GPAM encodes glycerol-3-phosphate acyltransferase 1 (GPAT1), the mitochondrial, N-ethylmaleimide-resistant glycerol-3-phosphate acyltransferase of the GPAT/DHAPAT (PlsB-like) acyltransferase family. GPAT1 transfers a long-chain fatty acyl group, preferentially a saturated palmitoyl group, from acyl-CoA to the sn-1 position of sn-glycerol 3-phosphate, producing 1-acyl lysophosphatidic acid. This is the first step of de novo glycerolipid synthesis; the lysophosphatidic acid is then acylated to phosphatidic acid by other enzymes and routed into diacylglycerol, triacylglycerol and glycerophospholipids. GPAT1 acts on the cytosolic face of the mitochondrial outer membrane, which it binds peripherally through an amphipathic surface patch and an N-terminal loop-helix region carrying the mitochondrial-targeting signal rather than through transmembrane helices. Its catalytic N-terminal acyltransferase domain contains the HXXXXD motif and is stabilised by a tightly associated C-terminal domain. GPAT1 is abundant in liver and adipose tissue, is induced under lipogenic conditions, and in mouse knockouts is needed to channel newly synthesised fatty acids into triacylglycerol, to place palmitate at the sn-1 position of phospholipids, and to divert fatty acids away from mitochondrial beta-oxidation.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | MODIFY | Summary: Correct but less specific than the supported location; GPAT1 acts on the cytosolic face of the mitochondrial outer membrane. Reason: The PAINT IBD at PTN000970957 (the GPAT1 plus GPAT2 clade, taxon Eumetazoa) places 'mitochondrion', and human GPAM sits inside that clade in PANTHER subfamily PTHR12563:SF16, so the inheritance is sound. The term is nevertheless more general than what is known for GPAM itself. The human cryo-EM study and UniProt's curated subcellular location place the protein on the mitochondrial outer membrane, a part_of descendant that GPAM already carries (IEA and four Reactome TAS rows). Refine to GO:0005741. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: PANTHER:PTN000970957 SUPPORTS TRANSFER Eumetazoa GPAT1/GPAT2 node; human GPAM (PTHR12563:SF16) is a descendant. The node-level term is correctly scoped for the clade; the refinement to the outer membrane uses GPAM-specific evidence and is not a propagation failure. Proposed replacements: mitochondrial outer membrane Supporting Evidence: PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. file:human/GPAM/GPAM-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion outer membrane |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Core catalytic activity, inherited at the GPAT1/GPAT2 PAINT node and directly demonstrated for human GPAT1. Reason: The IBD at PTN000970957 is seeded by mouse and rat Gpam (SF16), human GPAT2 (Q6NUI2, SF15) and human GPAM itself. GPAM's presence among the seeds reflects its own experimental annotation, which is expected and not circular. Human GPAT1 activity is shown by the cryo-EM/functional study and the UniProt curated reactions (RHEA:15325 and acyl-chain-specific reactions, ECO:0000269). Supporting Evidence: PMID:36522428 Here we present the cryo-EM structures of human GPAT1 in substrate analog-bound and product-bound states. file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- |
| GO:0006650 glycerophospholipid metabolic process | IBA GO_REF:0000033 | MODIFY | Summary: Correct but general; GPAT1 performs the first, lysophosphatidic-acid-forming step of de novo phosphatidic acid synthesis. Reason: The PAINT node assertion is sound for the GPAT1/GPAT2 clade, but for GPAM the process can be stated more precisely. GPAT1 makes 1-acyl lysophosphatidic acid, the precursor that AGPATs convert to phosphatidic acid, so it carries out a step of phosphatidic acid biosynthetic process (GO:0006654), an is_a descendant of glycerophospholipid metabolic process that GPAM already carries (Reactome TAS, ISS). Propagation