In the presence of other necessary color factors, this glycosylation reaction allows the accumulation of anthocyanin pigments (Probable). Uses UDP-Glc as a sugar donor, but not UDP-Gal or UDP-GlcUA (PubMed:18258692). Anthocyanidins are the preferred substrates in vivo, but flavonols can also be glucosylated in vitro (PubMed:18258692). 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 pelargonidin + UDP-alpha-D-glucose = pelargonidin 3-O-beta-D-glucoside + UDP peonidin + UDP-alpha-D-glucose = peonidin 3-O-beta-D-glucoside + UDP delphinidin + UDP-alpha-D-glucose = delphinidin 3-O-beta-D-glucoside + UDP a flavonol + UDP-alpha-D-glucose = a flavonol 3-O-beta-D-glucoside + H(+) + UDP The kinetic constants are determined for the recombinant His(6)-tagged protein. Optimum pH is 7-8 with pelargonidin and cyanidin as substrates. Optimum temperature is 30 degrees Celsius with pelargonidin and cyanidin as substrates. Pigment biosynthesis; anthocyanin biosynthesis. Highest expression detected in receptacles and achenes, with very low levels detected in runners, leaves, flowers, crowns and green receptacles. Expression in achenes and receptacles is ripening-related, with highest expression levels detected in fully ripe red receptacles. By de-achening. Down-regulated by synthetic auxin naphthaleneacetic acid (NAA). Belongs to the UDP-glycosyltransferase family.