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|Title:||A Tryptophan Neutral Radical in the Oxidized State of Versatile Peroxidases from Pleurotus Eryngii: A combined Multifrequency EPR and DFT study||Authors:||Pogni, Rebecca
Baratto, Maria Camilla
F. J., RUIZ DUENAS
A. T., Martinez
|Issue Date:||2006||Project:||None||Journal:||THE JOURNAL OF BIOLOGICAL CHEMISTRY||Abstract:||
Versatile peroxidases are heme enzymes that combine catalytic properties of lignin peroxidases and manganese peroxidases, being able to oxidizeMn2 as well as phenolic and non-phenolic aromatic compounds in the absence of mediators. The catalytic process (initiated by hydrogen peroxide) is the same as in classical peroxidases, with the involvement of 2 oxidizing equivalents and the formation of the so-called Compound I. This latter state contains an oxoferryl center and an organic cation radical that can be located on either the porphyrin ring or a protein residue. In this study, a radical intermediate in the reaction of versatile peroxidase from the ligninolytic fungus Pleurotus eryngii with H2O2 has been characterized by multifrequency (9.4 and 94 GHz) EPR and assigned to a tryptophan residue. Comparison of experimental data and density functional theory theoretical results strongly suggests the assignment to a tryptophan neutral radical, excluding the assignment to a tryptophan cation radical or a histidine radical. Based on the experimentally determined side chain orientation and comparison with a high resolution crystal structure, the tryptophan neutral radical can be assigned to Trp164 as the site involved in long-range electron transfer for aromatic substrate oxidation.
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