Tyrosinase Reactivity in a Model Complex: An Alternative Hydroxylation Mechanism
- 24 June 2005
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 308 (5730) , 1890-1892
- https://doi.org/10.1126/science.1112081
Abstract
The binuclear copper enzyme tyrosinase activates O 2 to form a μ-η 2 :η 2 -peroxodicopper(II) complex, which oxidizes phenols to catechols. Here, a synthetic μ-η 2 :η 2 -peroxodicopper(II) complex, with an absorption spectrum similar to that of the enzymatic active oxidant, is reported to rapidly hydroxylate phenolates at –80°C. Upon phenolate addition at extreme temperature in solution (–120°C), a reactive intermediate consistent with a bis-μ-oxodicopper(III)-phenolate complex, with the O–O bond fully cleaved, is observed experimentally. The subsequent hydroxylation step has the hallmarks of an electrophilic aromatic substitution mechanism, similar to tyrosinase. Overall, the evidence for sequential O–O bond cleavage and C–O bond formation in this synthetic complex suggests an alternative intimate mechanism to the concerted or late stage O–O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase.Keywords
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