Involved in the biosynthesis of aurones, plant flavonoids that provide yellow coloration to flowers. Can use tetrahydroxychalcone (THC), pentahydroxychalcone (PHC), THC 4'-glucoside and PHC 4'-glucoside as substrates, but not 2'-hydroxychalcone, 4-hydroxychalcone, PHC 3-glucoside, 2',6'-dihydroxy-4,4'-dimethoxychalcone, naringenin, eriodictyol and 4,4',6-trihydroxyaurone. Can also produce bracteatin from PHC. 2',4,4',6'-tetrahydroxychalcone 4'-O-beta-D-glucoside + H(+) + O2 = aureusidin 6-O-beta-glucoside + H2O 2 2',3,4,4',6'-pentahydroxychalcone 4'-O-beta-D-glucoside + 2 H(+) + O2 = 2 aureusidin 6-O-beta-glucoside + 2 H2O 2',3,4,4',6'-pentahydroxychalcone 4'-O-beta-D-glucoside + H(+) + O2 = bracteatin 6-O-beta-glucoside + H2O Binds 2 copper ions per subunit. H(2)O(2) activates the 3-hydroxylation and oxidative cyclization of tetrahydroxychalcone but inhibits reaction with pentahydroxychalcone. Inhibited by phenylthiourea. Optimum pH is 5.4 for the reaction with tetrahydroxychalcone and 5.0 - 7.0 for the reaction with pentahydroxychalcone. Monomer. Expressed in petals. Not detected in stems and leaves. The N-terminal sequence (1-53) is sufficient for vacuolar targeting. Glycosylated. Contains probably N- and C-terminal propeptides. Belongs to the tyrosinase family.