Affinage · Plasmodium

LipL2

PF3D7_0923600 · lipoate-protein ligase 2

Annotated
2026-09-08
7 papers in source corpus 7 papers cited in narrative 7 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

LipL2 (PF3D7_0923600) is a lipoate-attachment enzyme of P. falciparum that operates in the lipoate-scavenging arm of the parasite's lipoylation machinery, dually targeted to both the mitochondrion and the apicoplast (PMID:17244193, PMID:18069893). Rather than acting as a canonical lipoate ligase, LipL2 functions as a lipoyltransferase: it cannot independently lipoylate any mitochondrial substrate, and instead works together with LipL1 through a redox-gated mechanism in which, under strongly reducing conditions, LipL1 activates lipoate and LipL2 transfers it to the E2 subunits of the branched-chain ketoacid dehydrogenase (BCDH) and α-ketoglutarate dehydrogenase (KDH) (PMID:25116855, PMID:28836704). In the apicoplast, LipL2 provides residual lipoylation of the pyruvate dehydrogenase E2 subunit when the biosynthetic enzyme LipB is disrupted (PMID:18069893). LipL2 is essential for parasite survival solely because this lipoylation-dependent BCDH/KDH activity supplies mitochondrial acetyl-CoA required for histone and other protein acetylation outside the mitochondrion (PMID:37068227).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 2007 Medium

    Establishing whether PF3D7_0923600 is a functional lipoate-handling enzyme at all, its capacity to scavenge lipoate was tested by heterologous rescue.

    Evidence Complementation of lipoylation-deficient bacteria by LipL2, with radiolabel incorporation in parasites

    PMID:17244193

    Open questions at the time
    • Bacterial complementation does not define the native parasite substrates
    • Does not distinguish ligase from transferase activity
  2. 2007 Medium

    To place LipL2 within the parasite's compartmentalized lipoate pathways, its subcellular targeting and functional role were probed genetically.

    Evidence Fluorescence localization plus LipB disruption with immunodetection of lipoylated PDH E2 in P. falciparum

    PMID:18069893

    Open questions at the time
    • Dual targeting mechanism to two organelles not defined
    • Extent of apicoplast vs mitochondrial contribution unquantified
  3. 2012 Low

    Whether LipL2 is functionally redundant with LipL1 was addressed, indicating a distinct, non-compensating role in blood-stage lipoylation.

    Evidence Review summarizing localization and genetic knockdown/functional analysis in P. falciparum

    PMID:22607141

    Open questions at the time
    • Review article with no new primary data
    • Mechanistic basis of the LipL1/LipL2 distinction not established here
  4. 2014 High

    The key mechanistic question — how LipL2 lipoylates its targets — was answered by showing it acts not alone but through a redox-sensitive two-enzyme mechanism with LipL1.

    Evidence In vitro lipoylation assays with defined substrates under manipulated redox conditions in P. falciparum

    PMID:25116855

    Open questions at the time
    • Molecular basis of the redox switch not resolved
    • Physiological redox state driving BCDH/KDH lipoylation in vivo unmeasured
  5. 2017 High

    The enzymatic identity of LipL2 was refined to a lipoyltransferase of a novel clade, with LipL1 acting as the redox switch that partners with LipL2 for BCDH/KDH lipoylation.

    Evidence Biochemical activity characterization, phylogenetic analysis, and redox-state in vitro lipoylation assays in P. falciparum

    PMID:28836704

    Open questions at the time
    • Structural basis of transferase catalysis not determined
    • How lipoate is channeled between LipL1 and LipL2 unresolved
  6. 2017 Medium

    Whether the LipL2 ortholog serves as a compensatory pathway was tested in a rodent model, showing transcriptional upregulation upon loss of the partner enzyme.

    Evidence Anhydrotetracycline-inducible conditional knockout of LplA1 with RT-PCR profiling of lplA2 in P. berghei

    PMID:28655332

    Open questions at the time
    • mRNA upregulation not shown to restore lipoylation functionally
    • Rodent finding not directly extended to P. falciparum LipL2
  7. 2023 High

    Why LipL2 is essential was resolved by tracing its function to acetyl-CoA supply, linking mitochondrial dehydrogenase lipoylation to downstream protein acetylation.

