{"gene":"PF3D7_1412600","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2007,"finding":"Truncated DHS from P. falciparum strain NF54 (PF3D7_1412600), expressed as a His-fusion protein and purified by Ni-affinity chromatography, was shown to be a bifunctional enzyme with both deoxyhypusine synthase activity (modifying eIF-5A from P. vivax) and homospermidine synthase activity (0.047 pkatal/mg protein). The DHS inhibitor GC7 inhibited the enzyme with a Ki of 0.1 µM, 2000-fold lower than the non-guanylated derivative 1,7-diaminoheptane.","method":"In vitro enzymatic assay with purified recombinant protein; Ni-affinity chromatography; inhibitor kinetics","journal":"Bioorganic & medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic reconstitution with purified protein and inhibitor kinetics, single lab, single study","pmids":["17591443"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"NF54"}]},{"year":2009,"finding":"DHS from P. falciparum (PF3D7_1412600) was shown by enzymatic studies to catalyze the transfer of an aminobutyl moiety from spermidine to eIF-5A, modifying it to deoxyhypusine-containing eIF-5A; this was confirmed as a discrete first step in the two-enzyme hypusine biosynthesis pathway, with deoxyhypusine hydroxylase (DOHH) completing the modification.","method":"Enzymatic studies (in vitro); structured digital abstract citing MI:0414/MI:0415","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic activity established in two independent studies with purified proteins","pmids":["19740108","17591443"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"Purified P. falciparum DHS (PF3D7_1412600) was inhibited by CNI-1493 with approximately 3-fold inhibition at 2 µM in a direct enzymatic assay; in vitro treatment of P. falciparum-infected erythrocytes with 200 µM CNI-1493 caused parasite clearance within 2 days, attributed to DHS inhibition.","method":"Enzymatic inhibition assay with purified DHS protein; in vitro parasite culture inhibition assay","journal":"Parasitology research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct enzymatic inhibition assay plus cellular growth assay, single lab","pmids":["18256853"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"PfDHS (PF3D7_1412600) was localized to the cytoplasm of asexual-stage P. falciparum parasites by confocal microscopy. Conditional knockdown via glmS riboswitch reduced PfDHS protein ~5-fold, leading to a significant reduction in hypusinated eIF-5A without affecting global protein synthesis, and caused a significant parasite growth defect. Attenuated parasites showed increased sensitivity to GC7 (N1-guanyl-1,7-diaminoheptane). These results establish PfDHS as essential for parasite proliferation and validate it as a druggable antimalarial target.","method":"glmS riboswitch conditional knockdown; confocal microscopy; Western immunoblot; hypusination assay; nascent protein synthesis assay; competitive growth assay; chemogenomic profiling","journal":"PeerJ","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (conditional knockdown, localization, biochemical hypusination assay, chemogenomics) in a single rigorous study with appropriate controls","pmids":["31024761"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2012,"finding":"In vitro knockdown of DHS (PF3D7_1412600) in 293T cells using plasmodial DHS-specific shRNA reduced dhs mRNA and DHS protein levels. In vivo, P. berghei ANKA schizonts transgenic for DHS-specific shRNA showed reduced parasitemia 2–9 days post-infection, absent DHS protein on Western blot, and reduced hypusinated eIF-5A, confirming that DHS is required for parasite proliferation during blood-stage infection. DHS knockdown was also linked to reduced iNOS induction in the host.","method":"RNAi/shRNA knockdown in mammalian cells and transgenic P. berghei; RT-PCR; Western blot; in vivo mouse infection model","journal":"BMC microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo knockdown with multiple readouts (RT-PCR, Western blot, parasitemia), single lab, two experimental systems","pmids":["22694849"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":"ANKA"}]},{"year":2016,"finding":"Attempted full gene disruption of dhs (PF3D7_1412600 ortholog) in P. berghei was unsuccessful; only parasites retaining an episomal copy of the dhs gene were recovered. A knock-in strategy yielded viable recombinant parasites, suggesting that DHS performs an essential function during asexual blood-stage development.","method":"Targeted gene disruption (knock-out attempt) and knock-in in P. berghei; genetic selection","journal":"FEBS open bio","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic essentiality inferred from failed disruption and episome retention, single lab","pmids":["27516964"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2022,"finding":"In dose-dependent enzymatic assays with purified recombinant