Biochemical and Structural Characterization of an (R)‐Selective Transaminase in the Asymmetric Synthesis of Chiral Hydroxy Amines

Abstract An ( R )‐selective transaminase Rb TA with excellent stereoselectivity (>99% ee ) in the asymmetric amination of hydroxy ketones was identified. Biochemical characterization showed that Rb TA exhibited the highest activity toward 4‐hydroxy‐2‐butanone among reported enzymes, and that it has broad substrate specificity, including for aliphatic, aromatic, and alicyclic ketones. Crystallization of Rb TA were performed, as were molecular docking and mutagenesis studies. Residue Tyr125 plays a key role in substrate recognition by forming a hydrogen bond with hydroxy ketone. The applicability of the enzyme was determined in preparative‐scale synthesis of ( R )‐3‐amino‐1‐butanol, demonstrating the potential of Rb TA as a green biocatalyst for production of value‐added chiral hydroxy amines. This study provides an efficient tool for enzymatic synthesis of chiral hydroxy amines, as well as structural insight into substrate recognition by transaminases in the asymmetric amination of hydroxy ketones. magnified image