Characterization of a (2R,3R)-2,3-butanediol dehydrogenase from Rhodococcus erythropolis WZ010

Abstract

The gene encoding a (2R,3R)-2,3-butanediol dehydrogenase from Rhodococcus erythropolis WZ010 (ReBDH) was over-expressed in Escherichia coli and the resulting recombinant ReBDH was successfully purified by Ni-affinity chromatography. The purified ReBDH in the native form was found to exist as a monomer with a calculated subunit size of 37180, belonging to the family of the zinc-containing alcohol dehydrogenases. The enzyme was NAD(H)-specific and its optimal activity for acetoin reduction was observed at pH 6.5 and 55°C. The optimal pH and temperature for 2,3-butanediol oxidation were pH 10 and 45°C, respectively. The enzyme activity was inhibited by ethylenediaminetetraacetic acid (EDTA) or metal ions Al 3+, Zn 2+, Fe 2+, Cu 2+ and A g+, while the addition of 10% (v/v) dimethyl sulfoxide (DMSO) in the reaction mixture increased the activity by 161.2%. Kinetic parameters of the enzyme showed lower K m values and higher catalytic efficiency for diacetyl and NADH in comparison to those for (2R,3R)-2,3-butanediol and NAD +. The activity of acetoin reduction was 7.7 times higher than that of (2R,3R)-2,3-butanediol oxidation when ReBDH was assayed at pH 7.0, suggesting that ReBDH-catalyzed reaction in vivo might favor (2R,3R)-2,3-butanediol formation rather than (2R,3R)-2,3-butanediol oxidation. The enzyme displayed absolute stereospecificity in the reduction of diacetyl to (2R,3R)-2,3-butanediol via (R)-acetoin, demonstrating its potential application on the synthesis of (R)-chiral alcohols.