Creation of a (R)-β-Transaminase by Directed Evolution of D-Amino Acid Aminotransferase

fi-Transaminases (fi-TAs) have shown considerable potential as biocatalysts for the synthesis of chiral fi- and y-amino acid. Herein, a (R)-fi-TA was successfully created by the directed evolution of D-amino acid amino-transferase. The specific activities of created (R)-fi-TA for fi-phenylalanine (1.74 U/mg) and y-phenylbutanoic acid (1.67 U/mg) were comparable with those of naturally occurring (S)-fi-TAs. Moreover, the designed (R)-fi-TA also showed potential for the biocatalytic synthesis of a 6-amino acid with specific activity (0.23 U/mg), which has not yet been explored. Enantiopure (S)-and (R)-forms of various fi-, y- and 6-amino acids (>99% ee) were synthesized using engineered (R)-fi-TA-mediated kinetic resolution and asymmetric synthesis, respectively.