Cloning and expression of a NAD+-dependent xylitol dehydrogenase gene (xdhA) of Aspergillus oryzae

XdhA, which encodes a xylitol dehydrogenase gene, was cloned from Aspergillus oryzae genomic DNA. It consists of 1214 bp structural region, which is interrupted by two introns, and encodes 358-amino-acid protein (38,197 Da). It is similar to the known NAD+-dependent xylitol dehydrogenase (EC 1.1.1.9). The gene was expressed in Escherichia coli BL21-AI using a T7 promoter. The cell-free extract of the transformant showed a 36.5 kDa band upon SDS–PAGE and NAD+-dependent xylitol dehydrogenase activity.