AstA (AruF, PA0896) is the alpha subunit of the arginine and ornithine N2-succinyltransferase of Pseudomonas aeruginosa, a heterotetramer of AruF and AruG subunits that catalyses the first step of the arginine succinyltransferase (AST) pathway, transferring the succinyl group of succinyl-CoA to L-arginine (and L-ornithine) to form N2-succinylarginine. The enzyme is allosteric towards ornithine and is inhibited by spermidine. The gene lies in the ArgR-controlled aruCFGDB operon, which is induced by arginine and enables aerobic use of arginine and ornithine as carbon and nitrogen sources. AstA has a GNAT-like acyl-CoA N-acyltransferase fold (Pfam AstA).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006527 L-arginine catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000764516 (PTHR30420, spanning AstA/AruG succinyltransferases and AstB dihydrolases), seeded by E. coli AstB and the three P. aeruginosa AST enzymes. Reason: Both subfamilies catalyse steps of the AST pathway, so the process term suits the node. Self-seed is expected; the IBD stands without it. Supporting Evidence: PMID:9393691 the aruF and aruG genes encode the subunits (AruAI and AruAII) of arginine and ornithine N2-succinyltransferases |
| GO:0006527 L-arginine catabolic process | IDA PMID:16593724 N-Succinylated intermediates in an arginine catabolic pathwa... | ACCEPT | Summary: PseudoCAP IDA and a seed of PTN000764516. The paper established the AST pathway, whose first step is the succinyltransferase reaction. Reason: Seed verdict SOUND. The term is correct for AstA; the gene assignment comes from PMID:7523119 and PMID:9393691. Abstract only. Supporting Evidence: PMID:16593724 Enzyme assays with crude P. aeruginosa extracts established the following pathway PMID:9393691 the aruF and aruG genes encode the subunits (AruAI and AruAII) of arginine and ornithine N2-succinyltransferases |
| GO:0006527 L-arginine catabolic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO from the AstA/AruG family signature; consistent. Reason: Consistent with the experimental and IBA rows on the same term. Supporting Evidence: file:PSEAE/astA/astA-uniprot.txt IPR007041; Arg_succinylTrfase_AstA/AruG |
| GO:0008791 L-arginine N-succinyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: L-arginine N-succinyltransferase activity is correct for the enzyme this chain belongs to; only the enables qualifier overstates single-chain autonomy. Reason: Correct and core. The purified Pseudomonas enzyme is a heterotetramer of two different chains (PMID:7523119), and astA/aruF encodes one of them (PMID:9393691), so the activity belongs to the complex: the term is right but contributes_to is the qualifier that scopes the claim correctly, and the core function below uses contributes_to. The qualifier error is recorded as a WRONG_QUALIFIER source defect, the same idiom as the E. coli NuoB/NuoC and CysI reviews. Supporting Evidence: PMID:7523119 After SDS/PAGE two subunits of 35 kDa and 37 kDa were evident, indicating that the enzyme is a heterotetramer. PMID:9393691 the aruF and aruG genes encode the subunits (AruAI and AruAII) of arginine and ornithine N2-succinyltransferases file:PSEAE/astA/astA-uniprot.txt SUBUNIT: Heterotetramer of two alpha and two beta subunits. |
| GO:0009015 N-succinylarginine dihydrolase activity | IBA GO_REF:0000033 | REMOVE | Summary: IBA from PTN000764516, seeded only by E. coli AstB (P76216), the dihydrolase. AstA is the succinyltransferase alpha subunit and has no dihydrolase activity. Reason: Wrong activity. PANTHER PTHR30420 groups two unrelated enzyme families: the AstB dihydrolases (SF2, Pfam AstB) and the AstA/AruG succinyltransferases (SF1, Pfam AstA, GNAT-like). The dihydrolase IBD was placed at PTN000764516, which spans both, so the step-2 activity is propagated to the step-1 enzyme. The leaf GAF shows the same IBA on all seven AstA-type leaves in the node. Node-level GO_CENTRAL defect recorded here (also applies to aruG). Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000764516 · PTN000764516 SOURCE BAD Root of PTHR30420, covering both SF1 (AstA/AruG succinyltransferases, 53 members) and SF2 (AstB dihydrolases, 138 members). GO:0009015 suits SF2 only. UniProtKB:P76216 · E. coli AstB (sole seed, IDA PMID:15703173) SUPPORTS SOURCE BUT NOT TARGET Valid dihydrolase evidence for AstB; does not transfer to AstA. Supporting Evidence: PMID:9393691 the aruF and aruG genes encode the subunits (AruAI and AruAII) of arginine and ornithine N2-succinyltransferases file:PSEAE/astA/astA-uniprot.txt PF04958; AstA |
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Download this section (compressed HTML)Q: What are the separate roles of the AruF and AruG subunits in catalysis and in the allosteric ornithine and spermidine regulation of the heterotetramer, given that E. coli has a single AstA?
Suggested experts: bacterial arginine catabolism
Q: Should PANTHER PTHR30420 be split, since it joins the unrelated AstA succinyltransferase and AstB dihydrolase families, and should the UniProt similarity note for AstA/AruG ("succinylarginine dihydrolase family") be revised?
Experiment: Express AruF and AruG separately and together and assay arginine and ornithine succinylation, to test whether either subunit alone is active.
Type: complex reconstitution and enzyme assay
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