Opi3 (Pem2, YJR073C) is the phospholipid N-methyltransferase (PLMT) of Saccharomyces cerevisiae, a small polytopic membrane protein of the PEMT family that uses S-adenosyl-L-methionine to methylate phosphatidyl-N-monomethylethanolamine to phosphatidyl-N,N-dimethylethanolamine and then to phosphatidylcholine (EC 2.1.1.71), the second and third steps of the CDP-diacylglycerol (PE methylation) route to PC; the first methylation of PE is performed mainly by Cho2/Pem1, although Opi3 can also catalyse it at a low rate. Opi3 is an ER membrane protein, has been detected in mitochondrial and cell-periphery fractions, and opi3 mutants accumulate methylated PE intermediates, overproduce and excrete inositol, and depend on exogenous choline (Kennedy pathway) to maintain normal PC levels.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | EXP PMID:2198947 Phosphatidylethanolamine methyltransferase and phospholipid ... | ACCEPT | Summary: Gaynor & Carman 1990 characterized the PLMT (Opi3) activity in cho2 disruptant microsomes: second and third methylations with defined Km for PMME and PDME. Core activity. Supporting Evidence: PMID:2198947 phospholipid methyltransferase (PLMT) catalyzes the second two methylation reactions |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | EXP PMID:22001639 Quantitative profiling of PE, MMPE, DMPE, and PC lipid speci... | ACCEPT | Summary: Bilgin et al. 2011 used mass-tag lipidomics with labelled ethanolamine to survey PE-methylation enzyme activities and substrate specificities in yeast mutants. Supports Opi3 methylation of MMPE/DMPE; abstract-only, curator assay accepted. Supporting Evidence: PMID:22001639 to survey the activities and substrate specificities of enzymes involved in PE metabolism in Saccharomyces cerevisiae |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000397368 (fungal and plant PLMTs incl. S. pombe and Arabidopsis members, and Opi3 itself). Core activity. Supporting Evidence: PMID:2445736 the membrane fraction from the transformants carrying PEM2 catalyzed the synthesis of phosphatidylcholine (PC) from PE, indicating that it contains all of the three methylation activities PMID:2684666 the PEM2-encoded methyltransferase exhibited a somewhat broader specificity with a preference for the second and third steps of the pathway |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IDA PMID:2445736 Yeast phosphatidylethanolamine methylation pathway. Cloning ... | ACCEPT | Summary: Kodaki & Yamashita 1987: PEM2 transformant membranes convert PE to PC, preferring PMME and PDME. Core activity. Supporting Evidence: PMID:2445736 the membrane fraction from the transformants carrying PEM2 catalyzed the synthesis of phosphatidylcholine (PC) from PE, indicating that it contains all of the three methylation activities PMID:2445736 PMME and phosphatidyl-N,N-dimethylethanolamine were found to be utilized more preferentially than PE. |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from RHEA:32735/32739, EC 2.1.1.71 and UniRule (HAMAP MF_03216). Correct. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt Catalyzes the second two steps of the methylation pathway of |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IGI PMID:2445736 Yeast phosphatidylethanolamine methylation pathway. Cloning ... | ACCEPT | Summary: IGI with CHO2/PEM1 (S000003389): expression of PEM2 in a pem1 pem2 background reconstitutes the later methylations. Core activity. Supporting Evidence: PMID:2445736 the membrane fraction from the transformants carrying PEM2 catalyzed the synthesis of phosphatidylcholine (PC) from PE, indicating that it contains all of the three methylation activities |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | IMP PMID:2684666 Characterization of the methyltransferases in the yeast phos... | ACCEPT | Summary: pem2 disruption abolishes the second and third methylation activities. Core activity. Supporting Evidence: PMID:2684666 When the PEM2 locus was disrupted, the activities for the second and third methylations were totally lost, but that for the first methylation remained. |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways (PHOS-PWY, PHOSLIPSYN2-PWY-1) assigns Opi3 to SAM-dependent methylation of PMME and PDME (EC 2.1.1.71). Correct. Supporting Evidence: PMID:2198947 phospholipid methyltransferase (PLMT) catalyzes the second two methylation reactions |
| GO:0000773 phosphatidyl-N-methylethanolamine N-methyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways (PHOS-PWY, PHOSLIPSYN2-PWY-1) assigns Opi3 to SAM-dependent methylation of PMME and PDME (EC 2.1.1.71). Correct. Supporting Evidence: PMID:2198947 phospholipid methyltransferase (PLMT) catalyzes the second two methylation reactions |
