The isolation, identification and properties of isochorismic acid. An intermediate in the biosynthesis of 2,3-dihydroxybenzoic acid

Young, Ian G.; Batterham, T. J.; Gibson, F.

doi:10.1016/0304-4165(69)90301-8

Cited by 82 publications

(32 citation statements)

References 22 publications

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“…Non-enzymatic Synthesis of SA from Isochorismate Is Negligible-Non-enzymatic conversion of IC to SA (ϳ25% conversion, 100°C, 10 min) has long been reported (60,63). Therefore, using our findings (above) regarding the subcellular localization and biochemical properties of AtICS1, we directly examined the potential for non-enzymatic formation of SA from IC (produced via AtICS1) under physiological conditions.…”

Section: Ref 5)mentioning

confidence: 90%

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Strawn

Marr

Inoue

et al. 2007

Journal of Biological Chemistry

219

146

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Salicylic acid (SA) is a phytohormone best known for its role in plant defense. It is synthesized in response to diverse pathogens and responsible for the large scale transcriptional induction of defense-related genes and the establishment of systemic acquired resistance. Surprisingly, given its importance in plant defense, an understanding of the underlying enzymology is lacking. In Arabidopsis thaliana, the pathogen-induced accumulation of SA requires isochorismate synthase (AtICS1). Here, we show that AtICS1 is a plastid-localized, stromal protein using chloroplast import assays and immunolocalization. AtICS1 acts as a monofunctional isochorismate synthase (ICS), catalyzing the conversion of chorismate to isochorismate (IC) in a reaction that operates near equilibrium (K eq ‫؍‬ 0.89). It does not convert chorismate directly to SA (via an IC intermediate) as does Yersinia enterocolitica Irp9. Using an irreversible coupled spectrophotometric assay, we found that AtICS1 exhibits an apparent K m of 41.5 M and k cat ‫؍‬ 38.7 min ؊1 for chorismate. This affinity for chorismate would allow it to successfully compete with other pathogen-induced, chorismate-utilizing enzymes. Furthermore, the biochemical properties of AtICS1 indicate its activity is not regulated by light-dependent changes in stromal pH, Mg 2؉ , or redox and that it is remarkably active at 4°C consistent with a role for SA in cold-tolerant growth. Finally, our analyses support plastidic synthesis of stress-induced SA with the requirement for one or more additional enzymes responsible for the conversion of IC to SA, because non-enzymatic conversion of IC to SA under physiological conditions was negligible.

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Section: Ref 5)mentioning

confidence: 90%

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Strawn

Marr

Inoue

et al. 2007

Journal of Biological Chemistry

219

146

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“…The fluorometric assay commonly used for the assay of isochorismate synthase (31,39) failed to show enzymatic activity in the entC mutant. Since the fluorometric assay measures only 25% of the isochorismate formed after its thermal conversion to salicylic acid (39), it is not sensitive enough to detect the low levels of the activity expected.…”

Section: Methodsmentioning

confidence: 99%

Anaerobic biosynthesis of enterobactin Escherichia coli: regulation of entC gene expression and evidence against its involvement in menaquinone (vitamin K2) biosynthesis

1996

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In Escherichia coli, isochorismate is a common precursor for the biosynthesis of the siderophore enterobactin and menaquinone (vitamin K 2 ). Isochorismate is formed by the shikimate pathway from chorismate by the enzyme isochorismate synthase encoded by the entC gene. Since enterobactin is involved in the aerobic assimilation of iron, and menaquinone is involved in anaerobic electron transport, we investigated the regulation of entC by iron and oxygen. An operon fusion between entC with its associated regulatory region and lacZ ؉ was constructed and introduced into the chromosome in a single copy. Expression of entC-lacZ was found to be regulated by the concentration of iron both aerobically and anaerobically. An established entC::kan mutant deficient in enterobactin biosynthesis was found to grow normally and synthesize wild-type levels of menaquinone under anaerobic conditions in iron-sufficient media. These results led to the demonstration of an alternate isochorismate synthase specifically involved in menaquinone synthesis encoded by the menF gene. Consistent with these findings, the entC ؉ strains were found to synthesize enterobactin anaerobically under iron-deficient conditions while the ent mutants failed to do so.

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“…For these experiments, the incubation was shortened to 3 min in order to measure accurately the initial reaction velocities and to minimize productinhibition effects. When chorismate was replaced with 47 pM isochorismate (Young et a/., 1969) as substrate, no formation of salicylic acid could be detected, showing this pyruvate-lyase reaction to be specific for chorismate.…”

Section: Properties Of Cplmentioning

confidence: 97%

Formation of 4-hydroxybenzoate in Escherichia coli: characterization of the ubiC gene and its encoded enzyme chorismate pyruvate-lyase

Siebert

Severin

Heide³

1994

Microbiology

104

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The isolation, identification and properties of isochorismic acid. An intermediate in the biosynthesis of 2,3-dihydroxybenzoic acid

Cited by 82 publications

References 22 publications

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Arabidopsis Isochorismate Synthase Functional in Pathogen-induced Salicylate Biosynthesis Exhibits Properties Consistent with a Role in Diverse Stress Responses

Anaerobic biosynthesis of enterobactin Escherichia coli: regulation of entC gene expression and evidence against its involvement in menaquinone (vitamin K2) biosynthesis

Formation of 4-hydroxybenzoate in Escherichia coli: characterization of the ubiC gene and its encoded enzyme chorismate pyruvate-lyase

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