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Accession number;04A0258622
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| Title;Oxygenation Mechanism of Phenols by Tyrosinase. |
| Author;
YAMAZAKI SHIN'ICHI
(Hanshidai In)
ITO SHINOBU
(Hanshidai In)
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Journal Title;Abstracts. Symposium on Biofunctional Chemistry
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Journal Code:L0836A
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ISSN:
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VOL.18th;NO.;PAGE.80-81(2003)
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| Figure&Table&Reference;FIG.1, REF.2 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;Tyrosinase is a copper monooxygenase that catalyzes oxygenation of phenols to catechols (phenolase activity) and oxidation of catechols to the corresponding o-quinones (catecholase activity). Among the catalytic processes of tyrosinase, the phenol oxygenation step has attracted much interest not only in bioinorganic chemistry but also in the fields of coordination chemistry and synthetic organic chemistry. However, mechanistic details of the oxygen atom transfer process from oxy-tyrosinase to the phenol substrates remains ambiguous in spite of the long-standing efforts in the mechanistic studies of tyrosinase. This is mainly due to the ambivalent actions of catechols. Namely, catechols are the indispensable reductant for the regeneration of deoxy-tyrosinase from met-tyrosinase, but they can also be the substrates toward oxy-tyrosinase. In this study, we present a very simple enzymatic reaction system using borate as a trapping agent of catechols and hydroxylamine as an external reductant. With this simplified enzymatic reaction system, we succeeded to examine the phenolase activity without the interference of catecholase reactions to demonstrate that the enzymatic oxygenation reaction of phenols proceeds via the same mechanism as the model reaction, that is, electrophilic aromatic substitution mechanism. (author abst.) |
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