An Aromatic Dyad Motif in Dye Decolourising Peroxidases Has Implications for Free Radical Formation and Catalysis
Autor: | Jonathan A. R. Worrall, Michael A. Hough, Tadeo Moreno Chicano, Amanda K. Chaplin, Dimitri A. Svistunenko, Bethany V. Hampshire, Michael T. Wilson |
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Rok vydání: | 2018 |
Předmět: |
Models
Molecular Free Radicals Stereochemistry Protein Conformation Radical Amino Acid Motifs Context (language use) 010402 general chemistry 01 natural sciences Catalysis law.invention chemistry.chemical_compound law Computer Simulation Electron paramagnetic resonance Coloring Agents Free Radical Formation biology 010405 organic chemistry Organic Chemistry Substrate (chemistry) General Chemistry Porphyrin 0104 chemical sciences Kinetics chemistry Peroxidases Biocatalysis biology.protein Streptomyces lividans Oxidation-Reduction Algorithms Peroxidase |
Zdroj: | Chemistry (Weinheim an der Bergstrasse, Germany). 25(24) |
ISSN: | 1521-3765 |
Popis: | Dye decolouring peroxidases (DyPs) are the most recent class of heme peroxidase to be discovered. On reacting with H2 O2 , DyPs form a high-valent iron(IV)-oxo species and a porphyrin radical (Compound I) followed by stepwise oxidation of an organic substrate. In the absence of substrate, the ferryl species decays to form transient protein-bound radicals on redox active amino acids. Identification of radical sites in DyPs has implications for their oxidative mechanism with substrate. Using a DyP from Streptomyces lividans, referred to as DtpA, which displays low reactivity towards synthetic dyes, activation with H2 O2 was explored. A Compound I EPR spectrum was detected, which in the absence of substrate decays to a protein-bound radical EPR signal. Using a newly developed version of the Tyrosyl Radical Spectra Simulation Algorithm, the radical EPR signal was shown to arise from a pristine tyrosyl radical and not a mixed Trp/Tyr radical that has been widely reported in DyP members exhibiting high activity with synthetic dyes. The radical site was identified as Tyr374, with kinetic studies inferring that although Tyr374 is not on the electron-transfer pathway from the dye RB19, its replacement with a Phe does severely compromise activity with other organic substrates. These findings hint at the possibility that alternative electron-transfer pathways for substrate oxidation are operative within the DyP family. In this context, a role for a highly conserved aromatic dyad motif is discussed. |
Databáze: | OpenAIRE |
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