Demonstration of Imino Acids as Products of the Reactions Catalyzed by D- and L-Amino Acid Oxidases

摘要

It had long been thought, but never demonstrated, that imino acids are formed in the reactions catalyzed by D- and L-amino acid oxidases (EC 1.4.3.3 and 1.4.3.2). The formation of imino acids is now shown directly by allowing the amino acid oxidase reaction to proceed in the presence of NaBH4, when the imino acid is reduced to the corresponding racemic amino acid. Thus, when NaBH4 is added to a mixture of D-amino acid oxidase and D-alanine, a significant amount of L-alanine is formed. Analogous results are obtained using L-amino acid oxidase and L-leucine. Since D-amino acid oxidase is active in the presence of NaBH4, L-alanine continues to be formed until most of the D-isomer is oxidized by the enzyme. This reaction provides a new method for inverting the configuration of an amino acid.