P. falciparum DHS protein (PF3D7_1412600), the allosteric human DHS inhibitor 6-bromo-N-(1H-indol-4yl)-1-benzothiophene-2-carboxamide achieved only 45% inhibition at 0.4 µM, and chemogenomic profiling with transgenic P. falciparum lines showed that the weak in vitro antiplasmodial activity could not be attributed to Pfdhs targeting. Homology modeling indicated significant structural differences in the allosteric site between human DHS and PfDHS.","method":"In vitro enzymatic inhibition assay with purified recombinant PfDHS; chemogenomic profiling with transgenic parasites; homology modeling","journal":"Molecules (Basel, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 1–2 / Weak — direct enzymatic assay plus chemogenomic profiling, single lab; finding is a negative result about allosteric inhibitor selectivity","pmids":["35458660"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"},{"species":"Plasmodium falciparum","strain":"Dd2"}]},{"year":2004,"finding":"The P. falciparum eIF-5A precursor protein (the substrate of DHS/PF3D7_1412600) was shown to serve as a substrate for human deoxyhypusine synthase in radioactive incorporation studies with [1,8-³H]-spermidine, confirming that PF3D7_1412600's substrate in P. falciparum is the eIF-5A precursor.","method":"Radioactive spermidine incorporation assay (in vitro); recombinant protein expression","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro radiolabeling assay confirming substrate identity, single lab, single method","pmids":["15279952"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PfDHS (PF3D7_1412600) is a cytoplasmic, bifunctional enzyme that catalyzes the first committed step in hypusine biosynthesis by transferring an aminobutyl moiety from spermidine to a specific lysine residue on the eIF-5A precursor to form deoxyhypusine-eIF-5A; it also possesses homospermidine synthase activity; it is essential for asexual blood-stage proliferation in P. falciparum (and P. berghei), as conditional knockdown reduces hypusinated eIF-5A and causes a significant growth defect without affecting global protein synthesis, and its inhibition by GC7 or CNI-1493 arrests parasite growth in vitro and in vivo."},"narrative":{"mechanistic_narrative":"DHS (PF3D7_1412600) catalyzes the first committed step of hypusine biosynthesis in Plasmodium falciparum, transferring an aminobutyl moiety from spermidine to the eIF-5A precursor to generate deoxyhypusine-eIF-5A, with deoxyhypusine hydroxylase completing the modification [PMID:19740108, PMID:17591443]. Recombinant PfDHS is bifunctional, additionally exhibiting homospermidine synthase activity, and is potently inhibited by GC7 (Ki 0.1 µM) [PMID:17591443]. Its physiological substrate is the P. falciparum eIF-5A precursor [PMID:15279952]. PfDHS is cytoplasmic in asexual-stage parasites, and conditional glmS knockdown reduces hypusinated eIF-5A and impairs proliferation without altering global protein synthesis, establishing it as essential and druggable [PMID:31024761]; genetic disruption of the P. berghei ortholog likewise fails except upon episomal complementation [PMID:27516964], and shRNA knockdown reduces parasitemia in vivo [PMID:22694849]. Beyond hypusine-pathway biochemistry, its localization, and essentiality, no further mechanistic detail (e.g. structure, regulatory partners) has been characterized in the available corpus.","teleology":[{"year":2004,"claim":"Before its enzyme was characterized, the identity of the DHS substrate in P. falciparum was established by showing the P. falciparum eIF-5A precursor can be hypusinated, defining the target of the pathway DHS initiates.","evidence":"Radioactive [1,8-³H]-spermidine incorporation assay with recombinant P. falciparum eIF-5A precursor and human DHS","pmids":["15279952"],"confidence":"Medium","gaps":["Used human DHS rather than PfDHS itself as the modifying enzyme","Did not identify the specific modified lysine on Plasmodium eIF-5A"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"Direct reconstitution with purified recombinant protein established that PF3D7_1412600 is itself a bifunctional deoxyhypusine synthase / homospermidine synthase and defined GC7 as a high-affinity inhibitor, converting an inferred activity into a demonstrated enzyme.","evidence":"In vitro enzymatic assay with Ni-purified truncated His-tagged PfDHS from strain NF54; inhibitor kinetics (GC7 Ki 0.1 µM)","pmids":["17591443"],"confidence":"Medium","gaps":["Truncated construct; full-length behavior untested","Biological role of the homospermidine synthase activity in the parasite unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":"NF54"}]},{"year":2008,"claim":"To test druggability, an alternative inhibitor was assayed, showing CNI-1493 inhibits purified PfDHS and clears parasites in culture, linking enzyme inhibition to an antiplasmodial phenotype.","evidence":"Enzymatic inhibition assay