EPT1

UniProt ID: P22140
Organism: Saccharomyces cerevisiae S288C
Review Status: DRAFT
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Gene Description

Ept1 (YHR123W) is the sn-1,2-diacylglycerol ethanolaminephosphotransferase of Saccharomyces cerevisiae (EC 2.7.8.1), a polytopic membrane enzyme of the CDP-alcohol phosphatidyltransferase family. It transfers phosphoethanolamine from CDP-ethanolamine to diacylglycerol, releasing CMP, in the final step of the CDP-ethanolamine (Kennedy) branch of phosphatidylethanolamine synthesis. Ept1 has broad aminoalcohol specificity and also uses CDP-monomethylethanolamine, CDP-dimethylethanolamine and CDP-choline in vitro (EC 2.7.8.2), but the paralog Cpt1 is the main cholinephosphotransferase in vivo. Ept1 resides in endomembranes (ER and Golgi), requires Mg2+ and phospholipid activators, is inhibited by CMP, and is not essential for growth.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0000139 Golgi membrane
IEA
GO_REF:0000044 		ACCEPT
Summary: UniProt subcellular location (Golgi apparatus membrane; multi-pass) mapped via SL-0134. Consistent with the Golgi GFP HDA; Ept1 is an integral endomembrane enzyme.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0004142 diacylglycerol cholinephosphotransferase activity
EXP
PMID:1847919
sn-1,2-diacylglycerol choline- and ethanolaminephosphotransf... 		KEEP AS NON CORE
Summary: Hjelmstad & Bell 1991 mixed-micelle assays show Ept1 uses CDP-choline in addition to CDP-ethanolamine. Genuine activity, but Cpt1 is the dominant cholinephosphotransferase in vivo.
Reason: Secondary substrate; Ept1's physiological role is PE synthesis.
Supporting Evidence:
PMID:1847919
The EPT1 gene product utilized CDP-ethanolamine, -monomethylethanolamine, -dimethylethanolamine, and -choline to significant extents
GO:0004142 diacylglycerol cholinephosphotransferase activity
IDA
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		KEEP AS NON CORE
Summary: Membranes from EPT1-overexpressing strains show elevated CMP-sensitive cholinephosphotransferase activity; Ept1 has dual specificity.
Reason: Secondary activity relative to ethanolaminephosphotransferase.
Supporting Evidence:
PMID:2848840
the EPT1 gene product possesses both ethanolamine- and cholinephosphotransferase activities
GO:0004142 diacylglycerol cholinephosphotransferase activity
IEA
GO_REF:0000120 		KEEP AS NON CORE
Summary: Combined IEA from ARBA/RHEA:32939/EC 2.7.8.2. Correct secondary activity of Ept1.
Reason: Secondary activity.
Supporting Evidence:
PMID:2848840
the EPT1 gene product possesses both ethanolamine- and cholinephosphotransferase activities
GO:0004142 diacylglycerol cholinephosphotransferase activity
IMP
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		KEEP AS NON CORE
Summary: ept1 mutant membranes have 3.5-7-fold reduced cholinephosphotransferase activity. Supports dual specificity.
Reason: Secondary activity.
Supporting Evidence:
PMID:2848840
The sn-1,2-diacylglycerol cholinephosphotransferase activities in membranes prepared from ept1 mutants were reduced 3.5- to 7-fold.
GO:0004307 ethanolaminephosphotransferase activity
EXP
PMID:1847919
sn-1,2-diacylglycerol choline- and ethanolaminephosphotransf... 		ACCEPT
Summary: Kinetic characterization of Ept1 in cpt1 membranes (mixed micelles) with CDP-ethanolamine. Core activity.
Supporting Evidence:
PMID:1847919
The Saccharomyces cerevisiae CPT1 and EPT1 genes are structural genes encoding distinct sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases.
PMID:1847919
The EPT1 gene product utilized CDP-ethanolamine, -monomethylethanolamine, -dimethylethanolamine, and -choline to significant extents
GO:0004307 ethanolaminephosphotransferase activity
IDA
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		ACCEPT
Summary: EPT1 overexpression raises membrane ethanolaminephosphotransferase activity 22-33-fold. Core activity.
Supporting Evidence:
PMID:2848840
In strains transformed with a multicopy EPT1-bearing plasmid, a 22- to 33-fold overproduction of ethanolaminephosphotransferase activity was observed.
GO:0004307 ethanolaminephosphotransferase activity
IEA
GO_REF:0000120 		ACCEPT
Summary: RHEA:32943 / EC 2.7.8.1 mapping. Matches experimental data.
Supporting Evidence:
PMID:1847919
The Saccharomyces cerevisiae CPT1 and EPT1 genes are structural genes encoding distinct sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases.
GO:0004307 ethanolaminephosphotransferase activity
IMP
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		ACCEPT
Summary: ept1 mutant membranes have 30-90-fold reduced ethanolaminephosphotransferase activity.
Supporting Evidence:
PMID:2848840
The ethanolaminephosphotransferase activities in membranes prepared from ept1 and ept2 mutants were reduced 30- to 90-fold
GO:0004307 ethanolaminephosphotransferase activity
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways (PHOS-PWY / PWY3O-2 / PWY3O-259) assigns Ept1 to DAG + CDP-ethanolamine -> PE + CMP (EC 2.7.8.1). Correct step.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0004307 ethanolaminephosphotransferase activity
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways (PHOS-PWY / PWY3O-2 / PWY3O-259) assigns Ept1 to DAG + CDP-ethanolamine -> PE + CMP (EC 2.7.8.1). Correct step.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0004307 ethanolaminephosphotransferase activity
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways (PHOS-PWY / PWY3O-2 / PWY3O-259) assigns Ept1 to DAG + CDP-ethanolamine -> PE + CMP (EC 2.7.8.1). Correct step.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0005515 protein binding
IPI
PMID:18467557
An in vivo map of the yeast protein interactome. 		REMOVE
Summary: Genome-wide protein-fragment complementation screen detected Ept1 with its paralog Cpt1 (P17898). Bare protein binding gives no functional information; whether Cpt1/Ept1 form a functional hetero-oligomer is untested.
Reason: Bare protein binding carries no functional information; removal does not dispute the Ept1-Cpt1 interaction.
GO:0005515 protein binding
IPI
PMID:31454312
The role of structural pleiotropy and regulatory evolution i... 		REMOVE
Summary: Paralog-interaction study (structural pleiotropy and paralog retention) recorded Ept1-Cpt1 interaction. Interesting for paralog evolution but 'protein binding' is not a function.
Reason: Bare protein binding carries no functional information; removal does not dispute the Ept1-Cpt1 interaction.
