title: Formation of β-glucogallin, the precursor of ellagic acid in strawberry and raspberry.
abstract: Ellagic acid/ellagitannins are plant polyphenolic antioxidants that are synthesized from gallic acid and have been associated with a reduced risk of cancer and cardiovascular diseases. Here, we report the identification and characterization of five glycosyltransferases (GTs) from two genera of the Rosaceae family (Fragaria and Rubus; F. × ananassa FaGT2*, FaGT2, FaGT5, F. vesca FvGT2, and R. idaeus RiGT2) that catalyze the formation of 1-O-galloyl-β-D-glucopyranose (β-glucogallin) the precursor of ellagitannin biosynthesis. The enzymes showed substrate promiscuity as they formed glucose esters of a variety of (hydroxyl)benzoic and (hydroxyl)cinnamic acids. Determination of kinetic values and site-directed mutagenesis revealed amino acids that affected substrate preference and catalytic activity. Green immature strawberry fruits were identified as the main source of gallic acid, β-glucogallin, and ellagic acid in accordance with the highest GT2 gene expression levels. Injection of isotopically labeled gallic acid into green fruits of stable transgenic antisense FaGT2 strawberry plants clearly confirmed the in planta function. Our results indicate that GT2 enzymes might contribute to the production of ellagic acid/ellagitannins in strawberry and raspberry, and are useful to develop strawberry fruit with additional health benefits and for the biotechnological production of bioactive polyphenols.
authors.affiliation: Biotechnology of Natural Products, Technische Univeristät München, Liesel-Beckmann-Str. 1, D-85354 Freising, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Schulenburg
authors.affiliation: Department of Food Quality and Nutrition, IASMA Research and Innovation Center, Fondazione Edmund Mach (FEM), Via E. Mach 1, 38010 San Michele all'Adige, (TN), Italy.
authors.forename: Antje
authors.initials: A
authors.lastname: Feller
authors.affiliation: Biotechnology of Natural Products, Technische Univeristät München, Liesel-Beckmann-Str. 1, D-85354 Freising, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoffmann
authors.affiliation: Biotechnology of Natural Products, Technische Univeristät München, Liesel-Beckmann-Str. 1, D-85354 Freising, Germany.
authors.forename: Johannes H
authors.initials: JH
authors.lastname: Schecker
authors.affiliation: Department of Food Quality and Nutrition, IASMA Research and Innovation Center, Fondazione Edmund Mach (FEM), Via E. Mach 1, 38010 San Michele all'Adige, (TN), Italy.
authors.forename: Stefan
authors.initials: S
authors.lastname: Martens
authors.affiliation: Biotechnology of Natural Products, Technische Univeristät München, Liesel-Beckmann-Str. 1, D-85354 Freising, Germany Wilfried.Schwab@tum.de.
authors.forename: Wilfried
authors.identifier: http://orcid.org/0000-0002-9753-3967
authors.initials: W
authors.lastname: Schwab
mesh_terms: D000595:Amino Acid Sequence; D004610:Ellagic Acid / Q000737:chemistry / Q000378:metabolism*; D031985:Fragaria / Q000378:metabolism*; D016695:Glycosyltransferases / Q000737:chemistry / Q000378:metabolism; D047348:Hydrolyzable Tannins / Q000378:metabolism*; D007700:Kinetics; D055432:Metabolomics; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D065856:Rubus / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014532:Uridine Diphosphate Glucose / Q000378:metabolism
chemical_list: D047348:Hydrolyzable Tannins; D010940:Plant Proteins; D004610:Ellagic Acid; C060474:glucogallin; D016695:Glycosyltransferases; D014532:Uridine Diphosphate Glucose
keywords: Ellagic acid; Fragaria; Rubus.; ellagitannin; glucose ester; glycosyltransferase; β-glucogallin