resolved","Physiological relevance of heme inhibition in intact parasite not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"claim":"Membrane recruitment via the N-terminal domain in a Rab2-dependent manner during schizogony revealed a non-glycolytic role in vesicular transport and apical organelle biogenesis.","evidence":"IFA, subcellular fractionation, and competitive microsomal binding with recombinant N-terminal fragment","pmids":["12974391"],"confidence":"High","gaps":["Direct Rab2–GAPDH interaction interface not defined","Functional consequence of membrane recruitment not tested by loss-of-function"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"claim":"The crystal structure showed a homotetramer with one NAD+ per subunit and a unique S-loop -KG- insertion, providing the structural rationale for selective heme inhibition.","evidence":"X-ray crystallography at ~2.25 Å with comparison to human GAPDH","pmids":["16131754"],"confidence":"High","gaps":["Direct structural evidence of heme bound in the groove not obtained","Link between S-loop insertion and inhibitor selectivity remained inferred"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"A second structure revealed an exploitable ligand-binding pocket in the active site near NAD+, framing the enzyme as an inhibitor-design target.","evidence":"X-ray crystallography with extra active-site electron density","pmids":["16345073"],"confidence":"Medium","gaps":["Identity of the bound ligand only inferred (likely AEBSF)","No demonstrated antimalarial compound occupying this pocket"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"claim":"Identification of reversible S-glutathionylation reversed by glutaredoxin 1, thioredoxin 1, and plasmoredoxin established redox modification of the catalytic cysteine as a physiological activity switch.","evidence":"Biotin-maleimide affinity purification, proteomics, and enzyme activity assays before/after deglutathionylation","pmids":["21595565"],"confidence":"High","gaps":["In vivo trigger and dynamics of glutathionylation not defined","Fraction of cellular GAPDH modified under physiological stress unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"Capture as a thioredoxin 1 substrate that enhances its activity connected the enzyme to the parasite thiol-redox network.","evidence":"Trx-affinity chromatography with PfTrx-1(C33S) mixed-disulfide trap, LC-MS, and activity assay","pmids":["20307687"],"confidence":"Medium","gaps":["Specific cysteine(s) targeted by Trx-1 not mapped","Single-lab affinity capture without reciprocal validation"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Detection of active-site S-nitrosylation as an inhibitory modification, with Trx1 acting as both trans- and de-nitrosylase, extended redox control to nitric-oxide signaling.","evidence":"Biotin-switch/MS S-nitrosoproteome screen plus mechanistic Trx1 assays","pmids":["24256207"],"confidence":"Medium","gaps":["Direct reversal of GAPDH inhibition by Trx1 not explicitly demonstrated","Physiological nitrosylation stoichiometry unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"claim":"Binding to cytoplasmic tails of RH and DBL invasion ligands via an aromatic/charged motif positioned the enzyme as a possible connector between merozoite surface ligands and the actin motor.","evidence":"Peptide pulldown and surface plasmon resonance","pmids":["22991428"],"confidence":"Medium","gaps":["Interaction not validated in intact merozoites","Functional requirement for invasion not tested genetically"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Surface localization on sporozoites and direct binding to Kupffer-cell CD68 defined a moonlighting adhesin role in liver-stage invasion, with an anti-mimotope antibody blocking invasion without host cross-reactivity.","evidence":"Phage display, PfGAPDH–CD68 binding assay, and antibody inhibition of liver invasion","pmids":["27551151"],"confidence":"High","gaps":["Mechanism of surface trafficking of a cytosolic enzyme unresolved","Downstream signaling in Kupffer cells not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Mapping the CD68-binding interface to two C-terminal epitopes localized the adhesive determinant required for Kupffer-cell traversal.","evidence":"Epitope mapping and antibody inhibition of infection","pmids":["30456380"],"confidence":"Medium","gaps":["Structure of the C-terminal–CD68 complex not determined","Epitope-level mapping from a single lab"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Covalent inhibition by 3-bromo-isoxazolines alkylating the catalytic cysteine, tunable by ring substituents, validated the active-site thiol as a druggable target.","evidence":"In vitro inhibition, MS confirmation of adduct, computational