Engineered Aminotransferase for the Production of d-Phenylalanine Derivatives Using Biocatalytic Cascades

d-Phenylalanine derivatives are valuable chiral building blocks for a wide range of pharmaceuticals. Here, we developed stereoinversion and deracemization biocatalytic cascades to synthesize d-phenylalanine derivatives that contain electron-donating or -withdrawing substituents of various sizes and at different positions on the phenyl ring with a high enantiomeric excess (90 to >99 % ee) from commercially available racemic mixtures or l-amino acids. These whole-cell systems couple Proteus mirabilis l-amino acid deaminase with an engineered aminotransferase that displays native-like activity towards d-phenylalanine, which we generated from Bacillus sp. YM-1 d-amino acid aminotransferase. Our cascades are applicable to preparative-scale synthesis and do not require cofactor-regeneration systems or chemical reducing agents.