Catalytic flexibility of rice glycosyltransferase OsUGT91C1 for the production of palatable steviol glycosides

Steviol glycosides, intensely sweet components from *Stevia rebaudiana*, are potential low-calorie sweeteners. Reb D and Reb M, desirable for their lack of aftertaste, are naturally scarce. This study characterizes OsUGT91C1, a rice glycosyltransferase efficiently catalyzing β(1→2) glucosylation crucial for Reb D and Reb M synthesis. OsUGT91C1's flexibility stems from three substrate-binding modes, enabling β(1→2) glucosylation in two orientations and β(1→6) glucosylation. Engineered OsUGT91C1 variants enhance desired β(1→2) glucosylation, eliminate unwanted β(1→6) glucosylation, promising improved Reb D and Reb M production.

Jinzhu Zhang, Minghai Tang, Yujie Chen, Dan Ke, Jie Zhou, Xinyu Xu, Wenxian Yang, Jianxiong He, Haohao Dong, Yuquan Wei, James H. Naismith, Yi Lin, Xiaofeng Zhu, Wei Cheng