    Evidence Metabolite-labeling and genetic-deletion epistasis measuring dehydrogenase activity and acetylation output in P. falciparum

    PMID:37068227

    Open questions at the time
    • Contribution of the apicoplast-targeted pool to essentiality not separated
    • Mechanism of acetyl-CoA export/use for cytosolic acetylation not detailed

Open questions

Synthesis pass · forward-looking unresolved questions
  • The structural and molecular basis of the LipL1/LipL2 redox-gated lipoate transfer, and the physiological role of LipL2's apicoplast pool, remain open.
  • No structure of LipL2 or the LipL1-LipL2 assembly
  • Redox sensor identity and in vivo trigger unknown
  • Distinct apicoplast function versus mitochondrial function not disentangled

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
LIPL1

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 LipL2 (PF3D7_0923600) restored lipoate scavenging in lipoylation-deficient bacteria, demonstrating that it is a functional lipoate-scavenging enzyme in P. falciparum. Complementation assay in lipoylation-deficient bacteria Molecular microbiology Medium 17244193
2007 LipL2 (PF3D7_0923600) is dually targeted to both the mitochondrion and the apicoplast in P. falciparum erythrocytic stages, and provides residual lipoylation of the apicoplast-located pyruvate dehydrogenase E2 subunit when the biosynthetic enzyme LipB is disrupted, indicating a functional lipoate protein ligase activity in the apicoplast. Localization studies (fluorescence microscopy) and genetic disruption of LipB combined with immunodetection of lipoylated PDH PLoS pathogens Medium 18069893
2012 LipL2 (PF3D7_0923600) is located in both the mitochondrion and the apicoplast, and cannot compensate for the loss of LipL1 function during blood-stage development, suggesting a specific function for LipL2 that is distinct from LipL1's role in lipoylating mitochondrial substrates. Localization studies and genetic knockdown/functional analysis Current pharmaceutical design Low 22607141
2014 LipL2 (PF3D7_0923600) does not show canonical lipoate ligase activity and cannot independently lipoylate any of the mitochondrial substrates (H-protein, BCDH E2, or KDH E2). Instead, BCDH and KDH are lipoylated through a novel redox-sensitive mechanism requiring both LipL1 and LipL2, where strong reducing conditions are required specifically for BCDH and KDH lipoylation. In vitro lipoylation assays, redox-condition manipulation, and biochemical analysis of parasite protein lipoylation Molecular microbiology High 25116855
2017 LipL2 (PF3D7_0923600) functions as a lipoyltransferase (not a canonical ligase) and is a member of a novel clade of lipoate attachment enzymes. PfLipL1 acts as a redox switch: depending on the lipoate redox state, it either functions as a canonical lipoate ligase (lipoylating H-protein) or as a lipoate-activating enzyme that works in conjunction with PfLipL2 to lipoylate BCDH and KDH. Biochemical characterization of enzyme activity, phylogenetic analysis, and in vitro lipoylation assays with redox-state manipulation Molecular microbiology High 28836704
2017 In P. berghei, the ortholog of LipL2 (lplA2) shows significantly increased mRNA expression when LplA1 is conditionally knocked out in late-stage infection, indicating that LipL2 can be activated as an alternative/compensatory pathway to maintain lipoic acid metabolism in the absence of LplA1. Conditional knockdown of LplA1 using anhydrotetracycline-inducible system; RT-PCR/gene expression profiling of lplA2 mRNA Parasites & vectors Medium 28655332
2023 LipL2 (PF3D7_0923600) is essential for parasite survival solely because of its role in supporting mitochondrial acetyl-CoA metabolism: it is required for the lipoylation-dependent activity of the ketoacid dehydrogenase enzymes (BCDH and KDH), whose acetyl-CoA output is in turn required for histone acetylation and protein acetylation outside the mitochondrion. Metabolite-labeling experiments in P. falciparum lines with genetic deletions affecting mitochondrial dehydrogenase activity; epistasis analysis Proceedings of the National Academy of Sciences of the United States of America High 37068227

Source papers

Stage 0 corpus · 7 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 Scavenging of the cofactor lipoate is essential for the survival of the malaria parasite Plasmodium falciparum. Molecular microbiology 66 17244193
2007 Apicoplast lipoic acid protein ligase B is not essential for Plasmodium falciparum. PLoS pathogens 42 18069893
2012 Lipoic acid metabolism of Plasmodium--a suitable drug target. Current pharmaceutical design 31 22607141
2014 Redox-dependent lipoylation of mitochondrial proteins in Plasmodium falciparum. Molecular microbiology 19 25116855
2023 The mitochondrion of Plasmodium falciparum is required for cellular acetyl-CoA metabolism and protein acetylation. Proceedings of the National Academy of Sciences of the United States of America 14 37068227
2017 A novel lipoate attachment enzyme is shared by Plasmodium and Chlamydia species. Molecular microbiology 13 28836704
2017 Conditional knock-out of lipoic acid protein ligase 1 reveals redundancy pathway for lipoic acid metabolism in Plasmodium berghei malaria parasite. Parasites & vectors 4 28655332