The regulation of the butanediol cycle in Bacillus subtilis

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The existence of a functional butanediol cycle in Bacillus subtilis was demonstrated. Acetate is the end-product of the reactions of this cycle. Aceton is converted to 2 molecules of acetate when dissimilated. Medium conditions strongly affect the synthesis of the enzymes necessary to maintain a functional cycle. Acetonin stimulates synthesis of acetoin dehydrogenase and diacetylmethylcarbinol synthase. Glucose anatagonizes this effect by catabolite repression of their synthesis. Synthesis of the enzymes diacetylmethylcarbinol reductase, butanediol dehydrogenase and diacetyl reductase is in contrast to the above two catabolite-induced enzymes. Acetoin does not have any regulatory effect. The reaction from acetoin to diacetyl is apparently catalysed by a different enzyme—acetoin dehydrogenase—as is the reverse reaction: diacetyl reductase. Glucose induces the synthesis of the second and represses the synthesis of the first enzyme, acetoin induces the synthesis of the first enzyme, but does not affect the second.