electrostatics","pmids":["25137375"],"confidence":"High","gaps":["Selectivity over human GAPDH not yet explained at this stage","Whole-cell antiparasitic efficacy not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Demonstration that full alkylation of all four parasite subunits (versus a protective conformational block in human GAPDH after single-site alkylation) provided a structural basis for inhibitor selectivity.","evidence":"In vitro inhibition, MS quantification of alkylation across subunits, conformational analysis","pmids":["27137361"],"confidence":"High","gaps":["Structural snapshot of the conformational rearrangement not captured","Selectivity not confirmed against other host homologs"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"A second covalent chemotype (phenoxynaphthoquinone) engaging the catalytic cysteine via phenolate displacement, with rate differences among homologs, reinforced active-site electrostatics as a selectivity handle.","evidence":"In vitro covalent inhibition and biochemical adduct characterization with analogs","pmids":["28079302"],"confidence":"Medium","gaps":["Mechanism partly inferred from analog series","No cellular or in vivo validation"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Assigning GAPDH as the source of the damaged metabolite 4-phosphoerythronate placed it within a metabolite-damage pathway whose product, when unrepaired by PGP, dysregulates upper glycolysis and the pentose phosphate pathway.","evidence":"pgp genetic knockout, metabolite profiling, and pathway epistasis","pmids":["31822583"],"confidence":"Medium","gaps":["GAPDH as the 4-PE source is inferred, not directly demonstrated","Rate of side-product formation in vivo unquantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Convergent genetic screens linking GAPDH oligomerization state to fosmidomycin resistance showed that reduced tetramer assembly, altered cooperativity, and diminished heme inhibition control MEP pathway sensitivity, unifying quaternary structure with drug susceptibility.","evidence":"Parallel resistance screens, metabolic profiling, and biochemical assays of oligomerization, cooperativity, and heme inhibition","pmids":["36103572"],"confidence":"High","gaps":["Mechanistic link between GAPDH oligomer state and MEP flux not fully resolved","Structural basis of assembly-defective variants not determined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How a cytosolic glycolytic enzyme is trafficked to and displayed on the sporozoite surface and merozoite membranes, and how its moonlighting adhesin and redox-regulatory roles are coordinated with glycolytic flux in vivo, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No secretion/surface-trafficking mechanism identified for the cytosolic enzyme","No genetic dissection separating glycolytic from moonlighting functions","In vivo contribution of redox modifications to parasite physiology unquantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Homotetramer (each subunit binds one NAD+)"],"partners":["FERRIPROTOPORPHYRIN IX / FREE HEME (INHIBITOR, KI ~0.2 ΜM)","RAB2 GTPASE (N-TERMINAL-DEPENDENT MEMBRANE RECRUITMENT)","THIOREDOXIN 1 (PFTRX-1; ACTIVITY ENHANCEMENT, DENITROSYLATION/TRANSNITROSYLATION)","GLUTAREDOXIN 1 (DEGLUTATHIONYLATION)","PLASMOREDOXIN (DEGLUTATHIONYLATION)","CYTOPLASMIC TAILS OF RH AND DBL MEROZOITE INVASION LIGANDS","KUPFFER-CELL CD68 RECEPTOR (C-TERMINAL DOMAIN)"],"other_free_text":["NAD+-specific, not NADP+-dependent (KmNAD ~0.28 mM, KmG3P ~0.25 mM, optimal pH ~9)","Unique -KG- dipeptide insertion in the S loop distinguishes active-site groove from human GAPDH","Catalytic cysteine is target of reversible S-glutathionylation and S-nitrosylation, and of covalent alkylation by 3-bromo-isoxazolines and 2-phenoxy-1,4-naphthoquinone","Selective covalent inhibition arises from alkylation of all four parasite subunits versus a protective conformational block in human GAPDH","Enzyme activity abolished by dihydroxyacetone but not methylglyoxal in vitro","Fosmidomycin-resistance alleles reduce tetramer assembly, alter cooperativity, and lower heme sensitivity, linking oligomerization to MEP pathway flux","Implicated as source of the damaged metabolite 4-phosphoerythronate","P. yoelii GAPDH detected across cytosolic, nuclear, cytoskeletal, and membrane fractions"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"21595565","id":"PMC_21595565","title":"Protein S-glutathionylation in malaria parasites.","date":"2011","source":"Antioxidants & redox signaling","url":"https://pubmed.ncbi.nlm.nih.gov/21595565","citation_count":87,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GAPDH","glyceraldehyde-3-phosphate dehydrogenase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11738713","id":"PMC_11738713","title":"Determining liver stage parasite burden by real time quantitative PCR as a method for evaluating pre-erythrocytic malaria vaccine efficacy.","date":"2001","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/11738713","citation_count":61,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GAPDH"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12748176","id":"PMC_12748176","title":"Identification and characterization of heme-interacting proteins in the malaria parasite, Plasmodium falciparum.