A UDPGlc:flavonol O(3)-glucosyltransferase (EC 2.4.1.91) that catalyzes the formation of quercetin and kaempferol O(3)-glucosides has been purified about 1450-fold from illuminated red cabbage (Brassica oleracea cv Red Danish) seedlings with a 3.3% yield. Purification of the enzyme was achieved by