| GO:0004608 phosphatidylethanolamine N-methyltransferase activity | EXP PMID:22001639 Quantitative profiling of PE, MMPE, DMPE, and PC lipid speci... | KEEP AS NON CORE | Summary: Opi3 can catalyse the first methylation (PE -> PMME) at a low rate; residual first-step activity in pem1/cho2 mutants depends on Opi3, but Cho2 is the main PE N-methyltransferase. Reason: Real but minor activity; Opi3's physiological role is the second and third methylations. Supporting Evidence: PMID:2684666 When the PEM1 locus was disrupted, the activity for the first methylation was greatly decreased but was still detectable, while the activities for the second and third methylations were well retained. PMID:2684666 When the PEM2 locus was disrupted, the activities for the second and third methylations were totally lost, but that for the first methylation remained. |
| GO:0004608 phosphatidylethanolamine N-methyltransferase activity | EXP PMID:2445736 Yeast phosphatidylethanolamine methylation pathway. Cloning ... | KEEP AS NON CORE | Summary: Opi3 can catalyse the first methylation (PE -> PMME) at a low rate; residual first-step activity in pem1/cho2 mutants depends on Opi3, but Cho2 is the main PE N-methyltransferase. Reason: Real but minor activity; Opi3's physiological role is the second and third methylations. Supporting Evidence: PMID:2684666 When the PEM1 locus was disrupted, the activity for the first methylation was greatly decreased but was still detectable, while the activities for the second and third methylations were well retained. PMID:2684666 When the PEM2 locus was disrupted, the activities for the second and third methylations were totally lost, but that for the first methylation remained. |
| GO:0004608 phosphatidylethanolamine N-methyltransferase activity | EXP PMID:2684666 Characterization of the methyltransferases in the yeast phos... | KEEP AS NON CORE | Summary: Opi3 can catalyse the first methylation (PE -> PMME) at a low rate; residual first-step activity in pem1/cho2 mutants depends on Opi3, but Cho2 is the main PE N-methyltransferase. Reason: Real but minor activity; Opi3's physiological role is the second and third methylations. Supporting Evidence: PMID:2684666 When the PEM1 locus was disrupted, the activity for the first methylation was greatly decreased but was still detectable, while the activities for the second and third methylations were well retained. PMID:2684666 When the PEM2 locus was disrupted, the activities for the second and third methylations were totally lost, but that for the first methylation remained. |
| GO:0004608 phosphatidylethanolamine N-methyltransferase activity | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: RHEA:11164 / EC 2.1.1.17 mapping from UniProt. Correct minor activity. Reason: Secondary activity. Supporting Evidence: PMID:2684666 When the PEM1 locus was disrupted, the activity for the first methylation was greatly decreased but was still detectable, while the activities for the second and third methylations were well retained. |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | KEEP AS NON CORE | Summary: Detected in purified mitochondria by mass spectrometry. Could reflect ER-mitochondria contact (MAM) association; ER is the established site of activity. Reason: High-throughput proteomic detection; not the main site of function. |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | KEEP AS NON CORE | Summary: Detected in purified mitochondria by mass spectrometry. Could reflect ER-mitochondria contact (MAM) association; ER is the established site of activity. Reason: High-throughput proteomic detection; not the main site of function. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: High-throughput GFP library localizes Opi3 to the ER, consistent with microsomal PE-methylation activity. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: IBA is_active_in ER from PTN000397368 (incl. human PEMT). Consistent with yeast data. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | EXP PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: GFP localization (Huh et al. 2003) to ER membrane for a multi-pass membrane protein. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt subcellular location/UniRule mapping to ER membrane. Correct. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA places the methylation steps in the cytosol. Opi3 is an integral ER membrane protein acting on membrane phospholipids, so is_active_in cytosol is incorrect. Reason: Localization default of the pathway conversion; contradicted by membrane localization. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA places the methylation steps in the cytosol. Opi3 is an integral ER membrane protein acting on membrane phospholipids, so is_active_in cytosol is incorrect. Reason: Localization default of the pathway conversion; contradicted by membrane localization. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA places the methylation steps in the cytosol. Opi3 is an integral ER membrane protein acting on membrane phospholipids, so is_active_in cytosol is incorrect. Reason: Localization default of the pathway conversion; contradicted by membrane localization. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum membrane |