with purified PfDHS plus in vitro infected-erythrocyte growth assay","pmids":["18256853"],"confidence":"Medium","gaps":["Only ~3-fold inhibition at 2 µM in vitro; weak potency","Parasite clearance not proven to be on-target via genetic controls"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Enzymatic studies confirmed DHS acts as a discrete first step in the two-enzyme hypusine pathway upstream of DOHH, ordering the biosynthetic route.","evidence":"In vitro enzymatic studies of aminobutyl transfer from spermidine to eIF-5A","pmids":["19740108","17591443"],"confidence":"Medium","gaps":["Kinetic coupling between DHS and DOHH in vivo not characterized"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"claim":"Knockdown moved DHS from an in vitro enzyme to a proliferation requirement, showing reduced DHS lowers hypusinated eIF-5A and parasitemia in a blood-stage infection model.","evidence":"shRNA knockdown in 293T cells and transgenic P. berghei ANKA; RT-PCR, Western blot, in vivo mouse infection","pmids":["22694849"],"confidence":"Medium","gaps":["shRNA-based Plasmodium knockdown is mechanistically atypical","Host iNOS link not mechanistically dissected"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":"ANKA"}]},{"year":2016,"claim":"Genetic essentiality was reinforced by the failure to disrupt the P. berghei dhs ortholog except with an episomal copy, indicating an indispensable asexual blood-stage function.","evidence":"Targeted gene disruption (failed) and knock-in in P. berghei with genetic selection","pmids":["27516964"],"confidence":"Medium","gaps":["Essentiality inferred from failed knockout rather than conditional depletion","Stage-specific requirement beyond asexual blood stage untested"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2019,"claim":"A rigorous conditional-knockdown study established PfDHS as cytoplasmic, essential, and druggable, and pinpointed hypusinated eIF-5A rather than bulk translation as the affected downstream node.","evidence":"glmS riboswitch knockdown, confocal microscopy, hypusination and nascent-protein-synthesis assays, competitive growth and chemogenomic profiling in P. falciparum 3D7","pmids":["31024761"],"confidence":"High","gaps":["Downstream targets of hypusinated eIF-5A that drive the growth defect not identified","No structural basis for essentiality"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2022,"claim":"Testing an allosteric human DHS inhibitor showed it does not effectively target PfDHS, revealing structural divergence at the allosteric site and constraining inhibitor design strategy.","evidence":"Dose-dependent enzymatic assay with purified PfDHS, chemogenomic profiling with transgenic P. falciparum, homology modeling","pmids":["35458660"],"confidence":"Medium","gaps":["Negative result on one compound class; active-site-directed inhibition not addressed","No experimental structure of the PfDHS allosteric site"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"},{"species":"Plasmodium falciparum","strain":"Dd2"}]},{"year":null,"claim":"The structural basis of PfDHS catalysis, the biological role of its homospermidine synthase activity, and the downstream effectors of hypusinated eIF-5A that mediate essentiality remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of PfDHS","Function of homospermidine synthase activity in the parasite unknown","eIF-5A-dependent effectors driving the growth defect unidentified"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["EIF-5A PRECURSOR (SUBSTRATE)","DEOXYHYPUSINE HYDROXYLASE (DOHH; DOWNSTREAM PATHWAY ENZYME)"],"other_free_text":["Inhibited by GC7 (N1-guanyl-1,7-diaminoheptane) with Ki 0.1 µM [#0]; also inhibited by CNI-1493 [#2].","An allosteric human DHS inhibitor does not effectively target PfDHS, reflecting allosteric-site structural divergence [#6].","Essential for asexual blood-stage proliferation in P. falciparum and P. berghei [#3, #4, #5]; knockdown reduces hypusinated eIF-5A without affecting global protein synthesis [#3]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"11728024","id":"PMC_11728024","title":"Effect of drugs inhibiting spermidine biosynthesis and metabolism on the in vitro development of Plasmodium falciparum.","date":"2001","source":"Parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/11728024","citation_count":34,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["deoxyhypusine synthase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25724650","id":"PMC_25724650","title":"From Protease to Decarboxylase: THE MOLECULAR METAMORPHOSIS OF PHOSPHATIDYLSERINE DECARBOXYLASE.","date":"2015","source":"The Journal of biological 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protein and purified by Ni-affinity chromatography, was shown to be a bifunctional enzyme with both deoxyhypusine synthase activity (modifying eIF-5A from P. vivax) and homospermidine synthase activity (0.047 pkatal/mg protein). The DHS inhibitor GC7 inhibited the enzyme with a Ki of 0.1 µM, 2000-fold lower than the non-guanylated derivative 1,7-diaminoheptane.