gltA (P14165, PA1580) notes

Review session 2026-10-28 (PseudoCAP IBA-seed protocol, worklist rank 31)

No deep-research provider was available; the notes below are my own reading of the UniProt record, the
two cited papers (both abstract-only in the cache; the PubMed MCP returned no PMC full text for
PMC1135760 or PMC210395) and QuickGO.

Identity

• Pseudomonas aeruginosa PAO1 locus PA1580, UniProt P14165 (CISY_PSEAE, reviewed), 428 aa.
• Type I bacterial (hexameric, "large", NADH-sensitive) citrate synthase: InterPro IPR010953
  (Citrate_synthase_typ-I), IPR024176 (Citrate_synthase_bac-typ), NCBIfam TIGR01798 (cit_synth_I),
  Pfam PF00285, PROSITE PS00480; PANTHER PTHR42871:SF1. Active sites at 265, 306, 363 (UniProt FT ACT_SITE).
• UniProt: catalytic activity oxaloacetate + acetyl-CoA + H2O = citrate + CoA + H+ (EC 2.3.3.16, RHEA:16845),
  evidence ECO:0000269 PubMed:2507528; "Allosterically inhibited by NADH." (ECO:0000269 PubMed:2507528);
  subunit "Homohexamer."; pathway "tricarboxylic acid cycle; isocitrate from oxaloacetate: step 1/2."

Literature

• Donald et al. 1989 cloned and sequenced the gene and expressed it in E. coli
  PMID:2507528. The product, purified from the E. coli host, was active and
  NADH-inhibited PMID:2507528. Activity is therefore tied to this ORF
  PMID:2507528.
  Note that E. coli has its own gltA, so the activity assignment rests on separable peaks and the P.
  aeruginosa antiserum, not on a null background; UniProt and GOA nevertheless treat it as EXP and I agree.
• Mitchell et al. 1995 purified two citrate synthases from P. aeruginosa itself
  PMID:7626013; CSI is a hexamer PMID:7626013. CSI matches the gltA product (type I hexamer, NADH-regulated). The paper does not identify genes
  PMID:7626013, so the
  PseudoCAP attribution of the CSI activity to PA1580 is an inference from the type I hexamer, though a
  sound one. CSII (dimer, 36.5 kDa subunit) is probably the PrpC-type 2-methylcitrate synthase, which also
  has citrate synthase activity; I did not verify that.
• Process: citrate synthase catalyses the first step of the TCA cycle (UniProt PATHWAY line). Neither paper
  measures TCA cycle flux or a mutant phenotype; the PseudoCAP IDA to GO:0006099 is a process inferred from
  the activity (IC would be the accurate evidence code). The process claim itself is uncontroversial for
  the sole type I citrate synthase of PAO1.
• Citrate synthase also supplies citrate in the glyoxylate shunt; I do not propose a NEW glyoxylate cycle
  term because no P. aeruginosa gltA-specific evidence was read.

Annotation decisions

• GO:0036440 citrate synthase activity (EXP, IDA, IBA, IEA): ACCEPT, the core MF.
• GO:0006099 tricarboxylic acid cycle (IDA PseudoCAP, IBA, IEA): ACCEPT; evidence code of the PseudoCAP row
  flagged as SUSPECTED (IDA for a process inferred from enzyme activity).
• GO:0046912 acyltransferase activity, acyl groups converted into alkyl on transfer (IEA InterPro): MODIFY to
  GO:0036440, its descendant already carried.
• GO:0005829 cytosol (IBA, seeded by E. coli GltA P0ABH7 which has IDA/HDA cytosol): ACCEPT.
• GO:0005737 cytoplasm (IEA InterPro): MODIFY to cytosol (GO:0005829).

PseudoCAP IBA-seed assessment

QuickGO (2026-10-28, withFrom=PANTHER:PTN002450857) returns 54 IBA rows: 18 leaves each for GO:0036440,
GO:0006099 and GO:0005829 (cytosol is seeded by E. coli P0ABH7). The 18 leaves are type I citrate synthases:
gltA of E. coli (P0ABH7), Vibrio cholerae (Q9KQA8), Shewanella oneidensis (Q8EFP4), Xanthomonas (Q8P5V0),
Helicobacter pylori (P56062), and gltA proteins of Yersinia (taxon 632), Salmonella (99287), Coxiella
(227377), Bradyrhizobium (224911), Neisseria (122586), Rhodopirellula (243090) and Leptospira (189518, two),
Mycobacterium tuberculosis GltA2 (P9WPD5), Streptomyces CitA (Q9R339) and two Paramecium proteins (taxon
5888). E. coli GltA carries no experimental citrate synthase annotation in GOA, so P14165 is indeed the only
experimental seed.