d-Amino Acids as Inducers of l-Alanine Dehydrogenase in Bacillus subtilis

• Published in: The Journal of biological chemistry 1968-03, Vol.243 (5), p.1006-1011
• Main Authors: Berberich, R, Kaback, M, Freese, E
• Format: Article
• Language: English
• Subjects: Alanine - metabolism; Alanine Transaminase; Amino Acid Oxidoreductases - biosynthesis; Bacillus subtilis - enzymology; Carbon Isotopes; Enzyme Induction; Isomerases; Phenylalanine - metabolism; Pyruvates - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)93614-8

l -Alanine dehydrogenase in Bacillus subtilis is inducible by its substrate, l -alanine. In addition to l -alanine, 10 other l -amino acids as well as d -alanine and 11 other d -amino acids are also inducers. The physiological role of the enzyme is to catabolize l -alanine to pyruvate and ammonia. The majority of the l -amino acid inducers can be converted to l -alanine by l -alanine transaminase. Similarly, the majority of the d -amino acid inducers can be converted to d -alanine by d -alanine transaminase. l - and d -Alanine, in turn, are interconvertible by alanine racemase. In a mutant deficient in alanine racemase, neither l -alanine nor any of the other l -amino acid inducers can induce l -alanine dehydrogenase, whereas the enzyme is still inducible by d -alanine and the other d -amino acid inducers. These results show that the l -amino acids induce l -alanine dehydrogenase only if they can be converted first to l -alanine and then to d -alanine. The pattern of control observed illustrates a new form of end product regulation, whereby d -alanine regulates its own biosynthesis via alanine racemase by the induction of l -alanine dehydrogenase. l -Alanine dehydrogenase catabolizes l -alanine, and thereby limits the amount of l -alanine available to alanine racemase for the synthesis of d -alanine.