Amino acid racemase with broad substrate specificity,its properties and use in phenylalanine racemization

Summary Broad substrate specificity amino acid racemase (EC 5.1.1.10) was purified from a crude extract of Pseudomonas putida SCRC-744 to near homogeneity. The enzyme has an isoelectric point of 7.6 and a molecular weight of 62,000–65,000. The enzyme showed a broad substrate specificity toward amino acids, utilizing d-glutamine as the best substrate. d-Phenylalanine acted as a substrate to 1% the velocity for d-glutamine. Maximal reaction velocities were observed at 50°–60°C and around pH 8. The apparent K_m values for d-glutamine and d-phenylalanine were 7.8 mM and 25.7 mM, respectively. Both enantiomers of phenylalanine were efficiently racemized by acetone-dried cells of P. putida SCRC-744.