\",\n      \"method\": \"In vitro enzymatic assay with purified recombinant protein; Ni-affinity chromatography; inhibitor kinetics\",\n      \"journal\": \"Bioorganic & medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic reconstitution with purified protein and inhibitor kinetics, single lab, single study\",\n      \"pmids\": [\"17591443\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"NF54\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DHS from P. falciparum (PF3D7_1412600) was shown by enzymatic studies to catalyze the transfer of an aminobutyl moiety from spermidine to eIF-5A, modifying it to deoxyhypusine-containing eIF-5A; this was confirmed as a discrete first step in the two-enzyme hypusine biosynthesis pathway, with deoxyhypusine hydroxylase (DOHH) completing the modification.\",\n      \"method\": \"Enzymatic studies (in vitro); structured digital abstract citing MI:0414/MI:0415\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic activity established in two independent studies with purified proteins\",\n      \"pmids\": [\"19740108\", \"17591443\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Purified P. falciparum DHS (PF3D7_1412600) was inhibited by CNI-1493 with approximately 3-fold inhibition at 2 µM in a direct enzymatic assay; in vitro treatment of P. falciparum-infected erythrocytes with 200 µM CNI-1493 caused parasite clearance within 2 days, attributed to DHS inhibition.\",\n      \"method\": \"Enzymatic inhibition assay with purified DHS protein; in vitro parasite culture inhibition assay\",\n      \"journal\": \"Parasitology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct enzymatic inhibition assay plus cellular growth assay, single lab\",\n      \"pmids\": [\"18256853\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PfDHS (PF3D7_1412600) was localized to the cytoplasm of asexual-stage P. falciparum parasites by confocal microscopy. Conditional knockdown via glmS riboswitch reduced PfDHS protein ~5-fold, leading to a significant reduction in hypusinated eIF-5A without affecting global protein synthesis, and caused a significant parasite growth defect. Attenuated parasites showed increased sensitivity to GC7 (N1-guanyl-1,7-diaminoheptane). These results establish PfDHS as essential for parasite proliferation and validate it as a druggable antimalarial target.\",\n      \"method\": \"glmS riboswitch conditional knockdown; confocal microscopy; Western immunoblot; hypusination assay; nascent protein synthesis assay; competitive growth assay; chemogenomic profiling\",\n      \"journal\": \"PeerJ\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (conditional knockdown, localization, biochemical hypusination assay, chemogenomics) in a single rigorous study with appropriate controls\",\n      \"pmids\": [\"31024761\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In vitro knockdown of DHS (PF3D7_1412600) in 293T cells using plasmodial DHS-specific shRNA reduced dhs mRNA and DHS protein levels. In vivo, P. berghei ANKA schizonts transgenic for DHS-specific shRNA showed reduced parasitemia 2–9 days post-infection, absent DHS protein on Western blot, and reduced hypusinated eIF-5A, confirming that DHS is required for parasite proliferation during blood-stage infection. DHS knockdown was also linked to reduced iNOS induction in the host.\",\n      \"method\": \"RNAi/shRNA knockdown in mammalian cells and transgenic P. berghei; RT-PCR; Western blot; in vivo mouse infection model\",\n      \"journal\": \"BMC microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo knockdown with multiple readouts (RT-PCR, Western blot, parasitemia), single lab, two experimental systems\",\n      \"pmids\": [\"22694849\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"ANKA\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Attempted full gene disruption of dhs (PF3D7_1412600 ortholog) in P. berghei was unsuccessful; only parasites retaining an episomal copy of the dhs gene were recovered. A knock-in strategy yielded viable recombinant parasites, suggesting that DHS performs an essential function during asexual blood-stage development.\",\n      \"method\": \"Targeted gene disruption (knock-out attempt) and knock-in in P. berghei; genetic selection\",\n      \"journal\": \"FEBS open bio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic essentiality inferred from failed disruption and episome retention, single lab\",\n      \"pmids\": [\"27516964\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In dose-dependent enzymatic assays with purified recombinant P. falciparum DHS protein (PF3D7_1412600), the allosteric human DHS inhibitor 6-bromo-N-(1H-indol-4yl)-1-benzothiophene-2-carboxamide achieved only 45% inhibition at 0.4 µM, and chemogenomic profiling with transgenic P. falciparum lines showed that the weak in vitro antiplasmodial activity could not be attributed to Pfdhs targeting. Homology modeling indicated significant structural differences in the allosteric site between human DHS and PfDHS.