Identification and characterization of three flavonoid 3-O-glycosyltransferases from Epimedium koreanum Nakai

Glycosylation of flavonoids is one of the most important modifications in flavonoid biosynthesis pathways, which contributes to the biochemical activity as well as the solubility of flavonoids. However, reports on glycosyltransferases that catalyze specifically the 3-O-glycosylation of flavonoids are limited. In the current work, three novel flavonoid 3-O-glycosyltransferases as well as one UDP-rhamnose synthase were identified and functionally characterized using RNA sequencing from Epimedium koreanum Nakai. These glycosyltransferases were found to catalyze the glucosylation, galactosylation and rhamnosylation of several flavonoids specifically at the 3-OH position. Phylogenetic analysis of the three glycosyltransferases showed that they all belonged to the 3 G T family. According to the results, the three newly identified glycosyltransferases from Epimedium exhibited glycosylation activity especially toward prenylated flavonoids which has never been reported before. The bioconversion experiment with engineered yeasts expressing the three glycosyltransferases showed great application potential in glycosylation of flavonoids. All these studies contributed to a better understanding of flavonoid 3-O-glycosyltransferases from Epimedium and will promote the biosynthesis of different kinds of bioactive flavonoid glycosides with synthetic biology methods.