In situ UDP-glucose regeneration unravels diverse functions of plant secondary product glycosyltransferases.

The catalytic function of plant secondary product glycosyltransferases (PSPGs) was investigated by coupling the activities of recombinant flavonoid glucosyltransferases having different regiospecificities with sucrose synthase from Arabidopsis thaliana. In the present system, UDP, a product inhibitor of PSPGs, was removed from the reaction mixture and used for regeneration of UDP-glucose by AtSUS1. The in situ UDP-glucose regeneration system not only enhanced the glucosylation efficiency but also unraveled the novel regioselectivity of PSPGs. The effect of the system was shown to be because of the removal of UDP from the reaction system and not because of the additional supply of UDP-glucose.