Review Root cause: NO FAILURE NON CORE Sources checked: PANTHER:PTN000970957 SUPPORTS TRANSFER Eumetazoa GPAT1/GPAT2 node; human GPAM (PTHR12563:SF16) is a descendant. The node-level term is correctly scoped for the clade; the refinement to phosphatidic acid biosynthesis uses GPAM-specific evidence and is not a propagation failure. Proposed replacements: phosphatidic acid biosynthetic process Supporting Evidence: Reactome:R-HSA-1483166 In the de novo synthesis of phosphatidic acid (PA), lysophosphatidic acid (LPA) is initially formed by the esterification of sn-1 by glycerol 3-phosphate acyltransferase (GPAT) from glycerol 3-phosphate (G3P). |
| GO:0019432 triglyceride biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: Core process; GPAT1 catalyses the first acylation of the glycerol-3-phosphate route to triacylglycerol. Reason: GPAT1 performs a step of the process (acylation of glycerol 3-phosphate), so this is participation, not mere necessity. The IBD at PTN000970957 is seeded by mouse Gpam and human GPAM. Mouse Gpam knockout lowers hepatic and plasma triacylglycerol, and Gpam-null hepatocytes cannot put de novo synthesised fatty acid into triacylglycerol. Mouse Gpam is in the same PANTHER subfamily (SF16) as human GPAM. Supporting Evidence: PMID:12417724 These data confirm the important role of mtGPAT in the synthesis of triacylglycerol PMID:23908354 GPAT1, but not GPAT4, is required to incorporate de novo synthesized fatty acids into TAG and to divert them away from oxidation. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Correct core activity (EC 2.3.1.15, Rhea mappings). Reason: The combined electronic pipeline maps EC 2.3.1.15 and the Rhea glycerol-3-phosphate acylation reactions, which UniProt supports with experimental evidence for this protein. Consistent with the experimental and IBA rows for the same term. Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + hexadecanoyl-CoA = 1-hexadecanoyl- PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0005741 mitochondrial outer membrane | IEA GO_REF:0000044 | ACCEPT | Summary: Correct, specific location; GPAT1 is a peripheral protein of the cytosolic face of the mitochondrial outer membrane. Reason: The UniProt SubCell mapping comes from a curated location backed by the human cryo-EM study. That study also shows how the protein associates with the membrane (amphipathic patch plus N-terminal loop-helix with the targeting signal, no transmembrane helices). Older reviews of rodent GPAT1 report the same compartment. Supporting Evidence: PMID:36522428 GPAT1 has no transmembrane regions as previously proposed but instead associates with the membrane via an amphipathic surface patch and an N-terminal loop-helix region that contains a mitochondrial-targeting signal. PMID:17158253 GPAT1, one of four known glycerol-3-phosphate acyltransferase isoforms, is located on the mitochondrial outer membrane |
| GO:0005886 plasma membrane | IEA GO_REF:0000002 | REMOVE | Summary: Wrong compartment for GPAT1; this location comes from the bacterial PlsB part of the InterPro entry. Reason: The InterPro2GO mapping from IPR028354 (GPAT_PlsB) covers bacterial PlsB, which sits on the cytoplasmic membrane. Animal GPAT1 is a mitochondrial outer membrane protein. Its mitochondrial targeting depends on a basic patch in the N-terminal region (80-120), and mutating that patch abolishes mitochondrial localisation. No study places GPAM at the plasma membrane. This is a lineage-inappropriate electronic transfer, not a second location. Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt outer membrane of hepatic cells via a patch of basic residues. PMID:25415055 GPAT1 and GPAT2 are located in the outer membrane of mitochondria, whereas GPAT3 and GPAT4 are in the ER membrane |
