SCT1 (also called GAT2) encodes one of the two redundant glycerol-3-phosphate O-acyltransferases (GPATs) of budding yeast. These are dual-substrate sn-1 acyltransferases that transfer an acyl chain from acyl-CoA to sn-glycerol 3-phosphate (making lysophosphatidic acid) or to dihydroxyacetone phosphate, catalysing the first and committed step of de novo glycerophospholipid and triacylglycerol synthesis. Sct1 prefers glycerol 3-phosphate over DHAP and has a marked preference for 16-carbon acyl-CoAs. By drawing C16:0-CoA into glycerolipids it competes with the desaturase Ole1 and so influences fatty-acid saturation. Metabolic labelling identifies Sct1 as the main supplier of diacylglycerol for TAG and for phosphatidylcholine made by the CDP-choline (Kennedy) route. Sct1 is a multi-pass membrane protein of the perinuclear and cortical ER and is a phosphoprotein. SCT1 is synthetically lethal with GPT2/GAT1. It was first identified as a suppressor of a choline transport defect.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for glycerol-3-phosphate O-acyltransferase activity at the fungal GPAT node (PTN000787962), grounded in Sct1/Gat2 and Gpt2/Gat1. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IDA PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IDA from Zheng and Zou 2001; biochemical assays show Gat2p/Sct1p is a G3P/DHAP sn-1 acyltransferase with a C16 acyl-CoA preference. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases PMID:11544256 In contrast, Gat2p(Sct1p) displayed preference toward 16-carbon fatty acids. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from RHEA/EC 2.3.1.15 mapping derived from UniProt's GPAT reactions for Sct1. Correct. Supporting Evidence: file:yeast/SCT1/SCT1-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IMP PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IMP from Zheng and Zou 2001; disruption of YBL011w/SCT1 substantially decreased total cellular GPAT activity. Supporting Evidence: PMID:11544256 Disruption of the open reading frame YBL011w, corresponding to a gene previously identified as a choline transporter suppressor (SCT1), resulted in a substantial decrease of total cellular G-3-P acyltransferase activity. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA rows (PWY3O-6499 glycerol-3-phosphate pathway, PWY3O-6635 superpathway, TRIGLSYN-PWY) assigning the G3P + acyl-CoA -> LPA step (EC 2.3.1.15) to Sct1. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. PMID:19525420 Gat2p is the primary supplier of DAG, used mainly in triacylglycerol synthesis and phosphatidylcholine synthesis through the CDP-choline pathway |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA rows (PWY3O-6499 glycerol-3-phosphate pathway, PWY3O-6635 superpathway, TRIGLSYN-PWY) assigning the G3P + acyl-CoA -> LPA step (EC 2.3.1.15) to Sct1. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. PMID:19525420 Gat2p is the primary supplier of DAG, used mainly in triacylglycerol synthesis and phosphatidylcholine synthesis through the CDP-choline pathway |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA rows (PWY3O-6499 glycerol-3-phosphate pathway, PWY3O-6635 superpathway, TRIGLSYN-PWY) assigning the G3P + acyl-CoA -> LPA step (EC 2.3.1.15) to Sct1. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. PMID:19525420 Gat2p is the primary supplier of DAG, used mainly in triacylglycerol synthesis and phosphatidylcholine synthesis through the CDP-choline pathway |
| GO:0005783 endoplasmic reticulum | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: HDA from the Huh et al. 2003 GFP survey (ER). Supporting Evidence: PMID:14562095 expressing full-length, chromosomally tagged green fluorescent protein fusion proteins PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: HDA from the SWAT N-terminal GFP endomembrane library (Yofe et al. 2016) (ER). Supporting Evidence: PMID:26928762 carrying SWAT-GFP modules at the amino termini of endomembrane proteins PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA (is_active_in ER) for the fungal GPAT clade. Correct. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | IDA PMID:19525420 Glycerol-3-phosphate acyltransferases gat1p and gat2p are mi... | ACCEPT | Summary: IDA from Bratschi et al. 2009; microscopy and density-gradient fractionation show Gat2p in perinuclear and cortical ER. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005789 endoplasmic reticulum membrane | EXP PMID:19525420 Glycerol-3-phosphate acyltransferases gat1p and gat2p are mi... | ACCEPT | Summary: SGD EXP from Bratschi et al. 2009 (ER membrane). Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: IEA from UniProt subcellular location (SL-0097 ER membrane). Correct. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Sct1 is a multi-pass ER membrane protein. Reason: The cytosol location is a pathway default that contradicts the experimentally established ER membrane localisation. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Sct1 is a multi-pass ER membrane protein. Reason: The cytosol location is a pathway default that contradicts the experimentally established ER membrane localisation. