Characterization of Three Paris polyphylla Glycosyltransferases from Different UGT Families for Steroid Functionalization

Plant steroid glycosides, such as phytosterol glycosides, steroidal saponins, and steroidal glycoalkaloids, are natural products with great pharmaceutical values. In this study, we characterized three UDP-glycosyltransferases (UGTs) involved in the glycosylation of steroidal sapogenin from Paris polyphylla. Substrate specificity analysis revealed that UGT73CR1 could glycosylate steroidal sapogenins and steroidal alkaloids, with the highest affinity for diosgenin. The residues His27 and Asp129 of UGT73CR1 are conserved in corresponding positions of plant glycosyltransferases, which are crucial for activating the C-3 OH of the receptor substrates. In comparison, UGT80A33 and UGT80A34 exhibited a higher affinity for cholesterol than other steroids. UGT80s have a larger active pocket, which allows them to accommodate the side chain of sterols. In summary, we assessed three P. polyphylla glycosyltransferases from two UGT families for the functionalization of steroidal molecules, which will provide a basis for the future biomanufacturing of diverse bioactive steroid glycosides.