| GO:0006629 lipid metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: True but uninformative; GPAT1's lipid-metabolic role is specifically the first step of phosphatidic acid and triacylglycerol synthesis. Reason: The InterPro-derived root lipid-metabolism term is correct, but GPAM already carries two supported is_a descendants that name what it does. Phosphatidic acid biosynthetic process (GO:0006654) covers the membrane-lipid branch it starts, and triglyceride biosynthetic process (GO:0019432) the storage-lipid branch. Both are listed. Proposed replacements: phosphatidic acid biosynthetic process triglyceride biosynthetic process Supporting Evidence: PMID:25415055 GPATs (EC 2.3.1.15) catalyze the first step in the synthesis of glycerolipids and convert G3P to LPA (1-acyl-GP) by the transfer of a fatty acid from acyl-CoA |
| GO:0008654 phospholipid biosynthetic process | IEA GO_REF:0000002 | MODIFY | Summary: Correct but general; GPAT1's phospholipid-synthetic step is the first step of phosphatidic acid synthesis. Reason: The phospholipid-biosynthesis role is real. GPAT1 makes lysophosphatidic acid, and Gpam-null mice have less palmitate at sn-1 of phosphatidylcholine and phosphatidylethanolamine. The more precise descendant that GPAM already carries is phosphatidic acid biosynthetic process (GO:0006654). Proposed replacements: phosphatidic acid biosynthetic process Supporting Evidence: Reactome:R-HSA-1483166 In the de novo synthesis of phosphatidic acid (PA), lysophosphatidic acid (LPA) is initially formed by the esterification of sn-1 by glycerol 3-phosphate acyltransferase (GPAT) from glycerol 3-phosphate (G3P). |
| GO:0016746 acyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: Correct parent of the established activity; refine to glycerol-3-phosphate O-acyltransferase activity. Reason: The Pfam acyltransferase domain (PF01553/IPR002123) family mapping is true but does not specify donor or acceptor. GPAT1's acceptor is sn-glycerol 3-phosphate and its donor is acyl-CoA, and that is experimentally established. Proposed replacements: glycerol-3-phosphate O-acyltransferase activity Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- |
| GO:0016747 acyltransferase activity, transferring groups other than amino-acyl groups | IEA GO_REF:0000002 | MODIFY | Summary: Correct parent of the established activity; refine to glycerol-3-phosphate O-acyltransferase activity. Reason: The family-level GPAT/DHAPAT mapping (IPR022284) is appropriately broad for a family that also contains DHAP acyltransferases. For GPAM (SF16) the acceptor is glycerol 3-phosphate, so the specific term applies. Proposed replacements: glycerol-3-phosphate O-acyltransferase activity Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- |
| GO:0005515 protein binding | IPI PMID:32296183 A reference map of the human binary protein interactome. | REMOVE | Summary: Bare protein binding from the HuRI binary interactome screen (partner CIDEB, Q9UHD4); uninformative about GPAT1 function. Reason: Under the repository's generic protein-binding policy, GO:0005515 is removed unless the source supports a more informative molecular function. HuRI reports a yeast two-hybrid binary pair, GPAM-CIDEB. It establishes no adaptor, regulatory or complex-forming activity of GPAM. Removing the row does not mean the GPAM-CIDEB interaction is false. A possible functional link between GPAT1 and the CIDE lipid-droplet proteins is raised as a question instead. |
| GO:0006654 phosphatidic acid biosynthetic process | TAS Reactome:R-HSA-1483166 | ACCEPT | Summary: Core process; GPAT1 catalyses the first step of de novo phosphatidic acid synthesis. Reason: GPAT1 performs the first acylation (G3P to LPA) of the two-step de novo route to phosphatidic acid, so it does part of the work of this process. Reactome models this reaction for GPAM at the outer mitochondrial membrane. Supporting Evidence: Reactome:R-HSA-1483166 In the de novo synthesis of phosphatidic acid (PA), lysophosphatidic acid (LPA) is initially formed by the esterification of sn-1 by glycerol 3-phosphate acyltransferase (GPAT) from glycerol 3-phosphate (G3P). Reactome:R-HSA-1482695 Glycerol-3-phosphate (G3P) is acylated to 1-acyl lysophosphatidic acid (LPA) by the enzymes glycerol-3-phosphate acyltransferase 1 (GPAT, also known as GPAM) |
