pH-rate profiles of l-arabinitol 4-dehydrogenase from Hypocrea jecorina and its application in l-xylulose production

l-Arabinitol 4-dehydrogenase (LAD) from Hypocrea jecorina (HjLAD) was cloned and overexpressed in Escherichia coli BL21 (DE3). The kinetics of l-arabinitol oxidation by NAD+, catalyzed by HjLAD, was studied within the pH range of 7.0-9.5 at 25 °C. The turnover number (kcat) and the catalytic efficiency (kcat/Km) were 4200 min−1 and 290 mM−1 min−1, respectively. HjLAD showed the highest turnover number and catalytic efficiency among all previously characterized LADs. In further application of HjLAD, rare l-sugar l-xylulose was produced by the enzymatic oxidation of arabinitol to give a yield of approximately 86%.