Synthesis of β‐glucogallin from UDP‐glucose and gallic acid by an enzyme preparation from oak leaves

Cell‐free extracts from oak leaves were found to catalyze the esterification of 14C‐labeled gallic acid and UDP‐glucose. The product of the enzymatic reaction was identified as β‐glucogallin by means of TLC and HPLC. The reaction proceded linearly with respect to time and protein concentration and had a pH‐optimum at 7.0. Normal Michaelis‐Menten kinetics were observed for the substrates gallic acid (K M = 1.1 mM) and UDP‐glucose (2.3 mM). The new enzyme described here can be classified as UDP‐glucose: gallate glucosyltransferase, and it is assumed that it catalyzes the first step in the biosynthesis of gallotannins.