psd1 encodes the mitochondrial phosphatidylserine decarboxylase of Schizosaccharomyces pombe (EC 4.1.1.65), a member of the PISD/Psd1 family. Like other PSDs, it is made as a proenzyme that self-cleaves into beta and pyruvoyl-containing alpha chains, and it decarboxylates phosphatidylserine to phosphatidylethanolamine. It has a predicted mitochondrial targeting sequence and transmembrane segment, localizes to mitochondria (without the ER pool seen for S. cerevisiae Psd1), and is the PSD needed for respiratory growth. psd1, psd2 and psd3 overlap: only the triple deletion lowers PE enough to need ethanolamine, and lack of PE causes defects in morphology and cytokinesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004609 phosphatidylserine decarboxylase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA from PTN000007430 (PSD1-type node with S. cerevisiae Psd1, human PISD, E. coli Psd, and S. pombe psd1 and psd2). Reason: Phylogenetic inference consistent with S. pombe genetic data. Supporting Evidence: PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0004609 phosphatidylserine decarboxylase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from InterPro PSD signatures, HAMAP UniRule UR000370960, RHEA:20828 and EC 4.1.1.65. Reason: Correct family mapping; psd1 retains the PSD domain with the autocatalytic serine. Supporting Evidence: file:SCHPO/psd1/psd1-uniprot.txt Reaction=a 1,2-diacyl-sn-glycero-3-phospho-L-serine + H(+) = a 1,2- |
| GO:0004609 phosphatidylserine decarboxylase activity | IGI PMID:19286980 Phosphatidylethanolamine is required for normal cell morphol... | ACCEPT | Summary: Luo et al. (2009): the psd1 psd2 psd3 triple deletion has reduced PE and requires ethanolamine, while single and double deletions grow; with/from psd2 and psd3. Reason: Genetic redundancy evidence for PSD function; no direct enzyme assay of psd1 alone, but the activity is well supported by family membership. Deferring to the curator. Supporting Evidence: PMID:19286980 mutants carrying deletions in all three psd genes (psd1-3Delta mutants) grow slowly in rich medium and are inviable in minimal medium, indicating that the psd1 to psd3 gene products share overlapping essential cellular functions PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0004609 phosphatidylserine decarboxylase activity | IMP PMID:19286980 Phosphatidylethanolamine is required for normal cell morphol... | ACCEPT | Summary: Same study; the triple deletion lowers PE. Reason: As above; core activity. Supporting Evidence: PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0005739 mitochondrion | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: ORFeome YFP localization found Psd1 in mitochondria, as summarized by Luo et al. Reason: Consistent with mNG-tagging in PMID:34818062. Supporting Evidence: PMID:19286980 found that Psd1 is localized to mitochondria and that Psd2 is localized both to mitochondria and to the nuclear envelope |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA (PTN000007431) to mitochondrion from PSD1-type orthologs. Reason: Correct. Supporting Evidence: PMID:34818062 Consistent with predicted targeting to the IMM, SpPsd1-mNG localized to mitochondria |
| GO:0005739 mitochondrion | IDA PMID:34818062 ER-localized phosphatidylethanolamine synthase plays a conse... | ACCEPT | Summary: Gok et al. (2022) chromosomally tagged Psd1 with mNeonGreen and found it colocalized with mito-mCherry; unlike S. cerevisiae Psd1, no ER pool was detected. Reason: Direct S. pombe evidence. Supporting Evidence: PMID:34818062 Consistent with predicted targeting to the IMM, SpPsd1-mNG localized to mitochondria PMID:34818062 we did not detect obvious ER targeting of SpPsd1 |
| GO:0005739 mitochondrion | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from InterPro IPR033661 and UniProt SubCell SL-0173 (mitochondrion). Reason: Correct. Supporting Evidence: PMID:34818062 Consistent with predicted targeting to the IMM, SpPsd1-mNG localized to mitochondria |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt SubCell SL-0168 and HAMAP UniRule UR000370960 (single-pass inner membrane, intermembrane side). Reason: Psd1 has a predicted mitochondrial targeting sequence and transmembrane domain like PISD isoform 1; inner membrane is the expected site. Supporting Evidence: file:SCHPO/psd1/psd1-uniprot.txt Mitochondrion inner membrane PMID:34818062 contains a computationally predicted MTS and TMD akin to isoform 1 of human PISD |
| GO:0005743 mitochondrial inner membrane | ISS GO_REF:0000024 | ACCEPT | Summary: Curator transfer from S. cerevisiae Psd1 (P39006), an inner-membrane enzyme. Reason: Core location; used in the PomBase GO-CAM 6796b94c00000009. Supporting Evidence: PMID:34818062 contains a computationally predicted MTS and TMD akin to isoform 1 of human PISD |
| GO:0006646 phosphatidylethanolamine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA (PTN000007430) to PE biosynthetic process. Reason: Core process. Supporting Evidence: PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0006646 phosphatidylethanolamine biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: HAMAP UniRule and UniPathway UPA00558 (PE from CDP-DAG, step 2/2). Reason: Correct. Supporting Evidence: file:SCHPO/psd1/psd1-uniprot.txt Reaction=a 1,2-diacyl-sn-glycero-3-phospho-L-serine + H(+) = a 1,2- |
| GO:0006646 phosphatidylethanolamine biosynthetic process | IGI PMID:19286980 Phosphatidylethanolamine is required for normal cell morphol... | ACCEPT | Summary: psd1-3 triple deletion reduces PE; with/from psd2 and psd3. Reason: Core process; S. pombe genetic evidence. Supporting Evidence: PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0006646 phosphatidylethanolamine biosynthetic process | IMP PMID:19286980 Phosphatidylethanolamine is required for normal cell morphol... | ACCEPT | Summary: Same triple-deletion PE measurements. Reason: Core process. Supporting Evidence: PMID:19286980 psd1-3Delta cells produce lower levels of phosphatidylethanolamine than wild-type cells, even in medium supplemented with ethanolamine |
| GO:0006656 phosphatidylcholine biosynthetic process | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Curator transfer from S. cerevisiae Psd1 to PC biosynthetic process, since PE made by Psd1 is methylated to PC by cho2 and cho1. Reason: Correct upstream step of de novo PC synthesis, but the direct product is PE; matches the S. cerevisiae PSD1 review. |
| GO:0008654 phospholipid biosynthetic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro PSD signatures mapped to phospholipid biosynthetic process. Reason: Correct but generic parent of PE biosynthesis. |
| GO:0016540 protein autoprocessing | IEA GO_REF:0000104 | ACCEPT | Summary: HAMAP UniRule UR000370960: PSD proenzymes self-cleave to generate the pyruvoyl cofactor. Reason: Autocatalytic maturation is intrinsic to PSD enzymes and is done by the protein itself; accepted as in the S. cerevisiae PSD1 review. Supporting Evidence: file:SCHPO/psd1/psd1-uniprot.txt Is synthesized initially as an inactive proenzyme |
| GO:0046474 glycerophospholipid biosynthetic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA00028351 mapping to glycerophospholipid biosynthetic process. Reason: Correct but generic. |
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Experiment: Measure PSD activity in isolated mitochondria from psd1, psd2 and psd1 psd2 deletion strains to apportion mitochondrial PE synthesis between the two enzymes.
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