Semi-rational design of carbonyl reductase Cat for synthesis of (R)-lipoic acid precursor

(R)-ethyl-8-chloro-6-hydroxyoctanoate is an important intermediate in the synthesis of (R)-α-lipoic acid. For efficient biosynthesis, carbonyl reductase Cat from Candida theae was designed using semi-rational design strategy to reduce ethyl 8-chloro-6-oxooctanoate asymmetrically. After four rounds of design, mutant CatS126A/R129Q/V194A with a significant increase in catalytic efficiency and enantioselectivity was obtained. The molecular dynamics simulation results demonstrated that the expanded substrate binding pocket and the more reasonable interaction between CatS126A/R129Q/V194A and substrate or cofactor were the main reasons for the enhanced catalytic performance. In addition, ethyl 8-chloro-6-oxooctanoate (220 g∙L−1) could be effectively reduced using broken cells within 5 h, with a yield of 98% and ee value of 98%. The space-time yield was 696 g∙L−1 ∙d−1. These results suggested CatS126A/R129Q/V194A was a potential biocatalyst for green production of (R)-ethyl-8-chloro-6-hydroxyoctanoate at the industrial sale.