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Direct EPR Observation of a Tyrosyl Radical in a Functional Oxidase Model in Myoglobin during both H2O2 and O2 Reactions

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journal contribution
posted on 29.01.2014 by Yang Yu, Arnab Mukherjee, Mark J. Nilges, Parisa Hosseinzadeh, Kyle D. Miner, Yi Lu
Tyrosine is a conserved redox-active amino acid that plays important roles in heme–copper oxidases (HCO). Despite the widely proposed mechanism that involves a tyrosyl radical, its direct observation under O2 reduction conditions remains elusive. Using a functional oxidase model in myoglobin called F33Y-CuBMb that contains an engineered tyrosine, we report herein direct observation of a tyrosyl radical during both reactions of H2O2 with oxidized protein and O2 with reduced protein by electron paramagnetic resonance spectroscopy, providing a firm support for the tyrosyl radical in the HCO enzymatic mechanism.