A muti-substrate flavonol O-glucosyltransferases from safflower

Abstract

Abstract A glycosyltransferase CtUGT4 with flavonoid-O-glycosyltransferase activity was identified in safflower. The fusion protein of CtUGT4 was heterologously expressed in Escherichia coli, and the target protein was purified. The recombinant protein can catalyze quercetin to form quercetin-7-O-glucoside and kaempferol to form kaempferol-3-O in vitro, and a series of flavones, flavonols, dihydroflavones, chalcones, and chalcone glycosides were used as substrates to generate new products. CtUGT4 was expressed in the tobacco transient expression system, and the enzyme activity results showed that it could catalyze kaempferol to kaempferol-3-O-glucoside, and quercetin to quercetin-7-O-glucoside. After overexpressing CtUGT4 in safflower, the content of quercetin-3-O-rutinoside in the florets of safflower increased significantly, and the content of quercetin-3-O-glucoside also tended to increase, which preliminarily proved the function of CtUGT4 flavonoid-O-glycosyltransferase. This work demonstrated the flavonoid-O-glycosyltransferase function of safflower CtUGT4 and showed differences in affinity for different flavonoid substrates and regioselectivity of catalytic sites in safflower in vivo and in vitro, which provides clues for further research on the function of UGT genes and new ideas for the cultivation engineering of directional improvement of effective metabolites in safflower.