Semirational Design of an Engineered Amine Dehydrogenase Enables Enantioselectivity Inversion for 4-Phenylbutan-2-amine and Its Derivatives

Using 4-phenylbutan-2-one as the model substrate, an (R)-enantiospecific AmDH (M0) derived from l-amino acid dehydrogenase was converted into (S)-enantioselective enzymes (M4–M7) through several rounds of semirational iterative mutations. Variants M6-1 and M7 were successfully applied to synthesize (S)-amines (70–81% yields) and (R)-β-amino alcohols (60–65% yields) with 95% to >99% ee. Molecular dynamics simulations provided insights into the role of mutations in substrate recognition and stereoselective control, offering important guidance for regulating the stereoselectivity of AmDHs through protein engineering.