SpuI (PA0296, PauA1) is a glutamine synthetase-like gamma-glutamylpolyamine synthetase of Pseudomonas aeruginosa PAO1, homologous to Escherichia coli PuuA, which gamma-glutamylates putrescine as the first step of the gamma-glutamylation route from polyamines to GABA. spuI is transcribed divergently from the polyamine-inducible spuABCDEFGH operon. A spuI single mutant grows normally on polyamines, but spuI is needed together with its paralogs pauA4 (and pauA2) for growth on putrescine and with pauA4 and pauA5 for growth on cadaverine, so it is a redundant diamine-glutamylating enzyme of polyamine catabolism. Its activity has not been assayed with purified protein.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO from the GS/guanido kinase catalytic domain. Reason: Entailed by GO:0016880 acid-ammonia (or amide) ligase activity, the core function MF. |
| GO:0004356 glutamine synthetase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from GS domain signatures, which do not separate glutamine synthetases from gamma-glutamylpolyamine synthetases. Reason: Reaction class right, substrate wrong. SpuI/PauA1 is a PuuA-family enzyme acting in putrescine and cadaverine catabolism; GlnA is the P. aeruginosa glutamine synthetase. Glutamate-putrescine ligase (GO:0034024) is likely but unassayed and SpuI may also take cadaverine, so generalize to the parent class. Proposed replacements: acid-ammonia (or amide) ligase activity Supporting Evidence: file:PSEAE/spuI/spuI-uniprot.txt PANTHER; PTHR43785; GAMMA-GLUTAMYLPUTRESCINE SYNTHETASE; 1. |
| GO:0006598 polyamine catabolic process | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA from PTN001839150 seeded by E. coli PuuA, PA1566/PauA3, SpuB/PauA2 and SpuI itself. SpuI's own seed rows are mis-referenced, but the IBD stands on PuuA (IMP and IDA), PauA3 and PauA2, and the term is true for SpuI. Reason: Entailed by GO:0009447 putrescine catabolic process (is_a GO:0006598), accepted below. |
| GO:0009447 putrescine catabolic process | IMP PMID:12081945 Functional analysis and regulation of the divergent spuABCDE... | ACCEPT | Summary: PseudoCAP seed row. The cited paper states that spuI mutations caused no growth defect on polyamines, so it does not support the row. The term is nonetheless true for SpuI/PauA1 from PMID:21622750 (pauA1A4 and pauA1A2A4 mutants fail to grow on putrescine). Seed verdict WRONG (reference). Reason: The claim holds on other evidence, so the row is kept, but its reference should be re-pointed. PauA1 is a predicted putrescine-glutamylating enzyme, the first step of the pathway, so it does work in the process. Supporting Evidence: PMID:21622750 The results revealed that it requires specific combinations of pauA knockouts to abolish utilization of different polyamines |
| GO:0016879 ligase activity, forming carbon-nitrogen bonds | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA ligase (C-N) activity. Reason: Entailed by GO:0016880 (is_a GO:0016879), the core function MF. |
| GO:0042402 biogenic amine catabolic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA biogenic amine catabolism. Reason: Entailed by GO:0009447 putrescine catabolic process, accepted above. |
| GO:0046203 spermidine catabolic process | IMP PMID:12081945 Functional analysis and regulation of the divergent spuABCDE... | REMOVE | Summary: PseudoCAP seed row. The cited paper reports no growth defect of spuI mutants on polyamines, and the later pauA analysis assigns spermidine utilization to pauA2 (spuB), not pauA1. Seed verdict WRONG. Reason: No evidence places SpuI in spermidine catabolism. The cited paper reports the opposite phenotype (normal growth), and in PMID:21622750 the pauA1 single mutant grows on spermidine while a pauA2 single knockout alone blocks it. Supporting Evidence: PMID:12081945 While mutations on spuI did not show any growth defect on agmatine and polyamines |
| GO:1901704 L-glutamine biosynthetic process | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA from the deep GS-family node PTN000464978 (seed B. subtilis GlnA). SpuI sits in the PuuA-like gamma-glutamylpolyamine synthetase clade. Reason: Over-propagation of the ancestral glutamine synthetase role to a substrate-diverged paralog that acts in putrescine catabolism; GlnA supplies glutamine in P. aeruginosa. Not REMOVE because residual glutamine synthesis has not been tested. Propagation Review Root cause: PROPAGATION BAD Failure modes: FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN000464978 · PTN000464978 SUPPORTS SOURCE BUT NOT TARGET GS-family node; right for GlnA, not for the PuuA/PauA subclade. UniProtKB:P12425 · B. subtilis GlnA SUPPORTS SOURCE BUT NOT TARGET Bona fide glutamine synthetase. Supporting Evidence: file:PSEAE/spuI/spuI-uniprot.txt PANTHER; PTHR43785; GAMMA-GLUTAMYLPUTRESCINE SYNTHETASE; 1. |
| GO:1901704 L-glutamine biosynthetic process | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: InterPro2GO from GS N-terminal domain signatures. Reason: Same claim and reasoning as the IBA row. |
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Download this section (compressed HTML)Q: What are the relative putrescine and cadaverine specificities of PauA1 versus PauA4 and PauA5, which explain the combinations of knockouts needed to block growth on each diamine?
Experiment: Assay purified SpuI/PauA1 for ATP-dependent gamma-glutamylation of putrescine, cadaverine, 1,3-diaminopropane and spermidine, and for glutamine synthetase activity with ammonia.
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