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12748176","citation_count":58,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["GAPDH","glyceraldehyde-3-phosphate dehydrogenase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12974391","id":"PMC_12974391","title":"The N'-terminal domain of glyceraldehyde-3-phosphate dehydrogenase of the apicomplexan Plasmodium falciparum mediates GTPase Rab2-dependent recruitment to 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The gene contains 1 intron and the predicted ORF codes for 337 amino acids (36.6 kDa).\",\n      \"method\": \"Recombinant protein expression in E. coli, enzymatic activity assay with NAD+ vs NADP+\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay demonstrating cofactor specificity, single lab, single paper\",\n      \"pmids\": [\"10767547\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PfGAPDH binds to ferriprotoporphyrin IX (FP/heme) immobilized on agarose (pulldown), and FP inhibits PfGAPDH enzymatic activity with a Ki of 0.2 µM — far more potently than red blood cell GAPDH — suggesting the glycolytic pathway is particularly susceptible to heme-mediated inhibition in the parasite.\",\n      \"method\": \"Affinity pulldown on FP-agarose; in vitro enzyme inhibition assay with Ki determination\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding by affinity pulldown confirmed by enzyme inhibition assay with quantitative Ki, two orthogonal methods in one study\",\n      \"pmids\": [\"12748176\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PfGAPDH localizes to both membrane-containing pellet and cytosolic supernatant fractions (whereas aldolase is cytosol-only), and is recruited to membranes in a GTPase Rab2-dependent manner. The N-terminal domain (residues 1–192) of PfGAPDH mediates this Rab2-dependent membrane recruitment, as demonstrated by competitive inhibition with the N-terminal fragment. During schizogony, PfGAPDH accumulates at the parasite periphery and apical region of merozoites, suggesting a non-glycolytic role in vesicular transport and apical organelle biogenesis.\",\n      \"method\": \"Indirect immunofluorescence; subcellular fractionation; quantitative microsomal binding assay with recombinant fragments; competitive inhibition assay\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal localization by IFA and fractionation, domain mapping by competitive binding assay, two orthogonal approaches in one study\",\n      \"pmids\": [\"12974391\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Crystal structure of PfGAPDH determined at ~2.25 Å resolution shows a homotetrameric enzyme with one NAD+ per subunit. A unique dipeptide insertion (-KG-) in the S loop, together with characteristic single amino acid substitutions, distinguishes the PfGAPDH active-site groove from human GAPDH and may account for the selective inhibition by ferriprotoporphyrin IX.\",\n      \"method\": \"X-ray crystallography of recombinant His-tagged protein; structural comparison\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with functional interpretation of unique structural features, validated against known inhibition data\",\n      \"pmids\": [\"16131754\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure of PfGAPDH solved at 2.25 Å reveals unexpected extra electron density in the active site (likely the protease inhibitor AEBSF) near the nicotinamide ribose of bound NAD+, identifying a ligand-binding pocket in the active site that can be exploited for inhibitor design.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — independent crystal structure, single lab, functional interpretation of ligand density is inferred\",\n      \"pmids\": [\"16345073\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PfGAPDH enzymatic activity is abolished by treatment with 2.5 mM dihydroxyacetone within 6 h in vitro; methylglyoxal at 2.5 mM did not affect PfGAPDH activity over 20 h, distinguishing the two substrates of PfAQP in their ability to inhibit GAPDH.