Reaction: (1) 2',4,4',6'-tetrahydroxychalcone + O2 = aureusidin + H2O
(2) 2',3,4,4',6'-pentahydroxychalcone + ½ O2 = aureusidin + H2O
For diagram click here.
Glossary: chalcone = 1,3-diphenylprop-2-en-1-one
Other name(s):
Systematic name: 2',4,4',6'-tetrahydroxychalcone:oxygen oxidoreductase
Comments: A copper-containing glycoprotein that plays a key role in the yellow coloration of flowers such as snapdragon. The enzyme is a homologue of plant polyphenol oxidase [1] and catalyses two separate chemical transformations, i.e. 3-hydroxylation and oxidative cyclization (2',α-dehydrogenation). H2O2 activates reaction (1) but inhibits reaction (2).
Links to other databases: BRENDA, EXPASY, KEGG, CAS registry number: 320784-48-3
References:
1. Nakayama, T., Yonekura-Sakakibara, K., Sato, T., Kikuchi, S., Fukui, Y., Fukuchi-Mizutani, M., Ueda, T., Nakao, M., Tanaka, Y., Kusumi, T. and Nishino, T. Aureusidin synthase: A polyphenol oxidase homolog responsible for flower coloration. Science 290 (2000) 1163-1166. [PMID: 11073455]
2. Nakayama, T., Sato, T., Fukui, Y., Yonekura-Sakakibara, K., Hayashi, H., Tanaka, Y., Kusumi, T. and Nishino, T. Specificity analysis and mechanism of aurone synthesis catalyzed by aureusidin synthase, a polyphenol oxidase homolog responsible for flower coloration. FEBS Lett. 499 (2001) 107-111. [PMID: 11418122]
3. Sato, T., Nakayama, T., Kikuchi, S., Fukui, Y., Yonekura-Sakakibara, K., Ueda, T., Nishino, T., Tanaka, Y. and Kusumi, T. Enzymatic formation of aurones in the extracts of yellow snapdragon flowers. Plant Sci. 160 (2001) 229-236. [PMID: 11164594]