Preparation of Structurally Diverse Chiral Alcohols by Engineering Ketoreductase CgKR1

Ketoreductases are tools for the synthesis of chiral alcohols in industry. However, the low activity of natural enzymes often restricts their use in industrial applications. On the basis of computational analysis and previous reports, two residues (F92 and F94) probably affecting the activity of ketoreductase CgKR1 were identified. By tuning these two residues, the CgKR1-F92C/F94W variant was obtained that exhibited higher activity toward all 28 structurally diverse substrates examined than the wild-type enzyme. Among them, 13 substrates have a specific activity over 50 U mg(-1) (54-775 U mg(-1)). Using CgKR1-F92C/F94W as a catalyst, five substrates at high loading (>100 g(-1) L-1) were reduced completely in gram scale preparative reactions. This approach provides accesses to pharmaceutically relevant chiral alcohols with high enantioselectivity (up to 99.0% ee) and high space-time yield (up to 583 g(-1) L-1 day(-1)). Molecular dynamics simulations highlighted the crucial role of residues 92 and 94 in activity improvement. Our findings provide useful guidance for engineering other ketoreductases, especially those possessing a similar active pocket to that in CgKR1.