\",\n      \"method\": \"In vitro enzyme activity assay with recombinant PfGAPDH; compound treatment\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzyme assay, single lab, single paper; negative result for methylglyoxal also recorded\",\n      \"pmids\": [\"16427024\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PfGAPDH is captured as a substrate/target of cytosolic thioredoxin 1 (PfTrx-1) via a Trx-affinity chromatography approach using a cysteine mutant (C33S) that forms a stable mixed disulfide intermediate. PfTrx-1 was shown to enhance PfGAPDH enzymatic activity, establishing a redox-regulatory interaction.\",\n      \"method\": \"Trx-affinity chromatography with cysteine mutant PfTrx-1(C33S); LC-MS identification; enzyme activity assay\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — affinity capture with functional validation (activity enhancement), single lab, two orthogonal methods\",\n      \"pmids\": [\"20307687\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PfGAPDH is a target of S-glutathionylation in P. falciparum, and this modification reversibly inhibits its enzymatic activity. P. falciparum glutaredoxin 1, thioredoxin 1, and plasmoredoxin are each able to catalyze deglutathionylation and thereby restore PfGAPDH activity.\",\n      \"method\": \"Enzymatic deglutathionylation; affinity purification with biotin-maleimide; proteomics; enzyme activity assay confirming reversible inhibition\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — proteomics identification followed by direct enzyme activity assay demonstrating reversible inhibition, multiple deglutathionylating enzymes tested, two orthogonal approaches\",\n      \"pmids\": [\"21595565\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PfGAPDH binds in a peptide pulldown/SPR assay to the cytoplasmic tails of certain P. falciparum merozoite Reticulocyte Homology (RH) and Duffy Binding-Like (DBL) ligands in a manner dependent on an aromatic amino acid (phenylalanine or tyrosine) in the context of negatively charged residues. This places PfGAPDH as a potential connector between merozoite surface ligands and the actin motor during invasion.\",\n      \"method\": \"Peptide pulldown binding assay; surface plasmon resonance (SPR)\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — binding confirmed by two orthogonal methods (pulldown + SPR), single lab\",\n      \"pmids\": [\"22991428\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PfGAPDH is strongly inhibited by S-nitrosylation of its active-site cysteine; this was identified in a systematic biotin-switch/MS screen of the P. falciparum S-nitrosoproteome. Additionally, PfTrx1 was shown to possess transnitrosylating activity at its Cys43 and denitrosylating activity via its active-site cysteines, indicating the thioredoxin system modulates this modification on PfGAPDH.\",\n      \"method\": \"Biotin-switch assay coupled to mass spectrometry; mechanistic studies of PfTrx1 denitrosylating/transnitrosylating activities\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — proteomics-level identification with mechanistic follow-up on TRX, but direct reversal of PfGAPDH inhibition by TRX not explicitly shown in abstract; single lab\",\n      \"pmids\": [\"24256207\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"3-Bromo-isoxazoline derivatives covalently inhibit PfGAPDH by selectively alkylating the catalytic cysteine, as confirmed by mass spectrometry. Substituents on the isoxazolinic ring modulate potency up to 20-fold, predominantly through an electrostatic effect.\",\n      \"method\": \"In vitro enzyme inhibition assay; mass spectrometry confirmation of covalent adduct; computational analysis\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — covalent mechanism confirmed by MS, potency modulation explained by computational electrostatics, two orthogonal approaches\",\n      \"pmids\": [\"25137375\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Recombinant PfGAPDH is a homotetramer with optimal pH ~9; kinetic measurements gave KmNAD = 0.28 mM and KmG3P = 0.25 mM. P. yoelii GAPDH was detected in all four subcellular fractions (cytosol, nucleus, cytoskeleton, membranes) by differential detergent fractionation, with multiple molecular species suggesting post-translational modifications.\",\n      \"method\": \"Recombinant protein expression and purification; enzyme kinetics; differential detergent fractionation; 2D gel electrophoresis; Western blot; LC-ESI-MS\",\n      \"journal\": \"Protein expression and purification\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — in vitro kinetics and subcellular fractionation, multiple methods, single lab; P. yoelii result attributed separately\",\n      \"pmids\": [\"26341815\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"3-Bromo-isoxazoline compounds fully inhibit PfGAPDH by alkylating all four catalytic cysteines of the tetramer, whereas under identical conditions human GAPDH was only 25% inhibited with alkylation of a single cysteine. Partial alkylation of human GAPDH produces a conformational rearrangement that restricts access of bulky 3-Br-isoxazoline inhibitors to the remaining active sites, explaining the selectivity.