\",\n      \"method\": \"In vitro enzymatic inhibition assay with purified recombinant PfDHS; chemogenomic profiling with transgenic parasites; homology modeling\",\n      \"journal\": \"Molecules (Basel, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Weak — direct enzymatic assay plus chemogenomic profiling, single lab; finding is a negative result about allosteric inhibitor selectivity\",\n      \"pmids\": [\"35458660\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"},\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"Dd2\"}\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The P. falciparum eIF-5A precursor protein (the substrate of DHS/PF3D7_1412600) was shown to serve as a substrate for human deoxyhypusine synthase in radioactive incorporation studies with [1,8-³H]-spermidine, confirming that PF3D7_1412600's substrate in P. falciparum is the eIF-5A precursor.\",\n      \"method\": \"Radioactive spermidine incorporation assay (in vitro); recombinant protein expression\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro radiolabeling assay confirming substrate identity, single lab, single method\",\n      \"pmids\": [\"15279952\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PfDHS (PF3D7_1412600) is a cytoplasmic, bifunctional enzyme that catalyzes the first committed step in hypusine biosynthesis by transferring an aminobutyl moiety from spermidine to a specific lysine residue on the eIF-5A precursor to form deoxyhypusine-eIF-5A; it also possesses homospermidine synthase activity; it is essential for asexual blood-stage proliferation in P. falciparum (and P. berghei), as conditional knockdown reduces hypusinated eIF-5A and causes a significant growth defect without affecting global protein synthesis, and its inhibition by GC7 or CNI-1493 arrests parasite growth in vitro and in vivo.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DHS (PF3D7_1412600) catalyzes the first committed step of hypusine biosynthesis in Plasmodium falciparum, transferring an aminobutyl moiety from spermidine to the eIF-5A precursor to generate deoxyhypusine-eIF-5A, with deoxyhypusine hydroxylase completing the modification [#1]. Recombinant PfDHS is bifunctional, additionally exhibiting homospermidine synthase activity, and is potently inhibited by GC7 (Ki 0.1 \\u00b5M) [#0]. Its physiological substrate is the P. falciparum eIF-5A precursor [#7]. PfDHS is cytoplasmic in asexual-stage parasites, and conditional glmS knockdown reduces hypusinated eIF-5A and impairs proliferation without altering global protein synthesis, establishing it as essential and druggable [#3]; genetic disruption of the P. berghei ortholog likewise fails except upon episomal complementation [#5], and shRNA knockdown reduces parasitemia in vivo [#4]. Beyond hypusine-pathway biochemistry, its localization, and essentiality, no further mechanistic detail (e.g. structure, regulatory partners) has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Before its enzyme was characterized, the identity of the DHS substrate in P. falciparum was established by showing the P. falciparum eIF-5A precursor can be hypusinated, defining the target of the pathway DHS initiates.\",\n      \"evidence\": \"Radioactive [1,8-\\u00b3H]-spermidine incorporation assay with recombinant P. falciparum eIF-5A precursor and human DHS\",\n      \"pmids\": [\"15279952\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Used human DHS rather than PfDHS itself as the modifying enzyme\", \"Did not identify the specific modified lysine on Plasmodium eIF-5A\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Direct reconstitution with purified recombinant protein established that PF3D7_1412600 is itself a bifunctional deoxyhypusine synthase / homospermidine synthase and defined GC7 as a high-affinity inhibitor, converting an inferred activity into a demonstrated enzyme.\",\n      \"evidence\": \"In vitro enzymatic assay with Ni-purified truncated His-tagged PfDHS from strain NF54; inhibitor kinetics (GC7 Ki 0.1 \\u00b5M)\",\n      \"pmids\": [\"17591443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Truncated construct; full-length behavior untested\", \"Biological role of the homospermidine synthase activity in the parasite unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"NF54\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"To test druggability, an alternative inhibitor was assayed, showing CNI-1493 inhibits purified PfDHS and clears parasites in culture, linking enzyme inhibition to an antiplasmodial phenotype.