Enzymatic Racemization of Amines Catalyzed by Enantiocomplementary ω-Transaminases

A strategy for the biocatalytic racemization of primary alpha-chiral amines was developed by employing a pair of stereocomplementary PLP-dependent omega-transaminases. The interconversion of amine enantiomers proceeded through reversible transamination by a prochiral ketone intermediate, either catalyzed by a pair of stereocomplementary omega-transaminases or by a single enzyme possessing low stereoselectivity. To tune the system, the type and concentration of a nonchiral amino acceptor proved to be crucial. Finally, racemization could be achieved by the cross-transamination of two different amines without a requirement for an external amino acceptor. Several synthetically and industrially important amines could be enzymatically racemized under mild reaction conditions.