Structure-function relationships in plant UDP-glycosyltransferases

Uridine diphosphate-dependent glycosyltransferases (UGTs) in plants catalyze O-, C-, S- and N-glycosylation of diverse substrates to yield a wide variety of glycosides with broad bioactivities. Not all wild-type plant UGTs can exhibit excellent catalytic characteristics and achieve application requirements. Desirable enzymes with far greater catalytic properties than the wild type can be obtained through enzyme engineering. Here, we enumerate all currently resolved crystal structures of plant UGTs. The proposed mechanisms for the four types of glycosylation are then summarized. Structure-based protein engineering strategies for improving the catalytic properties of plant UGTs and their principles are further elaborated. Finally, aspects that need in-depth studies and trends for future application of plant UGTs are discussed.