Catalyzes the transfer of the glucosyl moiety from UDP-glucose to the 5-hydroxyl group of anthocyanin. Anthocyanins are ubiquitous colored pigments that are responsible for variations in petal color. Also acts on the 3-O-rutinosides of pelargonidin, delphinidin and malvidin, but not the corresponding glucosides or 6-acylglucosides. Does not catalyze the glucosylation of the 5-hydroxy group of cyanidin 3-glucoside. cyanidin 3-O-rutinoside + UDP-alpha-D-glucose = cyanidin 3-O-rutinoside 5-O-beta-D-glucoside + H(+) + UDP Pigment biosynthesis; anthocyanin biosynthesis. Belongs to the UDP-glycosyltransferase family.