PA0305 (named HacB by its characterizers) is a peptidase S45 (penicillin acylase family) N-terminal nucleophile hydrolase of Pseudomonas aeruginosa, a paralog of the AHL acylases PvdQ and QuiP and closely similar to HacB of Pseudomonas syringae. The purified protein is processed into alpha and beta subunits, with the catalytic serine at the N-terminus of the beta subunit. It is an acyl-homoserine lactone (AHL) acylase (EC 3.5.1.97) that degrades AHLs with acyl chains of 6 to 14 carbons and is most efficient on the Las signal 3-oxo-C12-HSL. Overexpression lowers 3-oxo-C12-HSL and virulence factor production, so it can act as a quorum quencher; unlike QuiP it is not needed for growth on AHLs. It is probably periplasmic, like its paralogs.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016787 hydrolase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: True but uninformative; GO:0016811, accepted below, is a descendant. Reason: GO:0016811 is_a GO:0016810 is_a GO:0016787 and is accepted in this review. |
| GO:0016811 hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds, in linear amides | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from the PTN002151232 IBD seeded by PvdQ, QuiP and PA0305 itself; the self-seed reflects PA0305's own purified-enzyme evidence and is not circular. Reason: Sound IBD; GO:0016811 is the most specific existing term for AHL acylase and suits the clade (node record in the pvdQ notes). Supporting Evidence: PMID:21372094 Using a biosensor assay, PA0305his was shown to degrade AHLs with acyl side chains ranging in length from 6 to 14 carbons. |
| GO:0016811 hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds, in linear amides | IDA PMID:21372094 PA0305 of Pseudomonas aeruginosa is a quorum quenching acylh... | ACCEPT | Summary: PseudoCAP IDA seed of PTN002151232. The purified protein degrades long-chain AHLs with measured kcat/Km values (abstract). Reason: Direct purified-enzyme evidence for AHL acylase activity. Supporting Evidence: PMID:21372094 the pa0305 gene encodes an efficient acylase with activity towards long-chain homoserine lactones |
| GO:0016811 hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds, in linear amides | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO mapping from the Pen/GL7ACA/AHL acylase signatures; agrees with the experimental row. Reason: Consistent with the IDA and IBA rows on the same term. Supporting Evidence: PMID:21372094 Using a biosensor assay, PA0305his was shown to degrade AHLs with acyl side chains ranging in length from 6 to 14 carbons. |
| GO:0017000 antibiotic biosynthetic process | IEA GO_REF:0000002 | REMOVE | Summary: InterPro2GO mapping from the peptidase S45 signature, reflecting the industrial use of penicillin acylases. PA0305 is characterized as an AHL acylase; nothing links it to antibiotic synthesis. Reason: Over-propagated family mapping; the demonstrated activity is AHL deacylation. Supporting Evidence: PMID:21372094 the pa0305 gene encodes an efficient acylase with activity towards long-chain homoserine lactones |
| GO:0042597 periplasmic space | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt's periplasm statement is an ARBA prediction. The N-terminus (MKRTLTVIAVAVAAAAAGGAWYLH) looks like a Sec signal peptide, and the characterized paralogs are periplasmic. Reason: Plausible by sequence and family; not directly assayed (see notes). Supporting Evidence: file:PSEAE/PA0305/PA0305-notes.md consistent with a Sec signal peptide as in its periplasmic paralogs PvdQ and QuiP |
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Download this section (compressed HTML)Q: Under what conditions is PA0305 expressed in P. aeruginosa, and does it contribute to native AHL turnover given that it is dispensable for growth on AHLs?
Experiment: Confirm the periplasmic location of PA0305 by fractionation or a PhoA fusion, and measure 3-oxo-C12-HSL levels in a deletion mutant under conditions where pa0305 is expressed.
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