| GO:0019432 triglyceride biosynthetic process | TAS Reactome:R-HSA-75109 | ACCEPT | Summary: Core process; consistent with the IBA and IDA rows for the same term. Reason: Reactome places GPAM in the 'conversion of fatty acyl-CoA to phosphatidic acid' stage of triglyceride biosynthesis. Mouse knockout data show this stage matters physiologically for hepatic triacylglycerol. Supporting Evidence: Reactome:R-HSA-75109 The overall process of triglyceride (triacylglycerol) biosynthesis consists of four biochemical pathways PMID:12417724 These data confirm the important role of mtGPAT in the synthesis of triacylglycerol |
| GO:0016024 CDP-diacylglycerol biosynthetic process | IEA GO_REF:0000041 | KEEP AS NON CORE | Summary: Correct pathway placement (step 1/3 of CDP-diacylglycerol synthesis from glycerol 3-phosphate), but peripheral to GPAT1's main metabolic role. Reason: UniPathway UPA00557 counts glycerol-3-phosphate acylation as step 1 of 3 in CDP-diacylglycerol synthesis, so GPAT1 does catalyse a step of this route. Its lysophosphatidic acid feeds a common phosphatidic acid pool, though. Mouse genetics links GPAT1 mainly to triacylglycerol synthesis and to the sn-1 acyl composition of phospholipids, not specifically to the CDP-DAG branch. The term is precise, but it is a branch the enzyme supplies rather than its defining role. Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP- |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | EXP PMID:18238778 AGPAT6 is a novel microsomal glycerol-3-phosphate acyltransf... | ACCEPT | Summary: Experimental GPAT activity for human GPAM from Chen et al. 2008. The abstract focuses on the paralog AGPAT6/GPAT4, but UniProt cites the full text as ECO:0000269 for GPAM's reactions. Reason: The cached entry is abstract-only and the abstract describes AGPAT6/GPAT4. UniProt nevertheless cites this paper with ECO:0000269 for GPAM's EC 2.3.1.15 reaction and five acyl-CoA-specific reactions (16:0, 18:0, 18:1, 18:2, 12:0). Reactome also cites Chen et al. 2008 for the properties of recombinant human GPAM. Per curation policy, an experimental annotation is not overruled on the basis of an abstract about a paralog. The activity is independently confirmed by the 2023 human structure. Supporting Evidence: Reactome:R-HSA-75886 The biochemical properties and location of human GPAM have been established through studies of the recombinant protein (Chen et al. 2008) file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + octadecanoyl-CoA = 1-octadecanoyl- |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | MODIFY | Summary: High-confidence mitochondrial proteome detection; correct but less specific than the outer membrane location. Reason: The proteomic detection is consistent with GPAT1's location. The known sub-mitochondrial site is the outer membrane, a part_of descendant GPAM already carries, so the term is refined to GO:0005741 (same action as the IBA row for this term). Proposed replacements: mitochondrial outer membrane Supporting Evidence: PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | ISS GO_REF:0000024 | ACCEPT | Summary: Transfer from rat Gpam (P97564), a same-subfamily (SF16) ortholog; consistent with direct human evidence. Reason: Rat Gpam P97564 belongs to PANTHER PTHR12563:SF16 with human GPAM, so the ortholog transfer is phylogenetically grounded. The activity is also directly demonstrated for the human protein. Supporting Evidence: PMID:25415055 GPAT1 localized to the mitochondrial outer membrane and its activity was resistant to NEM, which was consistent with previously characterized mitochondrial GPAT activity. PMID:36522428 Here we present the cryo-EM structures of human GPAT1 in substrate analog-bound and product-bound states. