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|Title:||Tryptophan Radicals as Reaction Intermediates in Versatile Peroxidases: Combined Multifrequency EPR/ENDOR and Density Functional Theory Studies||Authors:||Pogni, Rebecca
|Issue Date:||2007||Project:||None||Journal:||APPLIED MAGNETIC RESONANCE||Abstract:||
Versatile peroxidases are a new class of ligninolytic enzymes secreted by fungi from thegroup of white-rot basidiomycetes. Versatile peroxidase (VP) is a structuml hybrid between ligninand manganese peroxidase. This hybrid combines the catalytic properties of the two above peroxidasesbeing able to catalyze Mn(II)-dependent and Mn(lI)-independent reactions. A long-range electrontransfer mechanism has been inferred for the oxidation of big substrate molecules starting fromah exposed tryptophan to the heme cofactor. A neutral tryptophan radical has been identified in VPfrom Bjerkandera adusta and Pleurotus eryngii, after H202 activation and assignr to a specific tryptophanresidue using multifrequency electron paramagnetic resonance and electron-nuclear doubleresonance spectroscopy. Comparative density functional theory calculations were performed for tryptophanneutral and cation radical species, considering also the effect of the polar environment surroundingthe radical. The functional role of the radicals is discussed in the context of mechanisticmodels for VP.
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