Identification of a Radical Intermediate in the Enzymatic Reduction of Oxygen by a Small Laccase

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• 作者：Armand W.J.W. Tepper ; Sergey Milikisyants ; Silvia Sottini ; Erik Vijgenboom ; Edgar J.J. Groenen ; Gerard W. Canters
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：August 26, 2009
• 年：2009
• 卷：131
• 期：33
• 页码：11680-11682
• 全文大小：207K
• 年卷期：v.131,no.33(August 26, 2009)
• ISSN：1520-5126

文摘

The enzyme mechanism of the Cu-containing small laccase (SLAC) from Streptomyces coelicolor has been investigated by optical and electron paramagnetic resonance spectroscopy. A new intermediate was identified after the reaction of molecular oxygen with the reduced trinuclear site of the type-1-depleted (T1D) form of the enzyme. It has the fingerprint of a biradical with a triplet ground state. One of the spins resides on a Cu in the trinuclear site, tentatively identified as the type-2 site, while the other spin derives from a protein-based radical. The latter is tentatively identified as a tyrosyl radical on the basis of the similarity of the optical characteristics with those observed for a Cu tyrosyl radical pair. The spin−spin distance was found to be 5.0 ± 0.2 Å.