Synthesis of the enzymes of the mandelate pathway by Pseudomonas putida. 3. Isolation and properties of constitutive mutants.

Hegeman, G. D. (University of California, Berkeley). Synthesis of the enzymes of the mandelate pathway by Pseudomonas putida. III. Isolation and properties of constitutive mutants. J. Bacteriol. 91:1161-1167. 1966.-Mutants of Pseudomonas putida constitutive for the synthesis of l(+)-mandelate dehydrogenase were obtained after mandelate- or benzoylformate-limited growth in a chemostat. When grown in media noninducing for the wild type, the mutants are capable of coordinate, constitutive synthesis of the first five enzymes of the mandelate pathway. Later enzymes of the pathway that were examined are normally repressed. The constitutive mutants have two other noteworthy properties: they are superinducible by some compounds which induce the mandelate group enzymes in the wild type, or as a result of exhaustion of the carbon and energy source of the medium in which they are grown; and they exhibit a decreased specificity of induction, being inducible by a wide range of compounds devoid of inductive function for the wild type. These results, together with other evidence indicating that the five mandelate group enzymes comprise a regulatory unit, are discussed and evaluated in the context of the general problem of the regulation of complex dissimilatory pathways.