A novel NADH-dependent carbonyl reductase with unusual stereoselectivity for (R)-specific reduction from an (S)-1-phenyl-1,2-ethanediol-producing micro-organism: purification and characterization.

Y Nie, Y Xu, M Yang, X-Q Mu

Index: Lett. Appl. Microbiol. 44(5) , 555-62, (2007)

Full Text: HTML

Abstract

To purify and characterize the (R)-specific carbonyl reductase from Candida parapsilosis; to compare the enzyme with other stereospecific oxidoreductases; and to develop an available procedure producing optically active (R)-1-phenyl-1,2-ethanediol (PED).An (R)-specific carbonyl reductase was found and purified from C. parapsilosis through four steps, including blue-sepharose affinity chromatography. The relative molecular mass of the enzyme was estimated to be 35 kDa on gel-filtration chromatography and 37.5 kDa on Sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme catalysed the reduction of various ketones, including alkyl and aromatic ketones, and was specific to short-chain and medium-chain alkyl ketones. The enzyme activity was inhibited by divalent ion of CuSO(4) and FeSO(4), whereas zincum ion stimulated its activity. For catalysing reduction, the enzyme performed maximum activity at pH 6.0 and the optimum temperature was 45 degrees C. The carbonyl reductase catalysed asymmetric reduction of beta-hydroxyacetophenone to the corresponding (R)-PED with the optical purity of 100% enantiomeric excess (e.e.). By analysing its partial amino acid sequences, the enzyme was proposed to be a novel stereospecific carbonyl reductase.The purified carbonyl reductase showed unusual stereospecificity and catalysed the NADH-dependent reduction of beta-hydroxyacetophenone to (R)-PED. The enzyme was different from other stereoselective oxidoreductases in catalytic properties.The discovery of (R)-specific oxidoreductase exhibiting unusual stereospecificity towards hydroxyl ketone is valuable for the synthesis of both enantiomers of useful chiral alcohols, and provides research basis for the achievement of profound knowledge on the relationship between structure and catalytic function of (R)-specific enzymes, which is meaningful for the alteration of stereospecificity by molecular methods to obtain the enzymes with desired stereospecificity.