Discovery and Biochemical Characterization of UDP-Glucose Dehydrogenase from Granulibacter bethesdensis.

UDP-glucose dehydrogenases (EC 1.1.1.22) are responsible for the conversion of UDP-glucose to UDP-glucuronic acid, a key precursor in the biosynthesis of glycoconjugates. Herein we report the discovery and characterization of a UDPglucose dehydrogenase (GbUGD) from Granulibacter bethesdensis, a bacterium originally isolated from the lymph nodes of patients with chronic granulomatous disease (CGD). The recombinant form of the protein was expressed in high yield and the purified enzyme showed highest activity at 37°C/pH 9.0 and was strongly inhibited by Zn(2+) ions, sodium dodecyl sulfate (SDS) and urea. UDP-xylose, an allosteric feedback inhibitor, reduced significantly the activity of the enzyme. High activities were observed using the co-substrates UDP-glucose and NAD+, whereas no activity could be detected using other nucleotide sugars or NADP(+) as potential alternative substrates. The high activity combined with the simple purification procedure used make GbUGD a valuable new alternative biocatalyst for the synthesis of UDP-glucuronic acid or the development of NAD+ regeneration systems.