Comparative Analysis of Catalytic Properties and Mechanisms between HvUGT13248 and OsUGT79 in Deoxynivalenol Glycosylation

HvUGT13248 and OsUGT79 are homologous glycosyltransferases for deoxynivalenol (DON) glycosylation with limited efficiency. Their distinct features and the underlying catalytic mechanism remain poorly understood. Here, comparative analysis demonstrated that HvUGT13248 exhibited higher catalytic efficiency toward DON and its analogs but was constrained by relatively lower yield and poor stability in practical application. In contrast, OsUGT79 achieved complete conversion under excess donor due to its enhanced resistance to feedback inhibition of UDP and robust thermal stability. Three key active-site residues were identified, and their functional roles were evaluated comparatively. Among these, His38/27 was essential for glycosylation by both HvUGT13248 and OsUGT79. Interaction between His132/His122 and the C4, C7, and C15 positions of DON provided a structural rationale for their differential activities toward C4-substituted trichothecenes. Furthermore, Asp393 played a more critical role in stabilizing the enzyme-substrate complex in HvUGT13248. These findings advance the engineering of both enzymes for improved DON glycosylation.