gltA (PA1580) encodes the type I ("large", hexameric) citrate synthase of Pseudomonas aeruginosa, a soluble cytoplasmic enzyme that condenses acetyl-CoA with oxaloacetate to form citrate and CoA (EC 2.3.3.16), the first and committing step of the tricarboxylic acid cycle. Like other Gram-negative type I citrate synthases it is a homohexamer that is allosterically inhibited by NADH, which couples entry of carbon into the cycle to the cellular redox state. The gene was cloned and expressed in Escherichia coli, and the native hexameric enzyme (CSI) was purified from P. aeruginosa alongside a distinct dimeric isoenzyme (CSII) encoded by a different gene.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005737 cytoplasm | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from the type I citrate synthase signature. Correct for a soluble TCA cycle enzyme without signal peptide or transmembrane segments, but less specific than cytosol. Reason: The location is right but general. The gene already carries cytosol (GO:0005829) by IBA from a node whose location seed, E. coli GltA, has direct cytosol evidence, so the row is refined to that descendant. Proposed replacements: cytosol Supporting Evidence: file:PSEAE/gltA/gltA-uniprot.txt Citrate_synthase_typ-I |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002450857, seeded for location by E. coli GltA (P0ABH7), which has IDA and HDA cytosol annotations. P. aeruginosa GltA is a close ortholog (70% identity) of the same soluble type I enzyme. Reason: Type I citrate synthases are soluble cytoplasmic enzymes; the target is inside the clade, has no membrane-targeting features, and there is no evidence of divergence. The node placement is sound. Supporting Evidence: PMID:2507528 the inferred amino acid sequence was 70 and 76% identical, respectively, with the citrate synthase sequences from E. coli and Acinetobacter anitratum |
| GO:0006099 tricarboxylic acid cycle | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002450857, whose sole seed is this gene's PseudoCAP IDA (PMID:7626013). The target appearing in its own WITH/FROM is expected. Reason: Citrate synthase catalyses the first step of the TCA cycle, and the node is a clade of type I housekeeping citrate synthases (18 leaves in 16 taxa, including E. coli, Vibrio and Salmonella GltA), so the process suits every leaf. The seed's evidence code is generous (activity, not process, was measured), but the IBD conclusion is correct. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002450857 · PTN002450857 SUPPORTS TRANSFER QuickGO (2026-10-28) lists 18 leaves per term, all type I citrate synthases (gltA of Proteobacteria, Leptospira, Rhodopirellula, M. tuberculosis GltA2, Streptomyces CitA, two Paramecium proteins). UniProtKB:P14165 · gltA SUPPORTS TRANSFER The target's own experimental annotation is the IBD seed; expected, not circular. Supporting Evidence: file:PSEAE/gltA/gltA-uniprot.txt Carbohydrate metabolism; tricarboxylic acid cycle; isocitrate from oxaloacetate |
| GO:0006099 tricarboxylic acid cycle | IDA PMID:7626013 Purification and characterization of citrate synthase isoenz... | ACCEPT | Summary: PseudoCAP IDA from the purification and characterisation of the P. aeruginosa citrate synthase isoenzymes. The paper assays the enzyme; it does not measure TCA cycle participation. This row is the sole seed of the TCA cycle IBD at PTN002450857. Reason: The process claim is correct, since citrate synthase activity is by definition the TCA cycle's entry step and gltA is the only type I citrate synthase of PAO1. The evidence code overstates the paper, which shows activity of the purified native CSI hexamer rather than a process; IC from the activity would be accurate. That is recorded as a suspected evidence-code defect, not a reason to reject the claim. Supporting Evidence: PMID:7626013 Two types of citrate synthase (CS) have been purified from Pseudomonas aeruginosa, a 'large' form (CSI) and a 'small' form (CSII). |
