SpeC (PA4519) is the biosynthetic ornithine decarboxylase of Pseudomonas aeruginosa, a pyridoxal 5'-phosphate-dependent fold-type III decarboxylase of the eukaryote-like ODC family (Orn/Lys/Arg decarboxylase class II). It decarboxylates L-ornithine to putrescine, the direct route of putrescine synthesis. P. aeruginosa also makes putrescine from arginine through arginine decarboxylase (SpeA) followed by agmatine deiminase (AguA) and N-carbamoylputrescine amidohydrolase (AguB). The ODC and ADC activities are similar in size and either route alone supports normal growth, so only a speA speC double mutant (or an aguAB speC mutant) requires putrescine.
| 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:0004586 ornithine decarboxylase activity, accepted below. Supporting Evidence: file:PSEAE/speC/speC-uniprot.txt DR InterPro; IPR002433; Orn_de-COase. |
| GO:0004586 ornithine decarboxylase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000159726, seeded by human, mouse, rat, yeast, Candida, Plasmodium and C. elegans ODCs plus the PseudoCAP IMP on Q9HVQ3 itself (expected, not circular). Correct for speC; the IBD stands without this seed. A node-level problem elsewhere in the clade (AZIN1) is recorded as a GO_CENTRAL defect. Reason: Core activity of a fold-type III ODC, supported by genetics in P. aeruginosa and by many seeds. 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. PMID:12634339 Putrescine can be synthesized either directly from ornithine by ornithine decarboxylase (ODC; the speC product) or indirectly from arginine via arginine decarboxylase (ADC; the speA product). file:PSEAE/speC/speC-uniprot.txt DR InterPro; IPR002433; Orn_de-COase. |
| GO:0004586 ornithine decarboxylase activity | IMP PMID:12634339 Identification of the putrescine biosynthetic genes in Pseud... | ACCEPT | Summary: PseudoCAP seed row. The abstract identifies speC as the ODC gene, reports ODC activity comparable to ADC, and shows putrescine auxotrophy of the speA speC double mutant. Reason: Seed verdict SOUND. Nakada and Itoh identified speC as the ODC gene of PAO1, measured ODC activity comparable to ADC, and showed that loss of speC together with speA causes putrescine auxotrophy. The cached record is abstract-only; the PseudoCAP curator's reading of the mutant data is deferred to. Supporting Evidence: PMID:12634339 A mutant defective in both speA and speC was a putrescine auxotroph. PMID:12634339 Putrescine can be synthesized either directly from ornithine by ornithine decarboxylase (ODC; the speC product) or indirectly from arginine via arginine decarboxylase (ADC; the speA product). 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:0005737 cytoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000159726; SpeC has no signal peptide or TM segment and acts in the cytoplasm. Reason: Correct location for a soluble biosynthetic decarboxylase. The record has no signal peptide or transmembrane feature and the substrates and PLP cofactor are cytoplasmic; no localization assay exists for this protein. Supporting Evidence: file:PSEAE/speC/speC-uniprot.txt DR InterPro; IPR002433; Orn_de-COase. file:PSEAE/speC/speC-uniprot.txt DR CDD; cd00622; PLPDE_III_ODC; 1. |
| GO:0006596 polyamine biosynthetic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro2GO from the ODC signature. Reason: Entailed by GO:0009446 putrescine biosynthetic process (is_a), accepted below. Supporting Evidence: PMID:12634339 A mutant defective in both speA and speC was a putrescine auxotroph. file:PSEAE/speC/speC-uniprot.txt DR InterPro; IPR002433; Orn_de-COase. |
| GO:0009446 putrescine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN000159726, eukaryotic ODC seeds. Reason: ODC catalyses putrescine formation from ornithine; the P. aeruginosa double-mutant auxotrophy confirms the pathway role. Supporting Evidence: PMID:12634339 A mutant defective in both speA and speC was a putrescine auxotroph. PMID:12634339 Putrescine can be synthesized either directly from ornithine by ornithine decarboxylase (ODC; the speC product) or indirectly from arginine via arginine decarboxylase (ADC; the speA product). |
| GO:0016831 carboxy-lyase activity | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA generic term. Reason: Entailed by GO:0004586 (is_a GO:0016831), accepted above. Supporting Evidence: file:PSEAE/speC/speC-uniprot.txt DR InterPro; IPR000183; Orn/DAP/Arg_de-COase. |
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Download this section (compressed HTML)Q: Is P. aeruginosa SpeC regulated by an antizyme-like mechanism or by polyamine feedback, and what are its kinetic parameters for ornithine versus lysine?
Q: Is P. aeruginosa SpeC subject to antizyme-like or ribosomal-protein inhibition as reported for E. coli decarboxylases?
Experiment: Purify SpeC and measure ornithine and lysine decarboxylase kinetics, with and without putrescine and spermidine, to confirm substrate specificity and feedback control.
Experiment: Purify recombinant PA4519 and determine kinetic parameters for L-ornithine versus L-lysine and L-arginine to define substrate specificity.
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