label: aureusidin synthase activity
label_lc: aureusidin synthase activity
description: "Catalysis of the reactions: 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, and 2',3,4,4',6'-pentahydroxychalcone 4'-O-beta-D-glucoside + H+ + O2 = bracteatin 6-O-beta-glucoside + H2O. This activity consists of two separate chemical transformations: 3-hydroxylation and oxidative cyclization (2',-dehydrogenation)."