Tyrosinase Reactivity in a Model Complex: An Alternative Hydroxylation Mechanism.
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| Title: | Tyrosinase Reactivity in a Model Complex: An Alternative Hydroxylation Mechanism. |
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| Authors: | Mirica, Liviu M., Vance, Michael, Rudd, Deanne Jackson, Hedman, Britt, Hodgson, Keith O., Solomon, Edward I., Stack, T. Daniel P. |
| Source: | Science (pre-March 2025). 6/24/2005, Vol. 308 Issue 5730, p1890-1892. 3p. |
| Subjects: | Metalloenzymes, Aromatic compounds, Polyphenols, Absorption, Physical & theoretical chemistry, Enzymes |
| Abstract: | The binuclear copper enzyme tyrosinase activates O[sub 2] to forma µ-η[sup 2]:η[sup 2]-peroxodicopper(II) complex, whichoxidizes phenols to catechols. Here, a synthetic µ-η[sup2]:η[sup 2]-peroxodicopper(II) complex, with an absorption spectrumsimilar to that of the enzymatic active oxidant, is reported to rapidlyhydroxylate phenolates at -80°C. Upon phenolate addition at extremetemperature in solution (-120°C), a reactive intermediate consistentwith a bis-µ-oxodicopper(III)-phenolate complex, with the O-O bondfully cleaved, is observed experimentally. The subsequent hydroxylationstep has the hallmarks of an electrophilic aromatic substitutionmechanism, similar to tyrosinase. Overall, the evidence for sequentialO-O bond cleavage and C-O bond formation in this synthetic complexsuggests an alternative intimate mechanism to the concerted or latestage O-O bond scission generally accepted for the phenol hydroxylationreaction performed by tyrosinase. [ABSTRACT FROM AUTHOR] |
| Copyright of Science (pre-March 2025) is the property of American Association for the Advancement of Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Psychology and Behavioral Sciences Collection |
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| Abstract: | The binuclear copper enzyme tyrosinase activates O[sub 2] to forma µ-η[sup 2]:η[sup 2]-peroxodicopper(II) complex, whichoxidizes phenols to catechols. Here, a synthetic µ-η[sup2]:η[sup 2]-peroxodicopper(II) complex, with an absorption spectrumsimilar to that of the enzymatic active oxidant, is reported to rapidlyhydroxylate phenolates at -80°C. Upon phenolate addition at extremetemperature in solution (-120°C), a reactive intermediate consistentwith a bis-µ-oxodicopper(III)-phenolate complex, with the O-O bondfully cleaved, is observed experimentally. The subsequent hydroxylationstep has the hallmarks of an electrophilic aromatic substitutionmechanism, similar to tyrosinase. Overall, the evidence for sequentialO-O bond cleavage and C-O bond formation in this synthetic complexsuggests an alternative intimate mechanism to the concerted or latestage O-O bond scission generally accepted for the phenol hydroxylationreaction performed by tyrosinase. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00368075 |
| DOI: | 10.1126/science.1112081 |
