Characterization of UDP-Glycosyltransferase Involved in Biosynthesis of Ginsenosides Rg1 and Rb1 and Identification of Critical Conserved Amino Acid Residues for Its Function

Ginsenosides attract great attention for their bioactivities. However, their contents are low, and many UDP-glycosyltransferases (UGTs) that play crucial roles in the ginsenoside biosynthesis pathways have not been identified, which hinders the biosynthesis of ginsenosides. In this study, we reported that one UDP-glycosyltransferase, UGTPg71A29, from Panax ginseng could glycosylate C20-OH of Rh₁ and transfer a glucose moiety to Rd, producing ginsenosides Rg₁ and Rb₁, respectively. Ectopic expression of UGTPg71A29 in Saccharomyces cerevisiae stably generated Rg₁ and Rb₁ under its corresponding substrate. Overexpression of UGTPg71A29 in transgenic cells of P. ginseng could significantly enhance the accumulation of Rg₁ and Rb₁, with their contents of 3.2- and 3.5-fold higher than those in the control, respectively. Homology modeling, molecular dynamics, and mutational analysis revealed the key catalytic site, Gln283, which provided insights into the catalytic mechanism of UGTPg71A29. These results not only provide an efficient enzymatic tool for the synthesis of glycosides but also help achieve large-scale industrial production of glycosides.