An alcohol dehydrogenase LkADH was successfully engineered to exhibit improved activity and substrate tolerance for the production of (S)-2-chloro-1-(3,4-difluorophenyl)ethanol, an important precursor of ticagrelor. Five potential hotspots were identified for enzyme mutagenesis by using natural residue abundance as an indicator to evaluate their potential plasticity. A semi-rational strategy named "aromatic residue scanning" was applied to randomly mutate these five sites simultaneously by using tyrosine, tryptophan, and phenylalanine as "exploratory residues" to introduce steric hindrance or potential π-π interactions. The best variant Lk-S96Y/L199W identified with 17.2-fold improvement in catalytic efficiency could completely reduce up to 600 g/L (3.1 M) 2-chloro-1-(3,4-difluorophenyl)ethenone in 12 h with >99.5 % ee, giving the highest space-time yield ever reported. This study, therefore, offers a strategy for mutating alcohol dehydrogenase to reduce aromatic substrates and provides an efficient variant for the efficient synthesis of (S)-2-chloro-1-(3,4-difluorophenyl)ethanol.
Keywords: (S)-2-chloro-1-(3,4-difluorophenyl)ethanol; alcohol dehydrogenase; aromatic residue scanning; plasticity sites; protein engineering.
© 2023 Wiley-VCH GmbH.