earticle

영어

Xylose reductase (XR) is a key enzyme in D-xylose metabolism, catalyzing the reduction of D-xylose to xylitol. However, the broad substrate spectrum of XR can also reduce L-arabinose to L-arabitol, byproduct, which requires expensive downstream process in industrial xylitol production. Some filamentous fungi have L-arabitol dehydrogenase(LAD) oxidizing L-arabitol to L-xylulose and Lxylulose reductase(LXR) reducing L-xylulose to xylitol. Genes incoding LAD and LXR were isolated from the genomic DNA of Neurospora crassa ATCC10333. Each gene was expressed in Escherichia coli BL21(DE3) using T7 promoter. Expression of LAD and LXR was confirmed by determining enzyme activity in cells grown on the LB media. The activity of LAD and LXR was 600 mU/mg of proteins and 4430 mU/mg of proteins, respectively. In vitro assay was performed for conversion of arabitol to xylitol using crude enzymes(LAD and LXR) and cofactors(NAD and NADPH). Substrates and products were analyzed by HPLC, and consequently, 49% of arabitol was converted to xylitol for two hours of enzyme reaction.