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Freeze-quenched iron-oxo intermediates in cytochromes P450

Item Type:Review
Title:Freeze-quenched iron-oxo intermediates in cytochromes P450
Creators Name:Jung, C. and Schuenemann, V. and Lendzian, F.
Abstract:Since the discovery of cytochromes P450 and their assignment to heme proteins a reactive iron-oxo intermediate as the hydroxylating species has been discussed. It is believed that the electronic structure of this intermediate corresponds to an iron(IV)-porphyrin-π-cation radical system (Compound I). To trap this intermediate the reaction of P450 with oxidants (shunt pathway) has been used. The common approaches are stopped-flow experiments with UV-visible spectroscopic detection or rapid-mixing/freeze-quench studies with EPR and Mössbauer spectroscopic characterization of the trapped intermediate. Surprisingly, the two approaches seem to give conflicting results. While the stopped-flow data indicate the formation of a porphyrin-π-cation radical, no such species is seen by EPR spectroscopy, although the Mössbauer data indicate iron(IV) for P450cam (CYP101) and P450BMP (CYP102). Instead, radicals on tyrosine and tryptophan residues are observed. These findings are reviewed and discussed with respect to intramolecular electron transfer from aromatic amino acids to a presumably transiently formed porphyrin-π-cation radical.
Keywords:Compound I, Moessbauer spectroscopy, Multifrequency EPR, Radicals, Rapid Mixing, Thiolate Heme Proteins, Animals
Source:Biochemical and Biophysical Research Communications
ISSN:0006-291X
Publisher:Academic Press (U.S.A.)
Volume:338
Number:1
Page Range:355-364
Date:29 August 2005
Official Publication:https://doi.org/10.1016/j.bbrc.2005.08.166
PubMed:View item in PubMed

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