PA4921 (ChoE) is a 307-aa SGNH/GDSL-family hydrolase of Pseudomonas aeruginosa with an N-terminal signal peptide, and is the enzyme responsible for the cholinesterase activity of strain PAO1. The purified recombinant enzyme hydrolyses acetylthiocholine and propionylthiocholine, with substrate inhibition and kinetics resembling mammalian acetylcholinesterases, and also hydrolyses p-nitrophenyl propionate and butyrate less efficiently; butyrylcholine is an inhibitor. Through its acyl-enzyme intermediate it can also transfer acetyl groups to amines and alcohols. Many crystal structures of the mature enzyme are available. ChoE is thought to let the bacterium release choline from host acetylcholine.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004104 cholinesterase activity | IDA PMID:22192836 A Pseudomonas aeruginosa PAO1 acetylcholinesterase is encode... | ACCEPT | Summary: PseudoCAP IDA and one of two seeds of the PTN005219546 carboxylic ester hydrolase IBD. The purified recombinant enzyme hydrolyses acetyl- and propionylthiocholine. Reason: Seed verdict SOUND. Purified-enzyme kinetics directly support cholinesterase activity; whether the physiological substrate is acetylcholine or propionylcholine is unresolved, so this parent term is the right level rather than GO:0003990. Supporting Evidence: PMID:22192836 Acetylthiocholine (ATC) and propionylthiocholine (PTC) are substrates of this enzyme, but butyrylcholine is an inhibitor. PMID:22192836 Studies performed with the purified recombinant enzyme indicated that the substrate saturation curves and the catalytic mechanism are similar to those properties described for mammalian AchEs. |
| GO:0008610 lipid biosynthetic process | IBA GO_REF:0000033 | REMOVE | Summary: IBA from the PTN005219546 GO:0008610 IBD, whose only seed is EstA (O33407); PA4921 is not a seed of this term. Reason: The EstA seed records that an estA deletion makes little rhamnolipid, a necessity phenotype of an outer-membrane esterase, not participation in lipid synthesis. Even if it held for EstA, nothing links ChoE, a secreted cholinesterase, to lipid biosynthesis. The node-level GO_CENTRAL defect is recorded once in the estA review (genes/PSEAE/estA); not repeated here. Propagation Review Root cause: SOURCE BAD Failure modes: ROLE CONFLATION FUNCTIONAL DIVERGENCE Sources checked: PANTHER:PTN005219546 · PTN005219546 SOURCE BAD Sole-seeded process IBD on a GDSL esterase node of 960 leaves; see the estA review for the GO_CENTRAL defect. UniProtKB:O33407 · EstA (sole seed) SOURCE WEAK OR INFERRED UniProt IMP GO:0008610 from PMID:17631636, a rhamnolipid-deficiency phenotype of an estA deletion. It does not show participation, and does not transfer to a cholinesterase. Supporting Evidence: PMID:17631636 This report is focused on the influence of the outer membrane-bound esterase EstA of P. aeruginosa PAO1 on rhamnolipid production. PMID:22192836 this work demonstrates that the PA4921 gene of the Pseudomonas aeruginosa PAO1 genome is a gene responsible for cholinesterase (ChoE) activity |
| GO:0016788 hydrolase activity, acting on ester bonds | IEA GO_REF:0000120 | TOO GENERAL | Summary: InterPro GDSL and ARBA mapping to a generic esterase term. Reason: True but uninformative; GO:0004104 cholinesterase activity, accepted here, is_a GO:0016788. |
| GO:0052689 carboxylic ester hydrolase activity | IBA GO_REF:0000033 | TOO GENERAL | Summary: IBA from the two-seed PTN005219546 node (EstA and PA4921). PA4921 appears in its own WITH/FROM because of its IDA row, which is expected. Reason: The node term is sound for a GDSL/SGNH esterase clade and stands on EstA alone (purified-enzyme esterase evidence), but for this gene GO:0004104 cholinesterase activity, accepted here, is_a GO:0052689, so the inherited term adds nothing. |
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Download this section (compressed HTML)Q: Is the physiological substrate acetylcholine (host-derived) or propionylcholine, and does ChoE contribute choline for osmoprotection or carbon/nitrogen nutrition in vivo?
Experiment: Compare growth and choline uptake of a PA4921 deletion and complemented strains on acetylcholine as sole carbon/nitrogen source, and measure kcat/Km for acetylcholine versus propionylcholine with the purified enzyme.
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