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.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
