In the presence of other necessary color factors, this glycosylation reaction allows the accumulation of anthocyanin pigments (Probable). Involved in the formation of red wine pigments (Probable). UDP-glucose (UDP-Glc) is the physiological sugar donor, and cyanidin is the natural acceptor in vivo (PubMed:9535914). Can glucosylate the anthocyanidins delphinidin, peonidin, pelargonidin and malvidin (PubMed:9535914). The flavonols quercitin and kaempferol can also be glucosylated in vitro, but with glucosylation rates 50-100 times lower than cyanidin (PubMed:9535914). In vitro, can use UDP-Glc, UDP-5SGlc, UDP-Xyl, UDP-Man, UDP-Gal, UDP-GlcNAc, GDP-Glc, dTDP-Glc and dTDP-Xyl as sugar donors, but not UDP-6OMeGal, UDP-Ara, UDP-6FGal, UDP-GlcN, UDP-2FGal, UDP-5SAra, GDP-Man, GDP-Fuc, UDP-Fuc or UDP-Rha (PubMed:16482224). an anthocyanidin + H(+) + UDP-alpha-D-glucose = an anthocyanidin 3-O-beta-D-glucoside + UDP cyanidin + UDP-alpha-D-glucose = cyanidin 3-O-beta-D-glucoside + H(+) + UDP delphinidin + UDP-alpha-D-glucose = delphinidin 3-O-beta-D-glucoside + UDP peonidin + UDP-alpha-D-glucose = peonidin 3-O-beta-D-glucoside + UDP pelargonidin + UDP-alpha-D-glucose = pelargonidin 3-O-beta-D-glucoside + UDP malvidin + UDP-alpha-D-glucose = malvidin 3-O-beta-D-glucoside + UDP a flavonol + UDP-alpha-D-glucose = a flavonol 3-O-beta-D-glucoside + H(+) + UDP Inhibited by Mn(2+) and Zn(2+). Optimum pH is 8.0. Pigment biosynthesis; anthocyanin biosynthesis. Detected only in berry skin. By light. The expression of UFGT is not detected in white grapes. Belongs to the UDP-glycosyltransferase family.