Aerobic metabolism of -amino-n-butyric acid by Pseudomonas putida.

Abstract

The aerobic metabolism of β -amino- n -butyric acid was studied with cell-free extracts of a strain of Pseudomonas putida isolated in pure culture through enrichment from a liquid medium containing DL -β- amino -n- butyrate as the sole energy source. The extracts catalyze the decomposition of L -(+)-β- amino -n- butyrate in the presence of pyruvate. D -(−)-β- amino -n- butyrate is not decomposed and does not inhibit the deamination of the L-isomer . The products of the transamination reaction are aceto- acetate and alanine. Experiments on the substrate specificity of the transaminase activity showed that other β - and γ -amino acids can serve as efficient amino donors, whereas corresponding α -amino acids are poor substrates. The further metabolism of acetoacetate is discussed on the basis of the demonstration of acetoacetyl-CoA: succinyl-CoA transferase and acetoacetyl-CoA thiolase activities in the crude extracts as well as activities of glyoxylate cycle enzymes. A complete reaction scheme for the ultimate conversion of β -amino- n -butyric acid to succinate is presented and discussed.