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IMP PMID:19075029 The microsomal cardiolipin remodeling enzyme acyl-CoA lysoca... | ACCEPT | Summary: Experimental annotation from Zhao et al. 2009 (ALCAT1 paper); full text not accessible to this review, but the activity is correct and directly supported elsewhere. Reason: The cached abstract covers ALCAT1, and the PMC full text could not be retrieved programmatically. The curator read the full text; GPAM was presumably assayed there as a comparator acyltransferase, and UniProt cites this paper with ECO:0000269 for a GPAM reaction. The asserted activity is in any case established for human GPAT1, so this row is accepted, deferring to the curator. Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0006651 diacylglycerol biosynthetic process | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: GPAT1 catalyses the first step of the glycerol-3-phosphate route to diacylglycerol; correct but an intermediate of the triacylglycerol pathway rather than a distinct role. Reason: In the de novo (Kennedy) route, diacylglycerol is made from glycerol 3-phosphate through LPA and PA, and GPAT1 catalyses the first of those steps. The transfer from same-subfamily rat Gpam (SF16) is phylogenetically grounded. This is a sub-pathway of the triglyceride synthesis already captured as core, so it is kept as non-core rather than a separate core role. Supporting Evidence: PMID:25415055 GPATs (EC 2.3.1.15) catalyze the first step in the synthesis of glycerolipids and convert G3P to LPA (1-acyl-GP) by the transfer of a fatty acid from acyl-CoA |
| GO:0006654 phosphatidic acid biosynthetic process | ISS GO_REF:0000024 | ACCEPT | Summary: Core process, transferred from same-subfamily rat Gpam and consistent with the Reactome TAS row. Reason: Rat Gpam P97564 is in PANTHER PTHR12563:SF16 with human GPAM. GPAT1 catalyses the LPA-forming first step of de novo phosphatidic acid synthesis. Supporting Evidence: Reactome:R-HSA-1482695 Glycerol-3-phosphate (G3P) is acylated to 1-acyl lysophosphatidic acid (LPA) by the enzymes glycerol-3-phosphate acyltransferase 1 (GPAT, also known as GPAM) |
| GO:0006655 phosphatidylglycerol biosynthetic process | IMP PMID:19075029 The microsomal cardiolipin remodeling enzyme acyl-CoA lysoca... | KEEP AS NON CORE | Summary: Experimental annotation tied to a curated GPAM lysophosphatidylglycerol acyltransferase reaction (RHEA:33203); plausible but a secondary activity outside GPAT1's established role. Reason: UniProt records, with ECO:0000269 to this paper, a GPAM reaction that acylates 1-acyl-lysophosphatidylglycerol to diacyl-phosphatidylglycerol. The curator therefore had experimental grounds. The full text was not accessible here and the cached abstract is about ALCAT1, so the row is not overruled. A lysophosphatidylglycerol acyltransferase side activity (Lands-cycle remodelling) is peripheral to GPAT1's main role of acylating glycerol 3-phosphate. It has not been reproduced in the structural study, and its physiological weight is unknown, so it is kept as non-core. Supporting Evidence: file:human/GPAM/GPAM-uniprot.txt Reaction=1-acyl-sn-glycero-3-phospho-(1'-sn-glycerol) + an acyl-CoA = a |
| GO:0005741 mitochondrial outer membrane | TAS Reactome:R-HSA-1482695 | ACCEPT | Summary: Correct; Reactome places the GPAT1 reaction at the outer mitochondrial membrane. Reason: Consistent with the human structural study and curated UniProt location. Supporting Evidence: Reactome:R-HSA-1482695 at the outer mitochondrial (OM) membrane PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0005741 mitochondrial outer membrane | TAS Reactome:R-HSA-1655837 | ACCEPT | Summary: Correct location of the GPAM protein product; the source reaction is an expression event. Reason: Reactome places the translated GPAM product in the outer mitochondrial membrane compartment for its expression event. The