High impact information on alpha-Acetohydroxybutyric acid

• The thiamin diphosphate (ThDP)-dependent bio-synthetic enzyme acetohydroxyacid synthase (AHAS) catalyzes decarboxylation of pyruvate and specific condensation of the resulting ThDP-bound two-carbon intermediate, hydroxyethyl-ThDP anion/enamine (HEThDP(-)), with a second ketoacid, to form acetolactate or acetohydroxybutyrate [1].
• Previous data have shown that transcription of the ilvC gene is induced by the acetohydroxy acid isomeroreductase substrates, acetohydroxybutyrate or acetolactate, and that this substrate induction of ilvC expression is mediated by a positive activator encoded by the ilvY gene [2].
• Expression of the ilvC gene is induced by acetohydroxy acid isomeroreductase substrates, acetohydroxybutyrate or acetolactate [3].
• A strain bearing the fusion was shown to be inducible for beta-galactosidase by acetohydroxybutyrate, a natural inducer of acetohydroxy acid isomeroreductase [4].
• This information could in principle be used, together with an independent specific assay for AHB, to determine the composition of an AHAS product mixture; it would, however, be less accurate than a simultaneous chromatographic method [5].

Gene context of alpha-Acetohydroxybutyric acid

• This review deals chiefly with the FAD-dependent, biosynthetic enzymes which readily catalyze the formation of acetohydroxybutyrate from pyruvate and 2-oxobutyrate, as well as of acetolactate from two molecules of pyruvate (the ALS/AHAS group) [6].
• Transcription of the ilvC gene is maintained at a basal level of activity which is elevated as much as 15-fold in the presence of ilvY product and acetohydroxybutyrate [3].

References