Synthesis of Mono-, Di-and Trigalloyl-β-ᴅ-glucose by β-Glucogallin-Dependent Galloyltransferases from Oak Leaves

Abstract

Cell-free extracts from oak (Quercus robur) leaves were found to contain at least two β-glucogallin-dependent galloyltransferases. One enzyme catalyzed a rapid exchange of the galloylmoiety of β-glucogallin with free glucose. A second enzyme fraction was shown to form digalloylglucose, utilizing β-glucogallin both as acyl-donor and acceptor molecule; in addition, evidence for the synthesis of trigalloylglucose was obtained. Both enzyme-systems had their pH-optimum at pH 6.0-6.5. It is assumed that these newly described galloyltransferases are involved in the biosynthesis of gallotannins.