\",\n      \"method\": \"In vitro enzyme inhibition assay; mass spectrometry of alkylation; structural/conformational analysis\",\n      \"journal\": \"Bioorganic & medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — covalent mechanism quantified across all four subunits by MS, conformational basis of selectivity identified, two methods, single lab\",\n      \"pmids\": [\"27137361\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PfGAPDH is present on the surface of Plasmodium sporozoites and directly interacts with CD68 on the Kupffer cell surface, mediating sporozoite traversal of Kupffer cells and subsequent hepatocyte infection. A P39 mimotope peptide identified by phage display was shown to be a structural mimic of PfGAPDH, and an anti-P39 antibody inhibits sporozoite liver invasion without cross-reacting with mammalian GAPDH.\",\n      \"method\": \"Phage display library screening; direct binding assay (PfGAPDH–CD68 interaction); antibody inhibition assay of liver invasion\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding of PfGAPDH to CD68 demonstrated, functional consequence (liver invasion inhibition) shown with specific antibody, multiple orthogonal approaches\",\n      \"pmids\": [\"27551151\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"2-Phenoxy-1,4-naphthoquinone forms a covalent adduct with the PfGAPDH catalytic cysteine through a phenolate displacement mechanism, demonstrated by chemical/biochemical studies. Up to fivefold differences in inactivation rates among GAPDH homologs indicate structural/electrostatic differences in the active sites.\",\n      \"method\": \"In vitro covalent inhibition assay; analog design; biochemical characterization of adduct formation\",\n      \"journal\": \"Chemical biology & drug design\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — covalent mechanism defined biochemically, single lab, mechanism inferred partly from analogs\",\n      \"pmids\": [\"28079302\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The C-terminal end of Plasmodium GAPDH interacts with the Kupffer cell CD68 receptor, and two epitopes within this C-terminal region were identified as the ligand-binding interface required for sporozoite traversal of Kupffer cells.\",\n      \"method\": \"Epitope mapping; antibody inhibition assay of Plasmodium infection\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — epitope-level mapping of functional interaction domain, single lab, functional inhibition shown\",\n      \"pmids\": [\"30456380\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PfGAPDH is implicated as a side-product-generating enzyme: its activity produces 4-phosphoerythronate (4-PE) as a damaged metabolite by-product. Accumulation of 4-PE (caused by loss of phosphoglycolate phosphatase PGP) inhibits 6-phosphogluconate dehydrogenase, causing metabolic dysregulation including partial inhibition of upper glycolysis — placing PfGAPDH in a metabolite damage pathway.\",\n      \"method\": \"Genetic disruption of pgp (KO); metabolite profiling; epistasis/metabolic pathway analysis\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with metabolic profiling and pathway epistasis, but PfGAPDH's role is inferred as the source of 4-PE rather than directly demonstrated\",\n      \"pmids\": [\"31822583\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Two independent genetic screens in P. falciparum converged on resistance alleles in GAPDH that confer fosmidomycin (FSM) resistance. FSM-resistant GAPDH variant proteins are catalytically active but show reduced assembly into the homotetrameric state, altered enzymatic cooperativity, and reduced susceptibility to inhibition by free heme. These data establish that GAPDH oligomerization state controls MEP pathway sensitivity and antimalarial susceptibility.\",\n      \"method\": \"Parallel genetic resistance screens; metabolic profiling; biochemical characterization of oligomerization; enzyme cooperativity and heme inhibition assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — two parallel screens converged independently, biochemical mechanism (oligomerization, cooperativity, heme sensitivity) directly characterized by multiple orthogonal methods\",\n      \"pmids\": [\"36103572\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum GAPDH (PF3D7_1462800) is a homotetrameric NAD+-dependent glycolytic oxidoreductase whose activity is reversibly inhibited by S-glutathionylation (reversed by glutaredoxin 1, thioredoxin 1, and plasmoredoxin), S-nitrosylation of the active-site cysteine, and covalent alkylation of the catalytic cysteine by small molecules; it is also potently inhibited by free heme (Ki ~0.2 µM) through a structural mechanism linked to a unique S-loop dipeptide insertion; beyond glycolysis, it localizes to the sporozoite surface where its C-terminal domain directly engages Kupffer-cell CD68 to mediate liver invasion, is recruited to parasite membranes via an N-terminal Rab2-dependent mechanism during schizogony, binds cytoplasmic tails of RH/DBL merozoite invasion ligands, and its oligomerization state controls MEP pathway flux and fosmidomycin sensitivity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_1462800 (GAPDH) is the P. falciparum glyceraldehyde-3-phosphate dehydrogenase, an NAD+-specific (not NADP+-dependent) homotetrameric glycolytic oxidoreductase whose catalytic cysteine and quaternary assembly are central to both its metabolic and moonlighting functions [#0, #3, #11]. Its active-site groove carries a unique -KG- dipeptide insertion in the S loop that distinguishes it structurally from human GAPDH and underlies its exceptional sensitivity to inhibition by free heme (ferriprotoporphyrin IX, Ki ~0.2 µM) [#1, #3]. The enzyme's catalytic cysteine is a hub for reversible redox regulation: S-glutathionylation and S-nitrosylation each inhibit activity, with glutaredoxin 1, thioredoxin 1, and plasmoredoxin reversing glutathionylation and the thioredoxin system modulating nitrosylation [#7, #9, #6]. This same reactive cysteine is exploited by covalent antimalarial chemotypes — 3-bromo-isoxazolines and phenoxynaphthoquinones alkylate it, with selectivity over human GAPDH arising because all four parasite subunits are alkylated whereas partial alkylation of human GAPDH triggers a protective conformational rearrangement [#10, #12, #14]. Beyond glycolysis, GAPDH is recruited to parasite membranes during schizogony via an N-terminal, Rab2-dependent mechanism and accumulates at the merozoite apical region, binds cytoplasmic tails of RH and DBL invasion ligands, and localizes to the sporozoite surface where its C-terminal domain engages Kupffer-cell CD68 to mediate liver-stage traversal and hepatocyte infection [#2, #8, #13, #15]. Its oligomerization state also governs antimalarial susceptibility: fosmidomycin-resistance alleles reduce tetramer assembly, alter cooperativity, and blunt heme inhibition, linking GAPDH quaternary structure to MEP pathway flux [#17].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that the parasite enzyme is a bona fide NAD+-dependent oxidoreductase defined its basic catalytic identity and cofactor specificity.\",\n      \"evidence\": \"Recombinant expression in E. coli with NAD+ versus NADP+ activity assays\",\n      \"pmids\": [\"10767547\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No kinetic constants or quaternary structure defined at this stage\", \"No cellular localization or in vivo role addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Discovery that heme binds and potently inhibits the enzyme (Ki ~0.2 µM), far more than red-cell GAPDH, identified glycolysis as a heme-vulnerable node unique to the parasite.\",\n      \"evidence\": \"FP-agarose affinity pulldown plus in vitro inhibition assay with Ki determination\",\n      \"pmids\": [\"12748176\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of selectivity over host GAPDH not yet resolved\", \"Physiological relevance of heme inhibition in intact parasite not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Membrane recruitment via the N-terminal domain in a Rab2-dependent manner during schizogony revealed a non-glycolytic role in vesicular transport and apical organelle biogenesis.\",\n      \"evidence\": \"IFA, subcellular fractionation, and competitive microsomal binding with recombinant N-terminal fragment\",\n      \"pmids\": [\"12974391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct Rab2–GAPDH interaction interface not defined\", \"Functional consequence of membrane recruitment not tested by loss-of-function\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The crystal structure showed a homotetramer with one NAD+ per subunit and a unique S-loop -KG- insertion, providing the structural rationale for selective heme inhibition.\",\n      \"evidence\": \"X-ray crystallography at ~2.25 Å with comparison to human GAPDH\",\n      \"pmids\": [\"16131754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural evidence of heme bound in the groove not obtained\", \"Link between S-loop insertion and inhibitor selectivity remained inferred\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"A second structure revealed an exploitable ligand-binding pocket in the active site near NAD+, framing the enzyme as an inhibitor-design target.