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Concerted electron/proton transfer mechanism in the oxidation of phenols by laccase (Articolo in rivista)

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Concerted electron/proton transfer mechanism in the oxidation of phenols by laccase (Articolo in rivista) (literal)

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C. Galli, C. Madzak, R. Vadal, C. Jolivalt, P. Gentili (2013)
Concerted electron/proton transfer mechanism in the oxidation of phenols by laccase
in ChemBioChem (Print); WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (Germania)
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Dipartimento di Chimica Universita'La Sapienza\", and IMC-CNR Sezione Meccanismi di Reazione P.le A. Moro 5, 00185 Roma (Italy) INRA, UMR1319 Micalis Domaine de Vilvert, 78352 Jouy-en-Josas (France) Chimie ParisTech Laboratoire Charles Friedel (LCF), and CNRS UMR 7223 11 rue P. et M. Curie, 75005 Paris (France) (literal)

Titolo

Concerted electron/proton transfer mechanism in the oxidation of phenols by laccase (literal)

Abstract

This study aimed to assess structural requirements in the enzyme/substrate interactions that are responsible for tuning the enzymatic reactivity. To better assess the role of the aspartic residue in the substrate-binding pocket of basidiomycetetype laccases, we compared the catalytic efficiency of wildtype enzymes to that of a mutant in which carboxylic acid residue Asp206 was changed to alanine. Oxidation efficiency towards phenolic substrates by laccases of Trametes villosa, Trametes versicolor and a T. versicolor D206A mutant was studied at two pH values. By the Hammett approach and Marcus analysis, we obtained unambiguous evidence that the oxidation takes place by a concerted electron/proton transfer (EPT) mechanism, and that at pH 5 (optimum pH for enzyme activity) the phenolic proton is transferred to Asp206 during the concerted electron/proton transfer process. (literal)

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