Isolation and properties of a beta-alanine transaminaseless mutant of Pseudomonas fluorescens

beta-Alanine catabolism in Pseudomonas fluorescens is initiated by the enzyme beta-alanine transaminase. We have isolated mutants which fail to produce this enzyme and thus cannot grow on beta-alanine as the sole nitrogen source. The accumulation of beta-alanine-1-(14)C has been studied in one of these mutants, strain 67, and in the wild type. In the mutant, beta-alanine remains in a stable intracellular pool, whereas in the wild type conversion of beta-alanine to an intermediate, presumably malonate semialdehyde, and to CO(2) can be detected. The membrane transport system for beta-alanine can be conveniently studied in this transaminaseless mutant.