title: Gallotannin biosynthesis: two new galloyltransferases from Rhus typhina leaves preferentially acylating hexa- and heptagalloylglucoses.
abstract: Current enzyme studies on the biosynthesis of gallotannins with cell-free extracts from leaves of staghorn sumac (Rhus typhina L.) revealed the existence of two new beta-glucogallin-dependent galloyltransferases (EC 2.3.1.-) that preferentially catalyzed the acylation of hexa- and heptagalloylglucoses. One enzyme was most active with the hexagalloylglucose, 3-O-digalloyl-1,2,4,6-tetra-O-galloylglucose, to form the corresponding heptagalloylglucose, 3-O-trigalloyl-1,2,4,6-tetra-O-galloylglucose. This polyester, in turn, was the preferred substrate for a second enzyme that catalyzed its conversion to higher substituted derivatives. This latter enzyme also displayed considerable affinity towards 2-O-digalloyl-1,3,4,6-tetra-O-galloylglucose which was acylated to various hepta- and octagalloylglucoses. These recent findings, together with data from earlier reported related enzymes, allowed the presentation of a scheme that summarizes the major transitions in the biogenetic routes from 1,2,3,4,6-pentagalloylglucose to complex gallotannins.
authors.affiliation: Molekulare Botanik, Universität Ulm, 89069 Ulm, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Fröhlich
authors.forename: Ruth
authors.initials: R
authors.lastname: Niemetz
authors.forename: Georg G
authors.initials: GG
authors.lastname: Gross
mesh_terms: D000215:Acylation; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D005960:Glucosides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D047348:Hydrolyzable Tannins / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D018515:Plant Leaves / Q000201:enzymology*; D029045:Rhus / Q000201:enzymology*; D013379:Substrate Specificity; D013634:Tannins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D014166:Transferases / Q000302:isolation & purification / Q000378:metabolism
chemical_list: C472379:2-O-digalloyl-1,3,4,6-tetra-O-galloylglucose; C409902:3-O-digalloyl-1,2,4,6-tetra-O-galloylglucose; D005960:Glucosides; D047348:Hydrolyzable Tannins; D013634:Tannins; C435084:pentagalloylglucose; C060474:glucogallin; D005707:Gallic Acid; D014166:Transferases