A copper-containing glycoprotein that plays a key role in the yellow coloration of flowers such as Antirrhinum majus (snapdragon). The enzyme is a homologue of plant polyphenol oxidase  and catalyses two separate chemical transformations, i.e. 3-hydroxylation and oxidative cyclization (2',-dehydrogenation). H2O2 activates reaction (1) but inhibits reaction (2). Originally considered to act on the phenol but now thought to mainly act on the 4'-O-beta-D-glucoside in vivo .
expression in Nicotiana tabacum and Lactuca sativa leads to plants that display a functionally active chalcone-flavanone biosynthetic pathway. Leaves of the resulting transgenic plants develop a yellow hue and display higher superoxide dismutase inhibiting and oxygen radical absorbance capacity activities than control leaves
no activity with L-tyrosine, L-DOPA, 4-coumaric acid, caffeic acid, naringenin, eriodictyol, 4,4',6'-trihydroxyaurone, and aureusidin, absolutely specific for chalcones, no activity with 2'-hydroxychalcone, 4-hydroxychalcone, 2',3,4,4',6'-pentahydroxychalcone 3-glucoside, and 2',6'-dihydroxy-4,4'-dimethoxychalcone
two copper atoms, CuA and CuB, are located in the active site and each is coordinated by three histidine residues. CuA is coordinated by His87, His108, and His117 residues, while CuB is coordinated by His241, His245 and His275
modeling of enzyme-phenylthiourea complex. The inhibitor binds with the hydrophobic pocket of the dinuclear copper center. The phenyl ring of Phe262 and the imidazole ring of His245 form hydrophobic interactions with the aromatic ring of the inhibitor. The sulfur atom of the inhibitor replaces the hydroxo-bridge, which is essential for catalysis
homology modeling using grenache polyphenol oxidase and sweet potato catechol oxidase as templates. The structure is folded into 15alpha-helices and 5 beta-sheets, and mostly composed by loops. The core of the enzyme is formed by a four-helix-bundle, and the helical bundle accommodates the dinuclear copper center. The cysteine residues Cys11, Cys25, Cys26, and Cys88 are highly conserved, and form disulfide bridges
natural enzyme mutants sulfurea and violacea showing increased aurone production in petals and reduced aurone production, resp. Enzyme and aureusidin 7-O-glucosyltransferase transcript abundance and spatial pattern is similar in wild-type and mutants. Recessive mutant line CFR1011 with greatly reduced aurone production also shows no change in transcript abundance or any point mutantions in the coding sequences of enzyme or aureusidin 7-O-glucosyltransferase
coexpression of enzyme and chalcone 4-O-glucosyltransferase is sufficient for accumulation of aureusidin 6-O-glucoside in transgenic flowers. Additional down-regulation of anthocyanin biosynthesis by RNAi results in yellow flowers