| GO:0006656 phosphatidylcholine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000397368. Opi3 performs the final methylations that yield PC. Supporting Evidence: PMID:6337128 The Saccharomyces cerevisiae opi3-3 mutant was shown to be defective in the synthesis of phosphatidylcholine via methylation of phosphatidylethanolamine. |
| GO:0006656 phosphatidylcholine biosynthetic process | IDA PMID:2445736 Yeast phosphatidylethanolamine methylation pathway. Cloning ... | ACCEPT | Summary: PEM2 transformant membranes synthesize PC from PE. Supporting Evidence: PMID:2445736 the membrane fraction from the transformants carrying PEM2 catalyzed the synthesis of phosphatidylcholine (PC) from PE, indicating that it contains all of the three methylation activities |
| GO:0006656 phosphatidylcholine biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro/UniRule/UniPathway UPA00753 mapping to PC biosynthesis. Correct. Supporting Evidence: file:yeast/OPI3/OPI3-uniprot.txt Catalyzes the second two steps of the methylation pathway of |
| GO:0006656 phosphatidylcholine biosynthetic process | IGI PMID:2445736 Yeast phosphatidylethanolamine methylation pathway. Cloning ... | ACCEPT | Summary: Both PEM1 (CHO2) and PEM2 (OPI3) are needed to maintain normal PC content. Supporting Evidence: PMID:2445736 Both genes were required for maintenance of the PC content of the yeast at a normal level. |
| GO:0006656 phosphatidylcholine biosynthetic process | IMP PMID:23000174 The membrane stress response buffers lethal effects of lipid... | ACCEPT | Summary: Thibault et al. 2012 used opi3 mutants (with ire1) showing PC depletion; choline rescues. Supporting Evidence: PMID:23000174 Indeed, cho2 and opi3 mutants displayed sharp declines of PC by thin layer chromatography PMID:23000174 Next, Opi3p methylates MMPE to N,N-dimethyl phosphatidylethanolamine (DMPE) in one step and to PC in the second |
| GO:0006656 phosphatidylcholine biosynthetic process | IMP PMID:6337128 Yeast mutant defective in phosphatidylcholine synthesis. | ACCEPT | Summary: opi3-3 mutant has 2-3% PC without choline and accumulates PMME and PDME. Supporting Evidence: PMID:6337128 The Saccharomyces cerevisiae opi3-3 mutant was shown to be defective in the synthesis of phosphatidylcholine via methylation of phosphatidylethanolamine. PMID:6337128 When grown in the absence of exogenous choline, the opi3-3 mutant had a phospholipid composition consisting of 2 to 3% phosphatidylcholine compared with 40 to 50% in wild-type strains. |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways superpathway RCA to phospholipid biosynthetic process. Correct general term. Supporting Evidence: PMID:6337128 The Saccharomyces cerevisiae opi3-3 mutant was shown to be defective in the synthesis of phosphatidylcholine via methylation of phosphatidylethanolamine. |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways superpathway RCA to phospholipid biosynthetic process. Correct general term. Supporting Evidence: PMID:6337128 The Saccharomyces cerevisiae opi3-3 mutant was shown to be defective in the synthesis of phosphatidylcholine via methylation of phosphatidylethanolamine. |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways superpathway RCA to phospholipid biosynthetic process. Correct general term. Supporting Evidence: PMID:6337128 The Saccharomyces cerevisiae opi3-3 mutant was shown to be defective in the synthesis of phosphatidylcholine via methylation of phosphatidylethanolamine. |
| GO:0008757 S-adenosylmethionine-dependent methyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro IPR024960 (PEMT/MFAP) to the generic SAM-dependent methyltransferase activity. True but uninformative. Reason: Specific phospholipid methyltransferase activity is established. Proposed replacements: phosphatidyl-N-methylethanolamine N-methyltransferase activity Supporting Evidence: PMID:2198947 phospholipid methyltransferase (PLMT) catalyzes the second two methylation reactions |
| GO:0031966 mitochondrial membrane | EXP PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | KEEP AS NON CORE | Summary: Mitochondrial proteome (Sickmann et al. 2003) used by SGD/UniProt for mitochondrial membrane. Abstract-only; probably ER-mitochondria contact association. Not the main site of activity. Reason: Defer to curator; secondary location. |
| GO:0031966 mitochondrial membrane | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: UniProt subcellular location (Mitochondrion membrane) mapping. Secondary location. Reason: Secondary location relative to ER. |
| GO:0071944 cell periphery | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | KEEP AS NON CORE | Summary: High-throughput GFP library signal at the cell periphery; plausibly cortical ER at ER-plasma membrane contacts. Reason: Secondary/peripheral location of an ER protein. |
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Download this section (compressed HTML)Methylene-fatty-acyl-phospholipid synthase; catalyzes the last two steps in phosphatidylcholine biosynthesis; also known as phospholipid methyltransferase
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