Extending the Structural Diversity of α-Flavonoid Glycosides with Engineered Glucansucrases

Flavonoids constitute an important class of bioactive molecules, the physicochemical properties of which can be modulated by glucosylation. A structurally guided approach has been used to isolate glucansucrases modified in their acceptor-binding site and specialized for luteolin glucosylation. Of a small-size library, we isolate mutants showing up to an 8-fold increase in flavonoid conversion rate over that observed with the parental enzyme. Di- and triglucosylated luteolin derivatives never described before have been obtained. They exhibit 282- and 17708-fold increases in water solubility, respectively, and are protected from oxidation by the glucosylation reaction. Molecular docking enables insight into the product specificity of the best mutants. These results demonstrate that atransglucosylase engineering is a powerful means to generate highly specific catalysts for flavonoid glucosylation and deliver new structural scaffolds with increased bioavailability and high relevance for therapeutic applications.