Cytochrome P450: Structure and States

The cytochrome P450 monoxygenases assume a significant role in the elucidation of heme-iron mechanisms of oxygenation and O2 reduction. The P450 monoxygenases mediate a two-electron activation of O2 resulting in a molecule of H2O and the insertion of a single O atom into a hydrocarbon substrate (1). The P450 reaction cycle illustrates a redox controlled pathway of Fe-O reactivity which supplements our understanding of 1) heme-O2 binding in Mb and Hb, with 2) electron transfer in respiratory cytochromes and 3) oxygen activation of the peroxidases. A broad base of interdisciplinary study has contributed to the characterization of this physiologically important process. The P450 cytochromes refer to a general class of mixed function oxidases, who are widely distributed in nature and display diverse biological activity towards hydrocarbon substrates (2,3). In eukaryotes, and mammals in particular, the range of P450 functions is extensive and includes detoxification of xenobiotics, the activation of carcinogenes and the biosynthesis of regulatory steroid hormones. The prokaryotes are best represented by a P450 monoxygenase from P. putida that initiates the degradation of its growth substrate camphor (4).