Oxidation of D- and L-valine by enzymes of Pseudomonas aeruginosa.

Norton, J. E. (University of Oklahoma School of Medicine, Oklahoma City), and J. R. Sokatch. Oxidation of d- and l-valine by enzymes of Pseudomonas aeruginosa. J. Bacteriol. 92:116-120. 1966.-Cell-free extracts prepared from Pseudomonas aeruginosa grown on dl-valine catalyzed the consumption of oxygen with several d-amino acids, but not with the corresponding l-amino acids. The product of d-valine oxidation was identified as 2-oxoisovalerate by the preparation and characterization of 2-oxoisovalerate 2,4-dinitrophenylhydrazone. The enzyme catalyzing d-amino acid oxidation was present in extracts of cells grown on valine, but not on glucose, had a pH optimum of approximately 9.0, consumed 1 atom of oxygen per mole of keto acid produced, and was not stimulated by any of the usual electron transport cofactors. It was not possible to demonstrate either the direct oxidation of l-valine or the conversion of l- to d-valine by these enzyme preparations. However, a possible route of l-valine metabolism by transamination with 2-oxoglutarate with regeneration of the amino group acceptor by glutamate oxidation was established by identification of the transaminase and l-glutamate dehydrogenase in these enzyme preparations.