Recombinant UDP-glucose dehydrogenase from soybean

The enzyme UDP-glucose dehydrogenase (UDP-GlcDH, EC 1.1.1.22) converts the nucleotide sugar UDP-glucose (UDP-Glc) into UDP-glucuronic acid (UDP-GlcA), precursor for many sugars in pectins, xyloglucans or arabinose-containing polymers. We have developed a method to produce high amounts of soluble recombinant UDP-GlcDH. The analysis of the substrate specificity indicates that only UDP-Glc but not UDP-galactose is converted into the corresponding uronic acid by the UDP-GlcDH. The K-m value for UDP-Glc was calculated to 22 and 70 muM for NAD(+), respectively. The soybean (Glycine max (L.) Merrill) enzyme is inhibited in a competitive manner by UDP-xylose with a K-i value of 10 muM, suggesting a feedback control of the production of sugar nucleotides used for the synthesis of plant cell walls. In contrast to the UDP-GlcDH from bovine, which is only active as a hexameric complex, the soybean enzyme catalyses the reaction as a monomer. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.