SpeA (PA4839) is the biosynthetic arginine decarboxylase of Pseudomonas aeruginosa, a pyridoxal 5'-phosphate- and Mg2+-dependent enzyme of the Orn/Lys/Arg decarboxylase class-II family (SpeA subfamily). It decarboxylates L-arginine to agmatine, which agmatine deiminase (AguA) and N-carbamoylputrescine amidohydrolase (AguB) convert to putrescine. This arginine decarboxylase route and the ornithine decarboxylase (SpeC) route are redundant for putrescine synthesis; only a speA speC double mutant requires putrescine for growth.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: Root MF term from InterPro2GO. Reason: Entailed by GO:0008792 arginine decarboxylase activity, accepted below. |
| GO:0006527 L-arginine catabolic process | IEA GO_REF:0000002 | UNDECIDED | Summary: InterPro2GO from the arginine decarboxylase signature. P. aeruginosa does degrade arginine through an arginine decarboxylase (agmatine) pathway, but the literature I could read does not show whether the biosynthetic SpeA is the decarboxylase used for catabolism. Reason: The only documented role of SpeA is putrescine biosynthesis. A catabolic role is plausible but not established from the abstracts available. |
| GO:0008295 spermidine biosynthetic process | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: Combined IEA from the SpeA UniRule and InterPro signature. Reason: Agmatine made by SpeA is converted to putrescine, the precursor of spermidine, so SpeA contributes an upstream step; its direct product feeds putrescine synthesis, the core process. |
| GO:0008792 arginine decarboxylase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN008680444, seeded by E. coli SpeA (several IDA/EXP rows), two Arabidopsis ADCs and the IMP on Q9HUX1 itself (expected, not circular). The IBD stands without this seed. Reason: Core activity of a SpeA-subfamily ADC. Supporting Evidence: PMID:12634339 The activities of the two decarboxylases were similar and each enzyme alone appeared to direct sufficient formation of the polyamine for normal growth. |
| GO:0008792 arginine decarboxylase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA for ADC activity. Reason: Agrees with the experimental and phylogenetic rows. |
| GO:0008792 arginine decarboxylase activity | IMP PMID:12634339 Identification of the putrescine biosynthetic genes in Pseud... | ACCEPT | Summary: PseudoCAP (and CACAO) seed row. The abstract identifies speA as the ADC gene, reports ADC activity comparable to ODC, and shows putrescine auxotrophy of the speA speC double mutant. Reason: Seed verdict SOUND. Supporting Evidence: PMID:12634339 A mutant defective in both speA and speC was a putrescine auxotroph. |
| GO:0009446 putrescine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN008680444, seeded by E. coli SpeA and Arabidopsis ADC2. Reason: ADC catalyses the first step of the agmatine route to putrescine, and the speA speC double-mutant auxotrophy confirms the role in P. aeruginosa. The more specific "from arginine, via agmatine" term is obsolete. Supporting Evidence: PMID:12634339 A mutant defective in both speA and speC was a putrescine auxotroph. |
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Download this section (compressed HTML)Q: Does SpeA also supply agmatine for the catabolic arginine decarboxylase pathway when arginine is the carbon and nitrogen source, or is a separate catabolic decarboxylase involved?
Experiment: Compare growth on L-arginine as sole carbon source and agmatine formation in speA mutants built in arginine succinyltransferase (aru) and arginine deiminase (arc) pathway-defective backgrounds, to test whether SpeA is the catabolic arginine decarboxylase.
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