Development of β-Amino Acid Dehydrogenase for the Synthesis of β-Amino Acids via Reductive Amination of β-Keto Acids

Abstract

An l-erythro-3,5-diaminohexanoate dehydrogenase from Candidatus Cloacamonas acidaminovorans (3,5-DAHDHcca) was engineered to β-amino acid dehydrogenase (β-AADH) by screening a domain scanning mutagenesis library. The best β-AADH mutant displayed about 200-fold activity toward (R)-β-homomethionine compared with the wild-type enzyme. (R)-β-Homomethionine, (R)-β-phenylalanine, and (S)-β-aminobutyric acid were obtained via β-AADH-catalyzed reductive amination of the corresponding β-keto acids, which were generated from β-keto-nitriles or β-keto-esters with nitrilase or lipase. This is the first example of the direct reductive amination of β-keto acids catalyzed by β-AADH to give β-amino acids, opening a new venue for the synthesis of chiral β-amino acids.