location assertion itself is correct and consistent with the other rows. Supporting Evidence: PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0005741 mitochondrial outer membrane | TAS Reactome:R-HSA-75886 | ACCEPT | Summary: Correct; Reactome's GPAM/GPAT2 reaction is modelled on the outer mitochondrial membrane. Reason: Consistent with the human structural study and curated UniProt location. Supporting Evidence: Reactome:R-HSA-75886 associated with the outer mitochondrial membrane catalyzes the reaction of cytosolic glycerol 3-phosphate and acyl-CoA to form 1-acylglycerol 3-phosphate and CoASH |
| GO:0005741 mitochondrial outer membrane | TAS Reactome:R-HSA-8932020 | ACCEPT | Summary: Correct location of the GPAM product; the source event is RUNX1/ESR1 stimulation of GPAM expression. Reason: The location of the gene product is correct regardless of the transcriptional event it was modelled in. No regulatory process term is asserted for GPAM from this row. Supporting Evidence: PMID:36522428 Glycerol-3-phosphate acyltransferase (GPAT)1 is a mitochondrial outer membrane protein that catalyzes the first step of de novo glycerolipid biosynthesis. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IMP PMID:18238778 AGPAT6 is a novel microsomal glycerol-3-phosphate acyltransf... | ACCEPT | Summary: Experimental GPAT activity for GPAM from Chen et al. 2008; consistent with the EXP row and the structural study. Reason: Same paper and reasoning as the EXP row. UniProt and Reactome both cite this paper for human GPAM's activity, and the abstract's paralog focus is not grounds to overrule the curator. Supporting Evidence: Reactome:R-HSA-75886 The biochemical properties and location of human GPAM have been established through studies of the recombinant protein (Chen et al. 2008) |
| GO:0019432 triglyceride biosynthetic process | IDA PMID:18238778 AGPAT6 is a novel microsomal glycerol-3-phosphate acyltransf... | ACCEPT | Summary: Experimental support for GPAT1's role in triacylglycerol synthesis; consistent with mouse knockout data. Reason: The full text was not accessible here. GPAT1 catalyses the first step of glycerol-3-phosphate-pathway triacylglycerol synthesis, and loss of the same-subfamily mouse ortholog reduces hepatic triacylglycerol, so the experimental row is retained. Supporting Evidence: PMID:12417724 These data confirm the important role of mtGPAT in the synthesis of triacylglycerol PMID:23908354 GPAT1, but not GPAT4, is required to incorporate de novo synthesized fatty acids into TAG and to divert them away from oxidation. |
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Download this section (compressed HTML)Q: Does the HuRI GPAM-CIDEB binary interaction reflect a functional association at mitochondria-lipid droplet contacts, given that CIDE proteins act on lipid droplets in hepatocytes where GPAT1 drives triacylglycerol synthesis?
Q: Is the lysophosphatidylglycerol acyltransferase activity attributed to GPAM (RHEA:33203) a physiologically relevant activity of the native enzyme, or a side activity of overexpressed protein?
Q: How does lysophosphatidic acid made by GPAT1 on the outer mitochondrial membrane reach the ER-resident AGPAT, lipin and DGAT enzymes that complete phosphatidic acid and triacylglycerol synthesis?
Experiment: Assay purified human GPAT1 for acylation of 1-acyl-lysophosphatidylglycerol versus glycerol 3-phosphate under matched conditions, and test catalytic HXXXXD mutants (H230A, D235A), to establish whether the lysophospholipid acyltransferase activity is intrinsic.
Type: in vitro enzyme kinetics
Experiment: Co-immunoprecipitation and proximity labelling of endogenous GPAT1 with CIDEB in hepatocytes, combined with lipidomics after CIDEB loss, to test whether the HuRI interaction has a role in channelling GPAT1 products to lipid droplets.
Type: proximity labelling / lipidomics
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