Aureusidin synthase

Nakayama, T. Yonekura-Sakakibara, K. Sato, T. Kikuchi, S. Fukui, Y. Fukuchi-Mizutani, M. Nakao, M. Tanaka, Y. Kusumi, T. Nishino, T. (2000) Aureusidin synthase polyphaiol oxidase homolog responsible for flower coloration. Science, 290, 1163-6. 

Although it has long been thought, based on genetic mutant and biochemical evidence, that aurones are derived from chalcones, the biosynthetic mechanism has only recently been clarified, and some aspects of the enzymatic process still await in vivo proof An mRNA from A. majns, specifically expressed in the petal epidermal cells, has been shown to encode a recombinant protein with aureusidin synthase (AUS) activity.AUS is a variant polyphenol oxidase (PPO) that can catalyze conversion of either 2, 4, 6, 4-etrahydroxychalcone (naringenin chalcone) or 2, 4, 6, 3,4-pentahydroxychalcone to... 

Nakayama, T. et al., Aureusidin synthase a polyphenol oxidase homolog responsible for flower coloration. Science, 290, 1163, 2000. 

FIGURE 16.S Reactions catalyzed by the plant polyphenol oxidase, aureusidin synthase (AS), in the transformation of chalcones to aurones. (A) The biosynthesis of aureusidin from either tetra- or pentahydroxychalcone precursors through an ortho-diqmnone intermediate. (B) The aureusidin synthase-catalyzed formation of bracteatin from a pentahydroxychalcone precursor. 

Figure 3-7. Flavonoid biosynthesis (this page and next page). The enzymes involved in this pathway are (a) chalcone synthase (E.C. 2.3.1.73), (b) aureusidin synthase (E.C. 1.21.3.6), (c) chalcone isomerase (E.C. 5.5.1.6), (d) flavanone 3-hydroxylase (E.C. 1.14.11.9), (e) flavone synthase (E.C. 1.14.11.22), (f) flavonoid 3 -hydroxylase (E.C. 1.14.13.21),...

Nakayama T, Sato T, Fukui Y, Yonekura-Sakakibara K, Hayashi H, Tanaka Y, Kusumi T, Nishino T. 2001. Specificity analysis and mechanism of aurone synthesis catalyzed by aureusidin synthase, a polyphenol oxidase homolog responsible for flower coloration. FEBS Lett 499 107-111. 

Aureusidin synthase (AmASl), 1889 Aurones, 1621, 1887, 1889 Australian ewes, 2417 Autolyzate, 978-979 Autooxidation, 2370 Autopsy, 2409 Autumnaline, 461-476 Auxins, 192, 1830, 2774, 3198, 3591, 4044 Avenalumin I, 1569 Avena sativa, 1569 Avicermiaceae, 1552 Axinellamines, 268 Axinohydantoin, 268 Axonal membrane, 4065 Axone regeneration, 3219 Ayahuasca, 125, 1452 Ayurvedic, 1278, 3960 formulations, 3327, 3328 medications, 1399 medicinal system, 3476... 

Another example arguing for vacuolar locahzation of distinct biosynthetic steps is the finding that the oxidative formation of the yellow aurones in snapdragon flowers from chalcones via aureusidin synthase, a polyphenol oxidase (PPO), occurs in the vacuole. This may represent a means to overcome the instability of the precursor chalcones in the cytosol and to concentrate aurones in the flower (Ono et al., 2006). 

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