SpeH (PA4773) is a prokaryotic class 1a S-adenosylmethionine decarboxylase (AdoMetDC, EC 4.1.1.50) of Pseudomonas aeruginosa. It is made as a 160-residue proenzyme that self-cleaves by serinolysis into a beta and an alpha chain, generating the pyruvoyl group at the alpha-chain N-terminus that forms the catalytic Schiff base. The enzyme decarboxylates S-adenosylmethionine to decarboxylated AdoMet, the aminopropyl donor used by the neighbouring spermidine synthase SpeE2 (PA4774) to convert putrescine into spermidine. PA4773 is the first gene of the PA4773-PA4775 operon, which is induced by extracellular DNA, magnesium limitation and cationic antimicrobial peptides; the spermidine made by this pathway is displayed on the cell surface, where it protects the outer membrane against polymyxin B, aminoglycosides and oxidative damage.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004014 adenosylmethionine decarboxylase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from the PTN002140323 IBD (seeds this gene, M. jannaschii Q57763, S. solfataricus Q9UWY8 and E. coli SpeD P0A7F6). Reason: Core activity; SpeH carries the full prokaryotic class 1a AdoMetDC signature (HAMAP MF_00464) including the pyruvoyl-forming Ser73. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. file:PSEAE/speH/speH-uniprot.txt Belongs to the prokaryotic AdoMetDC family. Type 1 subfamily. |
| GO:0004014 adenosylmethionine decarboxylase activity | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt combined IEA for adenosylmethionine decarboxylase activity. Reason: Consistent with HAMAP family membership. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. |
| GO:0004014 adenosylmethionine decarboxylase activity | IMP PMID:22155771 Surface-localized spermidine protects the Pseudomonas aerugi... | ACCEPT | Summary: PseudoCAP IMP and one of four seeds of the PTN002140323 IBD. The cited abstract describes PA4773 only as an annotated speD homolog; the mutant phenotypes reported are for PA4774 (speE2). No AdoMetDC assay is described. Reason: The claim is correct for this protein on family and active-site evidence, so the row stays consistent with the IBA and IEA rows; whether the IMP itself rests on a PA4773 experiment could not be verified from the abstract, so a CHECK defect is recorded for PseudoCAP. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. PMID:22155771 annotated as homologs of the spermidine synthesis genes speD (PA4773) and speE |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: IBA cytosol from PTN002140323 (seed E. coli SpeD). Reason: A soluble enzyme with no signal peptide or transmembrane segment; cytosolic location is expected for the polyamine biosynthetic enzymes. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. |
| GO:0006596 polyamine biosynthetic process | IEA GO_REF:0000104 | TOO GENERAL | Summary: Polyamine biosynthetic process from UniRule. Reason: Spermidine biosynthetic process (GO:0008295), accepted here, is_a polyamine biosynthetic process. |
| GO:0008295 spermidine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA spermidine biosynthetic process from PTN002140323 (seeds E. coli SpeD and S. solfataricus SpeD). Reason: dcAdoMet is the aminopropyl donor for spermidine synthase; AdoMetDC catalyses the first of the two steps from putrescine to spermidine. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. |
| GO:0008295 spermidine biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: UniProt combined IEA for spermidine biosynthetic process. Reason: As for the IBA row. Supporting Evidence: file:PSEAE/speH/speH-uniprot.txt Catalyzes the decarboxylation of S-adenosylmethionine to S-adenosylmethioninamine (dcAdoMet), the propylamine donor required for the synthesis of the polyamines spermine and spermidine from the diamine putrescine. |
| GO:0016831 carboxy-lyase activity | IEA GO_REF:0000117 | TOO GENERAL | Summary: Carboxy-lyase activity from ARBA. Reason: Adenosylmethionine decarboxylase activity (GO:0004014), accepted here, is_a carboxy-lyase activity. |
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Download this section (compressed HTML)Q: Does a PA4773 (speH) deletion abolish surface spermidine as the PA4774 mutant does, or is AdoMet decarboxylation redundant with another enzyme in P. aeruginosa?
Experiment: Build an in-frame speH deletion, measure intracellular and surface spermidine by HPLC-MS with and without complementation, and assay recombinant SpeH for AdoMet decarboxylase activity and proenzyme self-cleavage.
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