title: Structure and mechanism of anthocyanidin synthase from Arabidopsis thaliana.
abstract: Flavonoids are common colorants in plants and have long-established biomedicinal properties. Anthocyanidin synthase (ANS), a 2-oxoglutarate iron-dependent oxygenase, catalyzes the penultimate step in the biosynthesis of the anthocyanin class of flavonoids. The crystal structure of ANS reveals a multicomponent active site containing metal, cosubstrate, and two molecules of a substrate analog (dihydroquercetin). An additional structure obtained after 30 min exposure to dioxygen is consistent with the oxidation of the dihydroquercetin to quercetin and the concomitant decarboxylation of 2-oxoglutarate to succinate. Together with in vitro studies, the crystal structures suggest a mechanism for ANS-catalyzed anthocyanidin formation from the natural leucoanthocyanidin substrates involving stereoselective C-3 hydroxylation. The structure of ANS provides a template for the ubiquitous family of plant nonhaem oxygenases for future engineering and inhibition studies.
authors.affiliation: The Dyson Perrins Laboratory, Oxford Centre for Molecular Sciences, South Parks Road, Oxford OX1 3QY, United Kingdom. rupert.wilmouth@new.ox.ac.uk
authors.forename: Rupert C
authors.initials: RC
authors.lastname: Wilmouth
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Turnbull
authors.forename: Richard W D
authors.initials: RW
authors.lastname: Welford
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Clifton
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Prescott
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schofield
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010105:Oxygenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D010105:Oxygenases; C118159:anthocyanidin synthase