Catalytic performance of a highly enantioselective ( R)-ester hydrolase from a new isolate Acinetobacter sp. CGMCC 0789

Abstract

A highly enantioselective ( R)-ester hydrolase was partially purified from a newly isolated bacterium, Acinetobacter sp. CGMCC 0789, whose resting cells exhibited a highly enantioselective activity toward the acetate of (4 R)-hydroxy-3-methyl-2-(2-propynyl)- cyclopent-2-enone ( R-HMPC). The optimum pH and temperature of the partially purified enzyme were 8.0 and 60 °C, respectively. The enantioselectivity of the crude enzyme was increased by 1.2-fold from 16 to 20 when the reaction temperature was raised from 30 to 60 °C. The activity of the crude enzyme was enhanced by 4.1-fold and the enantioselectivity ( E-value) was markedly enhanced by 4.3-fold from 16 to 68 upon addition of a cationic detergent, benzethonium chloride [(diisobutyl phenoxyethoxyethyl) dimethyl benzylammoniom chloride]. The hydrolysis of 52 mM ( R, S)-HMPC acetate to ( R)-HMPC was completed within 8 h, with optical purity of 91.4% ee p and conversion of 49%.