\",\n      \"evidence\": \"Enzymatic inhibition assay with purified PfDHS plus in vitro infected-erythrocyte growth assay\",\n      \"pmids\": [\"18256853\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only ~3-fold inhibition at 2 \\u00b5M in vitro; weak potency\", \"Parasite clearance not proven to be on-target via genetic controls\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Enzymatic studies confirmed DHS acts as a discrete first step in the two-enzyme hypusine pathway upstream of DOHH, ordering the biosynthetic route.\",\n      \"evidence\": \"In vitro enzymatic studies of aminobutyl transfer from spermidine to eIF-5A\",\n      \"pmids\": [\"19740108\", \"17591443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinetic coupling between DHS and DOHH in vivo not characterized\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Knockdown moved DHS from an in vitro enzyme to a proliferation requirement, showing reduced DHS lowers hypusinated eIF-5A and parasitemia in a blood-stage infection model.\",\n      \"evidence\": \"shRNA knockdown in 293T cells and transgenic P. berghei ANKA; RT-PCR, Western blot, in vivo mouse infection\",\n      \"pmids\": [\"22694849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"shRNA-based Plasmodium knockdown is mechanistically atypical\", \"Host iNOS link not mechanistically dissected\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"ANKA\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Genetic essentiality was reinforced by the failure to disrupt the P. berghei dhs ortholog except with an episomal copy, indicating an indispensable asexual blood-stage function.\",\n      \"evidence\": \"Targeted gene disruption (failed) and knock-in in P. berghei with genetic selection\",\n      \"pmids\": [\"27516964\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Essentiality inferred from failed knockout rather than conditional depletion\", \"Stage-specific requirement beyond asexual blood stage untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A rigorous conditional-knockdown study established PfDHS as cytoplasmic, essential, and druggable, and pinpointed hypusinated eIF-5A rather than bulk translation as the affected downstream node.\",\n      \"evidence\": \"glmS riboswitch knockdown, confocal microscopy, hypusination and nascent-protein-synthesis assays, competitive growth and chemogenomic profiling in P. falciparum 3D7\",\n      \"pmids\": [\"31024761\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream targets of hypusinated eIF-5A that drive the growth defect not identified\", \"No structural basis for essentiality\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Testing an allosteric human DHS inhibitor showed it does not effectively target PfDHS, revealing structural divergence at the allosteric site and constraining inhibitor design strategy.\",\n      \"evidence\": \"Dose-dependent enzymatic assay with purified PfDHS, chemogenomic profiling with transgenic P. falciparum, homology modeling\",\n      \"pmids\": [\"35458660\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative result on one compound class; active-site-directed inhibition not addressed\", \"No experimental structure of the PfDHS allosteric site\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"Dd2\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of PfDHS catalysis, the biological role of its homospermidine synthase activity, and the downstream effectors of hypusinated eIF-5A that mediate essentiality remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of PfDHS\", \"Function of homospermidine synthase activity in the parasite unknown\", \"eIF-5A-dependent effectors driving the growth defect unidentified\"],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0034038\", \"supporting_discovery_ids\": [0, 1, 7]},\n      {\"term_id\": \"GO:0047850\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0008612\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"eIF-5A precursor (substrate)\",\n      \"deoxyhypusine hydroxylase (DOHH; downstream pathway enzyme)\"\n    ],\n    \"other_free_text\": [\n      \"Inhibited by GC7 (N1-guanyl-1,7-diaminoheptane) with Ki 0.1 \\u00b5M [#0]; also inhibited by CNI-1493 [#2].\",\n      \"An allosteric human DHS inhibitor does not effectively target PfDHS, reflecting allosteric-site structural divergence [#6].\",\n      \"Essential for asexual blood-stage proliferation in P. falciparum and P. berghei [#3, #4, #5]; knockdown reduces hypusinated eIF-5A without affecting global protein synthesis [#3].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1412600","name":null,"product":"deoxyhypusine synthase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1030000","name":null,"product":"deoxyhypusine synthase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1345700","name":null,"product":"deoxyhypusine synthase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"DHS","evaluation":null}