Alanine dehydrogenase of the β-lactam antibiotic producer Streptomyces clavuligerus

l-Alanine dehydrogenase was found in extracts of the antibiotic producer Streptomyces clavuligerus. The enzyme was induced by ammonia, and the level of induction was dependend on the extracellular concentration. l-Alanine was the only amino acid able to induce alanine dehydrogenase. The enzyme was characterized from a 38-fold purified preparation. Pyruvate (K_m=1.1 mM), ammonia (K_m=20 mM) and NADH (K_m=0.14 mM) were required for the reductive amination, and l-alanine (K_m=9.1 mM) and NAD (K_m=0.5 mM) for the oxidative deaminating reaction. The aminating reaction was inhibited by alanine, serine and NADPH. Alanine inhibited uncompetitively with respect to NADH (K_i=1.6 mM) and noncompetitively with respect to ammonia (K_i=2.0 mM) and pyruvate (K_i=3.0 mM). In the aminating reaction 3-hydroxypyruvate, glyoxylate and 2-oxobutyrate could partially (6-7%) substitute pyruvate. Alanine dehydrogenase from S. clavuligerus differed with respect to its molecular weight (92000) and its kinetic properties from those described for other microorganisms.