GO:0005515 protein binding
IPI
PMID:37968396
The social and structural architecture of the yeast protein ... 		REMOVE
Summary: Proteome-scale interactome (Michaelis et al. 2023) recorded Ept1-Cpt1. Uninformative term.
Reason: Bare protein binding carries no functional information; removal does not dispute the Ept1-Cpt1 interaction.
GO:0005783 endoplasmic reticulum
HDA
PMID:26928762
One library to make them all: streamlining the creation of y... 		ACCEPT
Summary: SWAT/high-throughput GFP library (Yofe et al. 2016) places Ept1 in the ER, consistent with an integral endomembrane CDP-alcohol phosphotransferase that acts on ER diacylglycerol.
Supporting Evidence:
PMID:26928762
we found that most new localization assignments were to the ER, punctate structures and vacuole
GO:0005794 Golgi apparatus
HDA
PMID:14562095
Global analysis of protein localization in budding yeast. 		ACCEPT
Summary: Huh et al. 2003 GFP survey found Ept1-GFP at Golgi; consistent with UniProt Golgi membrane.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0005829 cytosol
RCA
GO_REF:0000123 		REMOVE
Summary: YeastPathways RCA default places the reaction in the cytosol. Ept1 is a polytopic integral membrane protein that acts on membrane diacylglycerol in ER/Golgi; is_active_in cytosol is incorrect.
Reason: Localization default of the pathway-to-GO-CAM conversion; contradicted by membrane topology and localization data.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0005829 cytosol
RCA
GO_REF:0000123 		REMOVE
Summary: YeastPathways RCA default places the reaction in the cytosol. Ept1 is a polytopic integral membrane protein that acts on membrane diacylglycerol in ER/Golgi; is_active_in cytosol is incorrect.
Reason: Localization default of the pathway-to-GO-CAM conversion; contradicted by membrane topology and localization data.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0005829 cytosol
RCA
GO_REF:0000123 		REMOVE
Summary: YeastPathways RCA default places the reaction in the cytosol. Ept1 is a polytopic integral membrane protein that acts on membrane diacylglycerol in ER/Golgi; is_active_in cytosol is incorrect.
Reason: Localization default of the pathway-to-GO-CAM conversion; contradicted by membrane topology and localization data.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0006646 phosphatidylethanolamine biosynthetic process
IDA
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		ACCEPT
Summary: Ept1 provides most ethanolaminephosphotransferase activity, the final step of CDP-ethanolamine PE synthesis.
Supporting Evidence:
PMID:2848840
In strains transformed with a multicopy EPT1-bearing plasmid, a 22- to 33-fold overproduction of ethanolaminephosphotransferase activity was observed.
GO:0006646 phosphatidylethanolamine biosynthetic process
IEA
GO_REF:0000041 		ACCEPT
Summary: UniPathway UPA00558 mapping (PE from ethanolamine). Correct.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0006646 phosphatidylethanolamine biosynthetic process
IMP
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		ACCEPT
Summary: ept1 mutants lack most ethanolaminephosphotransferase activity of the CDP-ethanolamine pathway.
Supporting Evidence:
PMID:2848840
The ethanolaminephosphotransferase activities in membranes prepared from ept1 and ept2 mutants were reduced 30- to 90-fold
GO:0006656 phosphatidylcholine biosynthetic process
IDA
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		KEEP AS NON CORE
Summary: Ept1 can make PC from CDP-choline in vitro, but UniProt notes it does not substantially contribute to PC synthesis in vivo (Cpt1 does).
Reason: Minor contribution; core process is PE synthesis.
Supporting Evidence:
PMID:2848840
the EPT1 gene product possesses both ethanolamine- and cholinephosphotransferase activities
GO:0006656 phosphatidylcholine biosynthetic process
IEA
GO_REF:0000120 		KEEP AS NON CORE
Summary: ARBA/UniPathway UPA00753 (PC biosynthesis) mapping, driven by the EC 2.7.8.2 activity. Minor in vivo role.
Reason: Secondary activity.
Supporting Evidence:
PMID:2848840
the EPT1 gene product possesses both ethanolamine- and cholinephosphotransferase activities
GO:0006656 phosphatidylcholine biosynthetic process
IMP
PMID:2848840
The sn-1,2-diacylglycerol ethanolaminephosphotransferase act... 		KEEP AS NON CORE
Summary: ept1 reduces membrane cholinephosphotransferase activity modestly; contribution to PC synthesis is minor.
Reason: Secondary role.
Supporting Evidence:
PMID:2848840
The sn-1,2-diacylglycerol cholinephosphotransferase activities in membranes prepared from ept1 mutants were reduced 3.5- to 7-fold.
GO:0008654 phospholipid biosynthetic process
IEA
GO_REF:0000002 		ACCEPT
Summary: InterPro IPR000462 (CDP-alcohol phosphatidyltransferase) to phospholipid biosynthetic process. Correct general term.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0008654 phospholipid biosynthetic process
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways superpathway RCA to phospholipid biosynthetic process. Correct general term.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0008654 phospholipid biosynthetic process
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways superpathway RCA to phospholipid biosynthetic process. Correct general term.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route
GO:0016020 membrane
IEA
GO_REF:0000002 		TOO GENERAL
Summary: InterPro IPR000462 to membrane. Correct but general; Ept1 is an integral ER/Golgi membrane protein.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
SUBCELLULAR LOCATION: Golgi apparatus membrane; Multi-pass membrane
GO:0016780 phosphotransferase activity, for other substituted phosphate groups
IEA
GO_REF:0000002 		MODIFY
Summary: InterPro IPR000462 to the generic 'phosphotransferase activity, for other substituted phosphate groups'. Correct parent; specific activity is known.
Reason: Replace with the specific experimentally supported activity.
Supporting Evidence:
PMID:1847919
The Saccharomyces cerevisiae CPT1 and EPT1 genes are structural genes encoding distinct sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases.
GO:0046474 glycerophospholipid biosynthetic process
RCA
GO_REF:0000123 		ACCEPT
Summary: YeastPathways Kennedy pathway (PWY3O-259) RCA to glycerophospholipid biosynthetic process. Correct general term.
Supporting Evidence:
file:yeast/EPT1/EPT1-uniprot.txt
Catalyzes the final step in the CDP-ethanolamine route

