Scheme 1. Reaction Mechanism of Wild-Type AMDase and Its Variants with Inverted Enantioselectivity (When Introducing the G74C Substitution, i.e., Swapping the Catalytic Cysteine from Position 188 to Position 74) and Promiscuous Racemic Activity (When Introducing/Maintaining Cysteines at Both Positions 74 and 188 Simultaneously).

The pro-(R) carboxylate is shown in black, and the pro-(S) carboxylate in red.