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Aureusidin synthase
Aureusidin synthase (, ''AmAS1'') is an enzyme with system name ''2',4,4',6'-tetrahydroxychalcone 4'-O-beta-D-glucoside:oxygen oxidoreductase''.
Aureusidin synthase has two main enzymatic tasks: hydroxylation at the 3-position on the B-ring of chalcones, and the oxidative cyclization of chalcones to form aurones.〔 The chalcones modified are typically glucosylated 2',4,4',6'-tetrahydroxychalcone (THC) and 2',3,4,4',6'-pentahydroxychalcone (PHC).〔 These aurones, particularly auresidin, form pigments for coloration in flowers.〔 These pigments may have been developed to attract and guide bees for pollination, but they also provide protection from viruses, pests and fungus.
== Enzyme structure ==
Aureusidin synthase is a 39 kDa monomeric glycoprotein containing binuclear copper.〔 The addition of phenylthiourea, which competitively binds to binuclear copper, inhibits the enzyme's productivity overall.〔 Because of this, it is likely that the active site contains the binuclear copper.
Aureusidin synthase is homologous to plant polyphenol oxidase (PPO),〔 but contains certain significant modifications. While PPO has a highly conserved N-terminal amino acid sequence in order to facilitate transport to the plastid lumen, aureusidin synthase lacks this sequence〔 and thus is not localized to the plasmid. Much like PPOs, aureusidin synthase is likely first synthesized as a larger ~60 kDa protein and then undergoes proteolytic cleavage to remove transport groups.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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