A novel carboxylesterase from Acinetobacter sp. JNU9335 for efficient biosynthesis of Edoxaban precursor with high substrate to catalyst ratio

A novel carboxylesterase AcEst1 was identified from Acinetobacter sp. JNU9335 with high efficiency in the biosynthesis of chiral precursor of Edoxaban through kinetic resolution of methyl 3-cyclohexene-1-carboxylate (CHCM). Sequence analysis revealed AcEst1 belongs to family IV of esterolytic enzymes and exhibits <40% identities with known carboxylesterases. The optimum pH and temperature of recombinant AcEst1 are 8.0 and 40 °C. Substrate spectrum analysis indicated that AcEst1 prefers substrates with short acyl and alcohol groups. AcEst1 was highly active in the hydrolysis of CHCM with kcat of 1153 s-1 and displayed high substrate tolerance. As much as 2.0 M (280 g·L-1) CHCM could be enantioselectively hydrolyzed into (S)-CHCM by merely 0.08 g·L-1AcEst1 with ees of >99% (S) and substrate to catalyst ratio (S/C) of 3500 g·g-1. These results indicate that the novel AcEst1 is a promising biocatalyst in the synthesis of chiral carboxylic acids.