Directed Evolution of the UDP-Glycosyltransferase UGT BL 1 for Highly Regioselective and Efficient Biosynthesis of Natural Phenolic Glycosides.

The O-glycosylation of polyphenols for the synthesis of glycosides has garnered substantial attention in food research applications. However, the practical utility of UDP-glycosyltransferases (UGTs) is significantly hindered by their low catalytic efficiency and suboptimal regioselectivity. The concurrent optimization of the regioselectivity and activity during the glycosylation of polyphenols presents a formidable challenge. Here, we addressed the long-standing activity-regioselectivity tradeoff in glycosyltransferase UGT BL 1 through systematic enzyme engineering. The optimal combination of mutants, N61S/I62M/D63W/A208R/P218W/R282W (SMWRW 1 W 2 ), yielded a 6.1-fold improvement in relative activity and a 17.3-fold increase in the ratio of gastrodin to para -hydroxybenzyl alcohol-4'- O -β-glucoside (with 89.5% regioselectivity for gastrodin) compared to those of the wild-type enzyme and ultimately allowed gram-scale production of gastrodin (1,066.2 mg/L) using whole-cell biocatalysis. In addition, variant SMWRW 1 W 2 exhibited a preference for producing phenolic glycosides from several substrates. This study lays the foundation for the engineering of additional UGTs and the practical applications of UGTs in regioselective retrofitting.