222] Amino acid racemase (Pseudomonas striata)

Abstract

This chapter discusses the methods of preparation of Amino Acid Racemase (Pseudomonas striata). Amino acid racemase catalyzes the conversion of either D- or L-amino acids to the racemates. All assay methods are based on the measurement of one stereoisomer of the substrate. When the L-amino acids whose D-isomer are susceptible to D-amino acid oxidase are used as the substrates, the amino acid racemase activity is followed by manometric determination of the D-amino acids formed with D-amino acid oxidase. L-Glutamate decarboxylase or L-lysine decarboxylase is used to determine the activity in the reaction mixtures containing D-glutamate or D-lysine, respectively, as the substrate. Determination of the activity catalyzing the racemization of arginine is performed by measuring the formation of L-arginine from the D-isomer with arginase. The substrate specificity of the enzyme is extremely low in comparison with usual amino acid racemases thus far reported—for example, proline racemase. The enzyme activity is inhibited by D-cycloserine and hydroxylamine.