Title Cloning, Expression, and Characterization of Xylose Reductase with Higher Activity from Candida tropicalis
Author Feiwei Zhang1, Dairong Qiao1,2, Hui Xu1, Chong Liao1, Shilin Li1, and Yi Cao1,2*
Address 1College of Life Sciences, Sichuan University, Chengdu 610064, P. R. China, 2Sichuan Public Experimental Platform of Bioinformatics and Metabolic Engineering, Chengdu 610064, P. R. China
Bibliography Journal of Microbiology, 47(3),351-357, 2009,
Key Words Candida tropicalis, xylose reductase, coenzyme specificity, catalytic efficiency
Abstract Xylose reductase (XR) is a key enzyme in xylose metabolism because it catalyzes the reduction of xylose to xylitol. In order to study the characteristics of XR from Candida tropicalis SCTCC 300249, its XR gene(xyl1) was cloned and expressed in Escherichia coli BL21 (DE3). The fusion protein was purified effectively by Ni2+-chelating chromatography, and the kinetics of the recombinant XR was investigated. The Km values of the C. tropicalis XR for NADPH and NADH were 45.5 uM and 161.9 uM, respectively, which demonstrated that this XR had dual coenzyme specificity. Moreover, this XR showed the highest catalytic efficiency (kcat=1.44x04 min-1) for xylose among the characterized aldose reductases. Batch fermentation was performed with Saccharomyces serivisiae W303-1A:pYES2XR, and resulted in 7.63 g/L cell mass, 93.67 g/L xylitol, and 2.34 g/Lh xylitol productivity. This XR coupled with its dual coenzyme specificity, high activity, and catalytic efficiency proved its utility in in vitro xylitol production.