Gallotannin biosynthesis:: Purification of β-glucogallin:: 1,2,3,4,6-pentagalloyl-β-D-glucose galloyltransferase from sumac leaves

An enzyme from leaves of staghorn sumac (Rhus typhina) that catalysed the galloylation of 1,2,3,4, 6-penta-O-galloyl-beta-D-glucose to the gallotannin, 3-O-digalloyl-1,2,4,6-tetra-O-galloyl-beta-D-glucose, was purified more than 500-fold to apparent homogeneity. beta-Glucogallin (1-O-galloyl-beta-D-glucopyranose) served as activated acyl donor in this conversion. For the native enzyme, a M(r) value of 170,000 was determined by gel filtration, while a single polypeptide band of M(r) 42,000 was detected by SDS-PAGE. The acyltransferase had pH and temperature optima of 4-4.5 and 25 degrees, respectively, and was most stable between pH 3 and 4.5. Besides the major substrate, pentagalloylglucose, also 1,2,3,6-tetragalloylglucose and hexa- to nona-substituted gallotannins were accepted as minor substrates by this new enzyme for which the systematic name "beta-glucogallin: 1,2,3,4,6-pentagalloyl-beta-D-glucose (3-O-galloyl)-galloyltransferase" (EC 2.3.1.-) is proposed. (C) 1998 Elsevier Science Ltd. All rights reserved.