Core Functions

Transfer of phosphoethanolamine from CDP-ethanolamine to sn-1,2-diacylglycerol, the terminal step of the CDP-ethanolamine branch of the Kennedy pathway; broad specificity also allows use of CDP-choline and methylated CDP-ethanolamines.

Molecular Function:
ethanolaminephosphotransferase activity
Directly Involved In:
phosphatidylethanolamine biosynthetic process
Cellular Locations:
endoplasmic reticulum Golgi membrane
Supporting Evidence:
  • PMID:1847919
    The Saccharomyces cerevisiae CPT1 and EPT1 genes are structural genes encoding distinct sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases.
  • PMID:2848840
    The ethanolaminephosphotransferase activities in membranes prepared from ept1 and ept2 mutants were reduced 30- to 90-fold
  • PMID:2848840
    In strains transformed with a multicopy EPT1-bearing plasmid, a 22- to 33-fold overproduction of ethanolaminephosphotransferase activity was observed.

References

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Deep Research

SGD

(EPT1-deep-research-sgd.md)
SGD gene description for EPT1 (yeast) SGD

SGD gene description for EPT1 (yeast)

sn-1,2-diacylglycerol ethanolamine- and cholinephosphotranferase; not essential for viability; EPT1 has a paralog, CPT1, that arose from the whole genome duplication

📚 Additional Documentation

Notes

(EPT1-notes.md)

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