Cytochrome P450/Models

Jennifer Cheek

Jennifer Cheek

University of South Carolina, Columbia, South Carolina

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Eric D. Coulter

Eric D. Coulter

University of South Carolina, Columbia, South Carolina

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John H. Dawson

John H. Dawson

University of South Carolina, Columbia, South Carolina

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First published: 15 July 2002

Abstract

Cytochrome P450 is a monooxygenase that contains an iron heme active site. This enzyme catalyzes the activation of molecular oxygen with the resulting insertion of one oxygen atom into organic substrates. In order to understand how this catalytic system functions, it is essential to know the structure of the active site and the changes that this catalytic center undergoes during its reaction cycle. Over the past 40 years, this has been a subject of intense research and has resulted in an abundance of both structural and mechanistic knowledge. Several researchers have succeeded in mimicking many of the properties of cytochrome P450 using synthetic porphyrins and genetically engineered mutants of other well-characterized heme proteins. Furthermore, the activity of P450 can be manipulated extensively through the use of genetic engineering and carefully constructed substrates. However, P450 researchers continue to ask the fundamental question: how does the enzyme activate dioxygen? The involvement of an oxoferryl porphyrin π-cation radical as the “active oxygen” intermediate in the P450 reaction cycle has long been suspected, but it has not yet been observed during dioxygen- and substrate-dependent turnover of the enzyme. Nonetheless, by focusing on the similarities between P450 enzymes and the peroxidases, a significantly higher degree of understanding of P450 mechanism of action has been developed.

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