Enantioselectivities of Uridine Diphosphate-Glucose:Monoterpenol Glucosyltransferases from Grapevine (Vitis vinifera L.)

Aroma-active substances, like monoterpene alcohols, often occur as non-aromatic, glycosidically bound forms and accumulate during grape ripening. Although these compounds are a precious source of aroma, little is known about the enzymes catalyzing this glycosylation. Recently, heterologous expression and biochemical assays of candidate genes extracted from the V. vinifera (Vv) genome database has led to the identification of several UDP-glucose:monoterpenol β-D-glucosyltransferases (UDP-Glc GTs). Here, kinetic resolution of racemic monoterpenols is demonstrated for several of these GTs. Thus, the enantioselective "aroma-hiding" biochemistry of these enzymes is shown for the first time in grapevine.