PMID:7040602
| Citation |
Squires, CH, Levinthal, M and De Felice, M (1981) A role for threonine deaminase in the regulation of alpha-acetolactate biosynthesis in Escherichia coli K12. J. Gen. Microbiol. 127:19-25 |
|---|---|
| Abstract |
The flow of carbon to alpha-acetolactate is Escherichia coli K12 is shown to involve the endogenous pool of alpha-ketobutyrate (alpha-KB). In vivo, the acetohydroxy acid synthase (AHAS) isoenzymes have an affinity for alpha-KB sufficiently high that alpha-acetolactate production is severely limited when alpha K-B is supplied exogenously. The ability of threonine deaminase to make alpha-KB is correlated with the synthesis of the AHAS isoenzymes. Mutations in ilvA that alter the catalytic and allosteric properties of threonine deaminase affect alpha-KB production and the expression of the AHAS isoenzymes in a direct way. The ilv A538 mutation results in a feedback-hypersensitive threonine deaminase ans slow alpha-KB and AHAS production. A spontaneous revertant of an ilvA538 strain expressing a feedback-resistant threonine deaminase produces alpha-KB and AHAS more quickly. A physiological role for the activator (valine) site on threonine deaminase is proposed and valine is shown to increase alpha-KB production in vivo. Valine can thus regulate its own biosynthetic pathway without jeopardizing the production of isoleucine. The physiological implications of the role of alpha-KB in the biosynthesis of acetolactate are discussed. |
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| Keywords |
Acetolactate Synthase/biosynthesis; Butyrates/biosynthesis; Butyrates/pharmacology; Escherichia coli/drug effects; Escherichia coli/genetics; Escherichia coli/metabolism; Lactates/biosynthesis; Mutation; Threonine Dehydratase/physiology; Valine/biosynthesis; Valine/pharmacology |
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