pchA

Gene Description

PchA (PA4231) is the isochorismate synthase of Pseudomonas aeruginosa, the first enzyme of the pathway that makes salicylate and the siderophore pyochelin. Encoded as the last gene of the iron-repressed pchDCBA operon, it is a 52-kDa Mg2+-dependent monomer of the chorismate-utilizing enzyme family that converts chorismate to isochorismate; the isochorismate pyruvate-lyase PchB then converts isochorismate to salicylate and pyruvate. PchA is rate-limiting for salicylate formation, and its cellular concentration, set at the transcriptional level by iron (negative) and pyochelin (positive), controls flux into pyochelin biosynthesis.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0008909 isochorismate synthase activity	IBA GO_REF:0000033	ACCEPT	Summary: IBA from PTN000132907 (isochorismate synthase clade, 2 seeds, 17 leaf IBAs). Seeds are E. coli EntC (P0AEJ2, IDA/EXP) and PchA itself (PseudoCAP IDA, PMID:12624097). Reason: PchA has its own purified-enzyme kinetics for this activity, and the node term suits an isochorismate synthase clade; the IBD would stand on E. coli EntC alone. Supporting Evidence: PMID:12624097 At pH 7.0, the optimum, a K(m) = 4.5 microm and a k(cat) = 43.1 min(-1) were determined for chorismate.
GO:0008909 isochorismate synthase activity	IDA PMID:12624097 Isochorismate synthase (PchA), the first and rate-limiting e...	ACCEPT	Summary: PseudoCAP IDA, the PTN000132907 seed row. PchA was purified to homogeneity from P. aeruginosa and its Mg2+-dependent kinetics with chorismate were determined. Reason: Seed verdict SOUND; direct assay of the purified gene product. Supporting Evidence: PMID:12624097 The PchA protein was purified to apparent electrophoretic homogeneity from a PchA-overexpressing P. aeruginosa strain. PMID:12624097 At pH 7.0, the optimum, a K(m) = 4.5 microm and a k(cat) = 43.1 min(-1) were determined for chorismate.
GO:0008909 isochorismate synthase activity	IEA GO_REF:0000120	ACCEPT	Summary: Combined automated isochorismate synthase activity. Reason: Same claim as the IDA row. Supporting Evidence: PMID:12624097 At pH 7.0, the optimum, a K(m) = 4.5 microm and a k(cat) = 43.1 min(-1) were determined for chorismate.
GO:0009697 salicylic acid biosynthetic process	IDA PMID:7500944 Structural genes for salicylate biosynthesis from chorismate...	ACCEPT	Summary: Salicylate formation from chorismate required pchA together with pchB, in an E. coli entC mutant and in extracts with overproduced PchA and PchB. Reason: PchA catalyses the first of the two steps from chorismate to salicylate, so it does part of the work of the process. Supporting Evidence: PMID:7500944 Our results are consistent with a pathway leading from chorismate to isochorismate and then to salicylate plus pyruvate, catalyzed consecutively by the iron-repressible PchA and PchB proteins in P. aeruginosa.
GO:0009697 salicylic acid biosynthetic process	IEA GO_REF:0000041	ACCEPT	Summary: UniPathway salicylate biosynthesis. Reason: Same claim as the IDA row. Supporting Evidence: PMID:7500944 Our results are consistent with a pathway leading from chorismate to isochorismate and then to salicylate plus pyruvate, catalyzed consecutively by the iron-repressible PchA and PchB proteins in P. aeruginosa.
GO:0042864 pyochelin biosynthetic process	IDA PMID:12624097 Isochorismate synthase (PchA), the first and rate-limiting e...	ACCEPT	Summary: PchA is the first enzyme of the pyochelin pathway; overexpressing pchA raised both salicylate and pyochelin production. Reason: PchA catalyses the committed first step of pyochelin biosynthesis (chorismate to isochorismate), so it takes part in the process. Supporting Evidence: PMID:12624097 In cultures grown in iron-limiting media to high cell densities, overexpression of the pchA gene resulted in overproduction of salicylate as well as in enhanced pyochelin formation.

Gene Description

Existing Annotations Review

Core Functions

Isochorismate synthase that converts chorismate to isochorismate, the first and rate-limiting step of salicylate and pyochelin siderophore biosynthesis.

References

📚 Additional Documentation

Notes

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