Regulation of the Enzymes of the β‐Ketoadipate Pathway in Moraxella calcoacetica

Further evidence for coordinacy of enzymes operative in the protocatechuate branch of the β‐ketoadipate pathway in Moraxella calcoacetica has been obtained through studies with an analog of protocatechuate, 3‐hydroxy‐4‐methylbenzoate. This compound, which is not metabolizable by M. calcoacetica , inhibits the induced synthesis of shikimate dehydrogenase, protocatechuate oxygenase, carboxymuconate lactonizing enzyme, carboxymuconolactone decarboxylase, β‐ketoadipate enol‐lactone hydrolase I and β‐ketoadipate succinyl‐CoA transferase I, by the wild type. It also effectively abolishes constitutive synthesis of these enzymes by mutants with impaired protocatechuate oxygenase function. Mutants in which the regulatory control of these enzymes is modified have been isolated. Such mutants are still inducible, but are very poorly induced by protocatechuate, the metabolite which is the normal inducer of these enzymes in the wild type. However, 3‐hydroxy‐4‐methylbenzoate, which interferes with induction in the wild type, has become an effective inducer for the mutants.