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 .
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
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