The Isolation of Pleiotropic Mutants of Pseudomonas aminovorans Deficient in the Ability to Grow on Methylamine and an Examination of their Enzymic Constitution

Abstract

Summary: Mutants deficient in several enzymes of methylamine oxidation and assimilation have been obtained by treating Pseudomonas aminovorans with ultraviolet light. One of these mutants was studied in detail and was shown to lack the enzymes of trimethylamine and dimethylamine oxidation. In addition, activities of the following enzymes, all postulated as being involved in C1 metabolism, were lost: hydroxypyruvate reductase, serine-glyoxylate aminotransferase, isocitrate lyase, phosphoeno/pyruvate carboxylase, N-methylglutamate dehydrogenase, γ-glutamylmethylamide synthetase, formate dehydrogenase and dye-linked formaldehyde dehydrogenase. In contrast, three enzymes - NAD+,glutathione-linked formaldehyde dehydrogenase, N-methylalanine dehydrogenase and N-methylglutamate synthase - were retained. This phenotype suggests either a lesion in a regulatory gene, a deletion in an early structural gene of an operon or the loss of a plasmid. Results obtained indicated that P. aminovorans possesses an isocitrate lyase-serine pathway.