PMID:6351926
| Citation |
Gollop, N, Chipman, DM and Barak, Z (1983) Inhibition of acetohydroxy acid synthase by leucine. Biochim. Biophys. Acta 748:34-9 |
|---|---|
| Abstract |
The enzymatic reaction of acetohydroxy acid synthase in crude extracts of Escherichia coli K-12 is inhibited by leucine. Inhibition is most pronounced at low pH values and is low at pH values higher than 8.0. Both isoenzymes of acetohydroxy acid synthase present in E. coli K-12 (isoenzyme I and isoenzyme III) are inhibited by leucine. Isoenzyme I, which is responsible for the majority of acetohydroxy acid synthase activity in E. coli K-12 at physiological pH, is inhibited almost completely by 30 mM leucine at pH 6.25-7.0 and is not affected at all at pH values higher than 8.4. Inhibition of isoenzyme I by leucine is a mixed noncompetitive process. Leucine inhibition of isoenzyme III is pH-independent and reaches only 40% at 30 mM leucine. The inhibition of acetohydroxy acid synthase by leucine at physiological pH, observed in vitro in this study, correlates with the idea that acetohydroxy acid synthase is a target for the toxicity of the abnormally high concentrations of leucine in E. coli K-12. |
| Links | |
| Keywords |
Acetolactate Synthase/antagonists & inhibitors; Escherichia coli/enzymology; Escherichia coli/genetics; Genotype; Isoenzymes/antagonists & inhibitors; Kinetics; Leucine/pharmacology; Oxo-Acid-Lyases/antagonists & inhibitors; Phenotype; Species Specificity |
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