Enzymatic Synthesis of (S)-Phenylalanine and Related (S)-Amino Acids by Phenylalanine Dehydrogenase

Phenylalanine dehydrogenase (L-phenylalanine: NAD⁺ oxidoreductase, deaminating [EC 1.4.1.20], PheDH) from Bacillus sphaericus R79a, overproduced in Escherichia coli JM109/pBPDH1-DBL, is active toward 3-substituted pyruvic acids with bulky substituents in the reductive amination reaction. Optically pure (S)-phe and other (S)-amino acids are quantitatively synthesized from their oxo-analogs using PheDH, with a regeneration of NADH by formate dehydrogenase from Candida boidinii No. 2201. Acetone-dried cells of B. sphaericus R79a and C. boidinii No. 2201 are also effective for (S)-phe synthesis, providing a simple microbial method of synthesis.