Molecular cloning and biochemical characterization of the UDP-glucose: Flavonoid 3-O-glucosyltransferase from Concord grape (Vitis labrusca)

► Molecular and biochemical characterization grape berry anthocyanidin 3-O-glucosyltransferase. ► Enzyme shows its strict regiospecificity for the 3-O-position of anthocyanidins and flavonols. ► Enzyme uses of UDP-glucose, but not UDP-galactose as a donor substrate. ► Kinetic analysis to show that rVL3GT preferentially glucosylates anthocyanidins in vitro. ► Gene expression coincides with post-veraison appearance of anthocyanidin 3GT enzyme activity.