Phosphate acetyltransferase Pta (PP_0774) is a cytoplasmic enzyme of Pseudomonas putida KT2440 that catalyzes reversible acetyl transfer between acetyl-CoA and inorganic phosphate, producing acetyl phosphate and free CoA in the forward direction. Pta activity is detected in cell-free extracts and depends on an intact pta gene. The 695-residue protein contains an N-terminal CobB/CobQ-like region and a C-terminal phosphate acetyltransferase region. Native Pta can supply acetyl phosphate to an introduced Escherichia coli acetate kinase for ATP and acetate production, but this engineered coupling does not establish a complete native AckA–Pta pathway or the physiological importance of reverse acetyl-CoA synthesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasmic localization for a soluble central-metabolism enzyme acting on acetyl-CoA, acetyl phosphate, and inorganic phosphate. Reason: Cytoplasmic localization is the curated UniProt assignment and is consistent with the soluble metabolic activity measured in cell-free extracts. The primary study does not directly localize Pta; the location is retained as a supported inference rather than a compartment-resolved experimental result. Supporting Evidence: file:PSEPK/pta/pta-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm |
| GO:0008959 phosphate acetyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Precise molecular function term matching EC 2.3.1.8 and RHEA:19521 (acetyl-CoA + phosphate = acetyl phosphate + CoA); this is the core catalytic activity of Pta. Reason: The frozen curated reaction matches EC2.3.1.8 and RHEA:19521. Independently checked full-text PMID23149123 reports phosphotransacetylase activity in KT2440 extracts and its loss in the pta::mini-Tn5 mutant (PP0774). The engineered strain couples this native activity to introduced E. coli AckA; this is direct support for Pta chemistry, not proof of an intact native AckA–Pta pathway. Supporting Evidence: file:PSEPK/pta/pta-uniprot.txt Reaction=acetyl-CoA + phosphate = acetyl phosphate + CoA; file:PSEPK/pta/pta-source-analysis/PMID23149123-scoped-evidence.md we did not detect any significant activity, suggesting that the enzymatic activity was dependent on an intact pta gene. |
| GO:0016407 acetyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad acetyltransferase activity claim is correct and can be refined to phosphate acetyltransferase activity. Reason: GO:0008959 is a verified descendant of this term and is already annotated to this protein. The frozen curated UniProt reaction and direct KT2440 WT-versus-pta::mini-Tn5 extract assays support that precise activity. Generality or overlap does not make the broad acyl-transfer claim an over-annotation; this is a specificity refinement, not rejection of InterPro or PTHR43356 family biology. Proposed replacements: phosphate acetyltransferase activity Supporting Evidence: file:PSEPK/pta/pta-uniprot.txt Reaction=acetyl-CoA + phosphate = acetyl phosphate + CoA; file:PSEPK/pta/pta-source-analysis/PMID23149123-scoped-evidence.md we did not detect any significant activity, suggesting that the enzymatic activity was dependent on an intact pta gene. |
| GO:0016746 acyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad acyltransferase activity claim is correct and can be refined to phosphate acetyltransferase activity. Reason: GO:0008959 is a verified descendant of this term and is already annotated to this protein. The frozen curated UniProt reaction and direct KT2440 WT-versus-pta::mini-Tn5 extract assays support that precise activity. Generality or overlap does not make the broad acyl-transfer claim an over-annotation; this is a specificity refinement, not rejection of InterPro or PTHR43356 family biology. Proposed replacements: phosphate acetyltransferase activity Supporting Evidence: file:PSEPK/pta/pta-uniprot.txt Reaction=acetyl-CoA + phosphate = acetyl phosphate + CoA; file:PSEPK/pta/pta-source-analysis/PMID23149123-scoped-evidence.md we did not detect any significant activity, suggesting that the enzymatic activity was dependent on an intact pta gene. |
| GO:0006085 acetyl-CoA biosynthetic process | IEA GO_REF:0000041 | UNDECIDED | Summary: Native acetyl-CoA biosynthesis through Pta is unresolved despite its reversible molecular activity. Reason: The UniPathway mapping assigns the reverse acetate-assimilation route, but reaction reversibility alone does not establish a native process. PMID23149123 verifies Pta activity while reporting that KT2440 lacks acetate kinase and that native Pta physiological relevance remains uncertain. Its demonstrated energy-coupling experiment introduces E. coli AckA and consumes acetyl-CoA. Other acetyl-phosphate sources or physiological reverse flux are not excluded, so the native biosynthetic-process claim is unresolved rather than disproven. Do not infer a native pathway merely from the engineered strain or a pathway diagram. Supporting Evidence: file:PSEPK/pta/pta-source-analysis/PMID23149123-scoped-evidence.md P. putida KT2440 only encodes a pta (PP0774, annotated as phosphate acetyltransferase; Fig. 2A) and completely lacks an acetate kinase gene. file:PSEPK/pta/pta-source-analysis/PMID23149123-scoped-evidence.md These results suggest that Pta is indeed active in P. putida KT2440 in a growth-phase dependent fashion, but its relevance (if any) on the cell physiology remains uncertain. file:PSEPK/pta/pta-uniprot.txt Reaction=acetyl-CoA + phosphate = acetyl phosphate + CoA; |
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