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Sct1 is a multi-pass ER membrane protein. Reason: The cytosol location is a pathway default that contradicts the experimentally established ER membrane localisation. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Sct1 is a multi-pass ER membrane protein. Reason: The cytosol location is a pathway default that contradicts the experimentally established ER membrane localisation. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0006644 phospholipid metabolic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: IEA from ARBA rule ARBA00028721 for phospholipid metabolic process. Correct but general. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0006654 phosphatidic acid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6635) for phosphatidic acid biosynthetic process; sct1 cells have a smaller PA pool. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. PMID:11544256 The most notable of the altered phospholipid compositions of the gat1Delta and gat2(sct1)Delta strains are a decreased phosphatidic acid pool |
| GO:0008654 phospholipid biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for phospholipid biosynthetic process at the fungal GPAT node. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0008654 phospholipid biosynthetic process | IMP PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IMP from Zheng and Zou 2001; sct1 deletion altered phospholipid composition, with less PA and a higher PS/PI ratio. Supporting Evidence: PMID:11544256 The most notable of the altered phospholipid compositions of the gat1Delta and gat2(sct1)Delta strains are a decreased phosphatidic acid pool |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6499 G3P pathway) for phospholipid biosynthetic process; Sct1 catalyses the first acylation. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6499 G3P pathway) for phospholipid biosynthetic process; Sct1 catalyses the first acylation. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0016024 CDP-diacylglycerol biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: IEA from UniPathway UPA00557 (CDP-diacylglycerol from sn-glycerol 3-phosphate, step 1/3). Sct1 catalyses that first step. Supporting Evidence: file:yeast/SCT1/SCT1-uniprot.txt PATHWAY: Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP- |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for glycerone-phosphate O-acyltransferase activity at the fungal GPAT node. Correct; Sct1 is dual-substrate, though G3P is preferred. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases file:yeast/SCT1/SCT1-uniprot.txt triacylglycerols (TAGs). Prefers Gly-3-P over dihydroxyacetone |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IDA PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IDA from Zheng and Zou 2001; Gat2p/Sct1p acylates DHAP as well as G3P. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from RHEA/EC 2.3.1.42 mapping derived from UniProt's DHAP acyltransferase reaction. Correct. Supporting Evidence: file:yeast/SCT1/SCT1-uniprot.txt Reaction=dihydroxyacetone phosphate + an acyl-CoA = a 1-acylglycerone |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6635) assigning the DHAP + acyl-CoA -> 1-acyl-DHAP step (EC 2.3.1.42) to Sct1. Supported by its dual-substrate activity. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6635) assigning the DHAP + acyl-CoA -> 1-acyl-DHAP step (EC 2.3.1.42) to Sct1. Supported by its dual-substrate activity. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016746 acyltransferase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: IEA from InterPro IPR002123 (phospholipid/glycerol acyltransferase domain) for acyltransferase activity. Correct but general. Supporting Evidence: file:yeast/SCT1/SCT1-uniprot.txt SIMILARITY: Belongs to the GPAT/DAPAT family. |
| GO:0019432 triglyceride biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (TRIGLSYN-PWY) for triglyceride biosynthetic process. Sct1 makes the first intermediate of de novo TAG synthesis and is the primary supplier of DAG for TAG. Supporting Evidence: PMID:19525420 Gat2p is the primary supplier of DAG, used mainly in triacylglycerol synthesis and phosphatidylcholine synthesis through the CDP-choline pathway |
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Download this section (compressed HTML)Q: Is the Sct1 versus Gpt2 split in channelling acyl chains to TAG and PC explained by acyl-CoA selectivity alone, or by distinct ER subdomains and partner enzymes?
Q: Is the DHAP acyltransferase activity of Sct1 physiologically significant, given its preference for glycerol 3-phosphate?
Experiment: Express chimeric Sct1/Gpt2 proteins swapping acyl-CoA binding regions and measure C16:0 versus C18:1 incorporation into LPA, TAG and PC in a gat1 sct1 background rescued by each chimera.
Hypothesis: Acyl-CoA selectivity determinants explain why Sct1 is the main supplier of saturated DAG for TAG and Kennedy-pathway PC.
Type: biochemistry/genetics
Glycerol 3-phosphate/dihydroxyacetone phosphate sn-1 acyltransferase; dual substrate-specific acyltransferase of the glycerolipid biosynthesis pathway; prefers 16-carbon fatty acids; similar to Gpt2p; gene is constitutively transcribed
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