Ppc (PP_1505) is the type-1 phosphoenolpyruvate carboxylase of Pseudomonas putida KT2440, a soluble enzyme that carboxylates phosphoenolpyruvate with bicarbonate to form oxaloacetate and phosphate. It acts as an anaplerotic enzyme at the phosphoenolpyruvate-pyruvate-oxaloacetate node, replenishing oxaloacetate for the tricarboxylic acid cycle and for biosynthesis, alongside the two-subunit pyruvate carboxylase PycAB. Bacterial type-1 PEPCs such as the characterised Escherichia coli enzyme are allosterically activated by acetyl-CoA and fructose 1,6-bisphosphate and inhibited by aspartate and malate; this regulation has not been tested in KT2440.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000287 magnesium ion binding | IEA GO_REF:0000104 | KEEP AS NON CORE | Summary: Mg2+ cofactor of PEPC. Reason: Metal binding is a cofactor property of the PEP carboxylase activity. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt DR HAMAP; MF_00595; PEPcase_type1; 1. |
| GO:0005829 cytosol | IEA GO_REF:0000118 | ACCEPT | Summary: Soluble cytosolic enzyme (TreeGrafter). Reason: Bacterial type-1 PEPCs are soluble cytosolic enzymes, as shown for the E. coli orthologue. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt DR HAMAP; MF_00595; PEPcase_type1; 1. |
| GO:0006099 tricarboxylic acid cycle | IEA GO_REF:0000002 | REMOVE | Summary: Ppc feeds the TCA cycle but catalyses none of its steps. Reason: The InterPro2GO mapping places PEP carboxylase in the TCA cycle, but Ppc replenishes oxaloacetate from PEP (anaplerosis) and catalyses no step of the cycle; the same row is removed on E. coli Ppc. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt Forms oxaloacetate, a four-carbon dicarboxylic acid source for the tricarboxylic acid cycle. |
| GO:0006107 oxaloacetate metabolic process | IEA GO_REF:0000104 | ACCEPT | Summary: Ppc forms oxaloacetate from PEP, its anaplerotic role. Reason: Oxaloacetate formation is the direct product of the Ppc reaction; GO has no more specific anaplerotic term. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt Forms oxaloacetate, a four-carbon dicarboxylic acid source for the tricarboxylic acid cycle. |
| GO:0008964 phosphoenolpyruvate carboxylase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Exact PEP carboxylase activity. Reason: Q88MR4 matches the HAMAP PEPCase type-1 rule and carries both PEPC active-site signatures. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt DR HAMAP; MF_00595; PEPcase_type1; 1. file:PSEPK/ppc/ppc-uniprot.txt DR PROSITE; PS00393; PEPCASE_2; 1. file:PSEPK/ppc/ppc-deep-research-falcon.md **ppc is explicitly listed as “Phosphoenolpyruvate carboxylase” with locus tag PP1505** |
| GO:0015977 carbon fixation | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: Bicarbonate incorporation by heterotrophic Ppc is anaplerosis, not carbon fixation. Reason: The carbon fixation term reflects photosynthetic plant PEPC roles transferred by the family rule; in heterotrophic KT2440 Ppc replenishes TCA intermediates. Same verdict as E. coli Ppc. Supporting Evidence: file:PSEPK/ppc/ppc-uniprot.txt Forms oxaloacetate, a four-carbon dicarboxylic acid source for the tricarboxylic acid cycle. |
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Download this section (compressed HTML)Q: Is KT2440 Ppc subject to the same acetyl-CoA and FBP activation as E. coli Ppc, given that KT2440 lacks a functional EMP route and may hold low FBP?
Experiment: Purify PP_1505 and measure PEP carboxylase kinetics with acetyl-CoA, FBP, aspartate and malate.
Type: enzyme kinetics
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Download this section (compressed HTML)Curated by Claude (AI-assisted). Rows that quoted DR GO lines or ARBA-only text were
re-supported with family/domain classification (NCBIfam, PIRSF, HAMAP, PROSITE, InterPro) and,
where useful, orthologue literature. Correct-but-general parent terms are MODIFY to the specific
activity already on the gene. Verdicts were aligned with the experimentally anchored E. coli
(aceE, aceF, ppc, pykF, ppsA) and B. subtilis (pycA) reviews. The KT2440 PDH/OGDH E3 is LpdG
(PP_4187), not Lpd (PP_5366, LPD-3). No KT2440-specific enzymology was found for this gene.
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