title: Identification of UGT84A13 as a candidate enzyme for the first committed step of gallotannin biosynthesis in pedunculate oak (Quercus robur).
abstract: A cDNA encoding the ester-forming hydroxybenzoic acid glucosyltransferase UGT84A13 was isolated from a cDNA library of Quercus robur swelling buds and young leaves. The enzyme displayed high sequence identity to resveratrol/hydroxycinnamate and hydroxybenzoate/hydroxycinnamate glucosyltransferases from Vitis species and clustered to the phylogenetic group L of plant glucosyltransferases, mainly involved in the formation of 1-O-β-D-glucose esters. In silico transcriptome analysis confirmed expression of UGT84A13 in Quercus tissues which were previously shown to exhibit UDP-glucose:gallic acid glucosyltransferase activity. UGT84A13 was functionally expressed in Escherichia coli as N-terminal His-tagged protein. In vitro kinetic measurements with the purified recombinant enzyme revealed a clear preference for hydroxybenzoic acids as glucosyl acceptor in comparison to hydroxycinnamic acids. Of the preferred in vitro substrates, protocatechuic, vanillic and gallic acid, only the latter and its corresponding 1-O-ß-D-glucose ester were found to be accumulated in young oak leaves. This indicates that in planta UGT84A13 catalyzes the formation of , 1-O-galloyl-ß-D-glucose, the first committed step of gallotannin biosynthesis.
authors.affiliation: Interdisciplinary Center for Crop Plant Research, Martin-Luther University Halle-Wittenberg, Hoher Weg 8, D-06120 Halle, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Mittasch
authors.affiliation: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Böttcher
authors.affiliation: Interdisciplinary Center for Crop Plant Research, Martin-Luther University Halle-Wittenberg, Hoher Weg 8, D-06120 Halle, Germany.
authors.forename: Nadezhda
authors.initials: N
authors.lastname: Frolova
authors.affiliation: UFZ - Helmholtz Centre for Environmental Research, Department of Soil Ecology, Theodor-Lieser-Str. 4, 06120 Halle, Germany; Institute of Computer Science, Martin-Luther University Halle-Wittenberg, Von-Seckendorff-Platz 1, 06120 Halle, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Bönn
authors.affiliation: Interdisciplinary Center for Crop Plant Research, Martin-Luther University Halle-Wittenberg, Hoher Weg 8, D-06120 Halle, Germany. Electronic address: carsten.milkowski@izn.uni-halle.de.
authors.forename: Carsten
authors.initials: C
authors.lastname: Milkowski
mesh_terms: D005964:Glucosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D047348:Hydrolyzable Tannins / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D018515:Plant Leaves / Q000201:enzymology; D018520:Plant Shoots / Q000201:enzymology; D029963:Quercus / Q000201:enzymology* / Q000378:metabolism
chemical_list: D047348:Hydrolyzable Tannins; D005964:Glucosyltransferases
keywords: Fagaceae; Gallotannins; Glucosyltransferase; Quercus robur; Substrate specificity