\",\n      \"evidence\": \"X-ray crystallography with extra active-site electron density\",\n      \"pmids\": [\"16345073\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the bound ligand only inferred (likely AEBSF)\", \"No demonstrated antimalarial compound occupying this pocket\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of reversible S-glutathionylation reversed by glutaredoxin 1, thioredoxin 1, and plasmoredoxin established redox modification of the catalytic cysteine as a physiological activity switch.\",\n      \"evidence\": \"Biotin-maleimide affinity purification, proteomics, and enzyme activity assays before/after deglutathionylation\",\n      \"pmids\": [\"21595565\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo trigger and dynamics of glutathionylation not defined\", \"Fraction of cellular GAPDH modified under physiological stress unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Capture as a thioredoxin 1 substrate that enhances its activity connected the enzyme to the parasite thiol-redox network.\",\n      \"evidence\": \"Trx-affinity chromatography with PfTrx-1(C33S) mixed-disulfide trap, LC-MS, and activity assay\",\n      \"pmids\": [\"20307687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific cysteine(s) targeted by Trx-1 not mapped\", \"Single-lab affinity capture without reciprocal validation\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Detection of active-site S-nitrosylation as an inhibitory modification, with Trx1 acting as both trans- and de-nitrosylase, extended redox control to nitric-oxide signaling.\",\n      \"evidence\": \"Biotin-switch/MS S-nitrosoproteome screen plus mechanistic Trx1 assays\",\n      \"pmids\": [\"24256207\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct reversal of GAPDH inhibition by Trx1 not explicitly demonstrated\", \"Physiological nitrosylation stoichiometry unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Binding to cytoplasmic tails of RH and DBL invasion ligands via an aromatic/charged motif positioned the enzyme as a possible connector between merozoite surface ligands and the actin motor.\",\n      \"evidence\": \"Peptide pulldown and surface plasmon resonance\",\n      \"pmids\": [\"22991428\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction not validated in intact merozoites\", \"Functional requirement for invasion not tested genetically\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Surface localization on sporozoites and direct binding to Kupffer-cell CD68 defined a moonlighting adhesin role in liver-stage invasion, with an anti-mimotope antibody blocking invasion without host cross-reactivity.\",\n      \"evidence\": \"Phage display, PfGAPDH–CD68 binding assay, and antibody inhibition of liver invasion\",\n      \"pmids\": [\"27551151\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of surface trafficking of a cytosolic enzyme unresolved\", \"Downstream signaling in Kupffer cells not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapping the CD68-binding interface to two C-terminal epitopes localized the adhesive determinant required for Kupffer-cell traversal.\",\n      \"evidence\": \"Epitope mapping and antibody inhibition of infection\",\n      \"pmids\": [\"30456380\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structure of the C-terminal–CD68 complex not determined\", \"Epitope-level mapping from a single lab\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Covalent inhibition by 3-bromo-isoxazolines alkylating the catalytic cysteine, tunable by ring substituents, validated the active-site thiol as a druggable target.\",\n      \"evidence\": \"In vitro inhibition, MS confirmation of adduct, computational electrostatics\",\n      \"pmids\": [\"25137375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Selectivity over human GAPDH not yet explained at this stage\", \"Whole-cell antiparasitic efficacy not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstration that full alkylation of all four parasite subunits (versus a protective conformational block in human GAPDH after single-site alkylation) provided a structural basis for inhibitor selectivity.\",\n      \"evidence\": \"In vitro inhibition, MS quantification of alkylation across subunits, conformational analysis\",\n      \"pmids\": [\"27137361\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural snapshot of the conformational rearrangement not captured\", \"Selectivity not confirmed against other host homologs\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"A second covalent chemotype (phenoxynaphthoquinone) engaging the catalytic cysteine via phenolate displacement, with rate differences among homologs, reinforced active-site electrostatics as a selectivity handle.