Regulation of expression of novel mandelate dehydrogenases in mutants of Acinetobacter calcoaceticus.

Wild-type strains of Acinetobacter calcoaceticus able to grow on only L(+)- or D(-)-mandelate gave rise to mutants that could grow on the other isomer of mandelate. Each mutant contained an additional mandelate dehydrogenase which was not expressed in the parent strain. The novel enzymes were shown to be controlled co-ordinately with the pre-existing enzymes for the conversion of mandelate into benzoate when induced with phenylglyoxylate, gratuitously induced with thiophenoxyacetate, subjected to anti-induction by 2-phenylpropionate or catabolite-repressed by succinate. Mutants which had been selected on the basis of possession of a constitutive phenylglyoxylate decarboxylase also constitutively expressed both the original and the novel mandelate dehydrogenases.