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Spectroscopic characterization of the iron-oxo intermediate in cytochrome P450

Item Type:Article
Title:Spectroscopic characterization of the iron-oxo intermediate in cytochrome P450
Creators Name:Jung, C. and Schuenemann, V. and Lendzian, F. and Trautwein, A.X. and Contzen, J. and Galander, M. and Boettger, L.H. and Richter, M. and Barra, A.L.
Abstract:From analogy to chloroperoxidase from Caldariomyces fumago, It is believed that the electronic structure of the intermediate iron-oxo species in the catalytic cycle of cytochrome P450 corresponds to an iron(IV) porphyrin-π-cation radical (compound I). However, our recent studies on P450cam revealed that after 8 ms a tyrosine radical and iron(IV) were formed in the reaction of ferric P450 with external oxidants in the shunt pathway. The present study on the heme domain of P450BM3 (P450BMP) shows a similar result. In addition to a tyrosine radical, a contribution from a tryptophan radical was found in the electron paramagnetic resonance (EPR) spectra of P450BMP. Here we present comparative multifrequency EPR (9.6, 94 and 285 GHz) and Mössbauer spectroscopic studies on freeze-quenched intermediates produced using peroxy acetic acid as oxidant for both P450 cytochromes. After 8 ms in both systems, amino acid radicals occurred instead of the proposed iron(IV) porphyrin-π-cation radical, which may be transiently formed on a much faster time scale. These findings are discussed with respect to other heme thiolate proteins. Our studies demonstrate that intramolecular electron transfer from aromatic amino acids is a common feature in these enzymes. The electron transfer quenches the presumably transiently formed porphyrin-π-cation radical, which makes it extremely difficult to trap compound I.
Keywords:Compound 1, Moessbauer Spectroscopy, Multi-Fequency EPR, Radicals, Rapid-mixing, Thiolate heme proteins
Source:Biological Chemistry
Publisher:de Gruyter
Page Range:1043-1053
Date:1 October 2005
Official Publication:https://doi.org/10.1515/BC.2005.120
PubMed:View item in PubMed

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