Specificity analysis and mechanism of aurone synthesis catalyzed by aureusidin synthase, a polyphenol oxidase homolog responsible for flower coloration.
Aureusidin synthase, which plays a key role in the yellow coloration of snapdragon flowers, is a homolog of plant polyphenol oxidase (PPO). The enzyme specifically acted on chalcones with a 4-monohydroxy or 3,4-dihydroxy B-ring to produce aurones, for whose production the oxidative cyclization of chalcones must be preceded by 3-oxygenation. However, it exhibited virtually no PPO activity toward non-chalcone phenolics. The enzyme was competitively inhibited by phenylthiourea, a specific PPO inhibitor. These results led us to propose a mechanism of aurone synthesis by aureusidin synthase on the basis of known PPO-catalyzed reactions and conclude that the enzyme is a chalcone-specific PPO specialized for aurone biosynthesis.
Nakayama
T
T
Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
Sato
T
T
Fukui
Y
Y
Yonekura-Sakakibara
K
K
Hayashi
H
H
Tanaka
Y
Y
Kusumi
T
T
Nishino
T
T
D001572:Benzofurans / Q000737:chemistry / Q000378:metabolism*; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D002599:Chalcone / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D047188:Chalcones; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019684:Magnoliopsida / Q000201:enzymology* / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D010858:Pigmentation; D018514:Plant Structures / Q000201:enzymology / Q000378:metabolism*; D013379:Substrate Specificity
D001572:Benzofurans; D047188:Chalcones; D004791:Enzyme Inhibitors; C416232:aureusidin; D002599:Chalcone; C027329:naringenin chalcone; D006899:Mixed Function Oxygenases; C416231:aureusidin synthase; D004156:Catechol Oxidase