\",\n      \"evidence\": \"In vitro covalent inhibition and biochemical adduct characterization with analogs\",\n      \"pmids\": [\"28079302\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism partly inferred from analog series\", \"No cellular or in vivo validation\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Assigning GAPDH as the source of the damaged metabolite 4-phosphoerythronate placed it within a metabolite-damage pathway whose product, when unrepaired by PGP, dysregulates upper glycolysis and the pentose phosphate pathway.\",\n      \"evidence\": \"pgp genetic knockout, metabolite profiling, and pathway epistasis\",\n      \"pmids\": [\"31822583\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GAPDH as the 4-PE source is inferred, not directly demonstrated\", \"Rate of side-product formation in vivo unquantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Convergent genetic screens linking GAPDH oligomerization state to fosmidomycin resistance showed that reduced tetramer assembly, altered cooperativity, and diminished heme inhibition control MEP pathway sensitivity, unifying quaternary structure with drug susceptibility.\",\n      \"evidence\": \"Parallel resistance screens, metabolic profiling, and biochemical assays of oligomerization, cooperativity, and heme inhibition\",\n      \"pmids\": [\"36103572\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between GAPDH oligomer state and MEP flux not fully resolved\", \"Structural basis of assembly-defective variants not determined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a cytosolic glycolytic enzyme is trafficked to and displayed on the sporozoite surface and merozoite membranes, and how its moonlighting adhesin and redox-regulatory roles are coordinated with glycolytic flux in vivo, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No secretion/surface-trafficking mechanism identified for the cytosolic enzyme\", \"No genetic dissection separating glycolytic from moonlighting functions\", \"In vivo contribution of redox modifications to parasite physiology unquantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004365\", \"supporting_discovery_ids\": [0, 11]},\n      {\"term_id\": \"GO:0051287\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0020037\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0042803\", \"supporting_discovery_ids\": [3, 11, 17]},\n      {\"term_id\": \"GO:0005102\", \"supporting_discovery_ids\": [8, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 11]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0009986\", \"supporting_discovery_ids\": [13, 15]},\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006096\", \"supporting_discovery_ids\": [0, 16]},\n      {\"term_id\": \"GO:0006094\", \"supporting_discovery_ids\": [16, 17]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [13, 15]},\n      {\"term_id\": \"GO:0006809\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"complexes\": [\n      \"Homotetramer (each subunit binds one NAD+)\"\n    ],\n    \"partners\": [\n      \"Ferriprotoporphyrin IX / free heme (inhibitor, Ki ~0.2 µM)\",\n      \"Rab2 GTPase (N-terminal-dependent membrane recruitment)\",\n      \"Thioredoxin 1 (PfTrx-1; activity enhancement, denitrosylation/transnitrosylation)\",\n      \"Glutaredoxin 1 (deglutathionylation)\",\n      \"Plasmoredoxin (deglutathionylation)\",\n      \"Cytoplasmic tails of RH and DBL merozoite invasion ligands\",\n      \"Kupffer-cell CD68 receptor (C-terminal domain)\"\n    ],\n    \"other_free_text\": [\n      \"NAD+-specific, not NADP+-dependent (KmNAD ~0.28 mM, KmG3P ~0.25 mM, optimal pH ~9)\",\n      \"Unique -KG- dipeptide insertion in the S loop distinguishes active-site groove from human GAPDH\",\n      \"Catalytic cysteine is target of reversible S-glutathionylation and S-nitrosylation, and of covalent alkylation by 3-bromo-isoxazolines and 2-phenoxy-1,4-naphthoquinone\",\n      \"Selective covalent inhibition arises from alkylation of all four parasite subunits versus a protective conformational block in human GAPDH\",\n      \"Enzyme activity abolished by dihydroxyacetone but not methylglyoxal in vitro\",\n      \"Fosmidomycin-resistance alleles reduce tetramer assembly, alter cooperativity, and lower heme sensitivity, linking oligomerization to MEP pathway flux\",\n      \"Implicated as source of the damaged metabolite 4-phosphoerythronate\",\n      \"P. yoelii GAPDH detected across cytosolic, nuclear, cytoskeletal, and membrane fractions\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1462800","name":null,"product":"glyceraldehyde-3-phosphate dehydrogenase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1326400","name":null,"product":"glyceraldehyde-3-phosphate dehydrogenase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1218700","name":null,"product":"glyceraldehyde-3-phosphate dehydrogenase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"GAPDH","evaluation":null}