| GO:0006099 tricarboxylic acid cycle | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation from the bacterial-type citrate synthase signature and the UniPathway TCA cycle assignment. Agrees with the IBA and PseudoCAP rows. Reason: Consistent with the curated UniProt pathway line and the enzyme's activity. Supporting Evidence: file:PSEAE/gltA/gltA-uniprot.txt Carbohydrate metabolism; tricarboxylic acid cycle; isocitrate from oxaloacetate |
| GO:0036440 citrate synthase activity | EXP PMID:2507528 Cloning, sequencing, and expression of the gene for NADH-sen... | ACCEPT | Summary: UniProt EXP from the cloning and expression of the P. aeruginosa gene in E. coli; the expressed product was purified as active, NADH-inhibited citrate synthase. Reason: Direct assay of the cloned gene product; this is the core molecular function. Supporting Evidence: PMID:2507528 the proteins were identical by immunological criteria and very similar in kinetics of substrate saturation and NADH inhibition file:PSEAE/gltA/gltA-uniprot.txt Reaction=oxaloacetate + acetyl-CoA + H2O = citrate + CoA + H(+); |
| GO:0036440 citrate synthase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN002450857, whose sole experimental seed is this gene (UniProt EXP PMID:2507528 and PseudoCAP IDA PMID:7626013). Reason: The seed is direct biochemistry, the catalytic residues and the PROSITE citrate synthase signature are conserved across the clade, and every leaf is a canonical type I citrate synthase. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN002450857 · PTN002450857 SUPPORTS TRANSFER Clade of 18 type I citrate synthases (QuickGO 2026-10-28). UniProtKB:P14165 · gltA SUPPORTS TRANSFER The target's own experimental annotations are the IBD seed; expected, not circular. Supporting Evidence: PMID:2507528 the proteins were identical by immunological criteria and very similar in kinetics of substrate saturation and NADH inhibition |
| GO:0036440 citrate synthase activity | IDA PMID:7626013 Purification and characterization of citrate synthase isoenz... | ACCEPT | Summary: PseudoCAP IDA from the purified native 'large' citrate synthase (CSI) of P. aeruginosa, a hexamer, which corresponds to the gltA product. Co-seed of the citrate synthase activity IBD. Reason: The paper does not name the gene, but CSI is the hexameric, regulated type I enzyme, matching the homohexameric NADH-inhibited GltA characterised from the cloned gene (PMID:2507528); CSII is a distinct dimeric isoenzyme from another gene. The attribution is sound and the activity is directly assayed. Supporting Evidence: PMID:7626013 Chemical cross-linking of the native enzymes with either dimethyl suberimidate or glutaraldehyde followed by electrophoretic analysis by SDS/PAGE showed that CSI is a hexamer and CSII is a dimer. |
| GO:0036440 citrate synthase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic mapping from the curated EC 2.3.3.16 / RHEA:16845 reaction, itself based on experimental evidence (ECO:0000269, PubMed:2507528). Reason: Matches the experimental annotations. Supporting Evidence: file:PSEAE/gltA/gltA-uniprot.txt Reaction=oxaloacetate + acetyl-CoA + H2O = citrate + CoA + H(+); |
| GO:0046912 acyltransferase activity, acyl groups converted into alkyl on transfer | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from citrate synthase family signatures to the generic parent class. Reason: True but general; citrate synthase activity (GO:0036440), which the gene carries by EXP and IDA, is the specific descendant. Proposed replacements: citrate synthase activity Supporting Evidence: file:PSEAE/gltA/gltA-uniprot.txt Belongs to the citrate synthase family. |
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Download this section (compressed HTML)Q: Is the dimeric CSII isoenzyme purified by Mitchell et al. the PrpC-type 2-methylcitrate synthase (PA0795), and does it contribute citrate synthase activity in vivo when gltA is absent?
Experiment: Compare growth of a PA1580 deletion and a PA1580 PA0795 double mutant on acetate, glucose and glutamate, and measure citrate synthase activity in their extracts, to establish whether GltA is the sole TCA cycle citrate synthase.
Type: genetic knockout with metabolic phenotyping
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