Methionine degradation by Pseudomonas fluorescens UK1 and its methionine-utilizing mutant

Pseudomonas fluorescens UK1, and a mutant derived from it that can use methionine as its sole source of carbon and nitrogen, were used to study methionine degradation. Radioactive 2-oxomethionine, 2-oxobutyric acid and carbon dioxide comprised 95% of [I-14C]methionine consumed by the mutant. Demethiolating activity was detected in both strains when they were grown with methionine. The ability to grow on methionine depended on the decarboxylation of 2-oxobutyric acid derived from it. This decarboxylating activity was lost if the growth media contained an additional carbon source. No evidence was obtained for the operation of the cystathionine pathway.