CYP

In the following sections, the abbreviation used for nomenclature and searching is given at the start of each section. Some of these are not unique (e.g., CYP, COX) and are shared with other genes/enzymes, and alternative searches are recommended. 

The general stoichiometry of P450 reactions is mixed-function oxidation (R = substrate). 

In some cases the stoichiometry is less obvious because of rearrangements of the product (carbinolamines in N-dealkylation) or variations on the general mechanism (desaturations). 

TABLE 2.1 Classification of human P450s based on major substrate class (Gnengerich, 2005 Gnengerich et al., 2006)  

Sterols Xenobiotics Fatty acids Ficosanoids Vitamins Unknown 

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MDR-ABC Transporters. Figure 3 Detoxification cellular mechanisms. X, toxic compound X-OH, oxidized toxic compound GS-X, conjugated toxic compound OATP, organic anion transporting proteins CYPs, cytochromes GSH, glutathion UDPGIcUA, Uridine 5-diphosphoglucuronic acid PAPs, 3-phosphoadenylylsulfate. 

Nuclear Receptor Regulation of Hepatic Cytochrome P450 Enzymes. Figure 1 General mechanism for transcriptional activation of CYP genes by xenochemicals that activate their cognate xeno-receptor proteins. In the case of Ah receptor, the receptor s heterodimerization partner is Arnt, whereas in the case of the nuclear receptors CAR, PXR, and PPARa, the heterodimerization partner is RXR. The coactivator and basal transcription factor complexes shown are each comprised of a large number of protein components. 

Cytochrome P450 (CYP) Cytochrome P450 isozymes Cytochrome P450 mono-oxygenases Mixed function oxidases... 

Cytochrome P450 (CYP) mono-oxygenases, also called mixed function oxidases, are versatile hemoprotein enzymes that catalyze the cleavage of molecular oxygen to incoiporate one oxygen atom into a substrate molecule and one atom into water [1]. The general stoichiometry of the reaction is as follows (S-H, substrate) ... 

The numerous biotransformations catalyzed by cytochrome P450 enzymes include aromatic and aliphatic hydroxylations, epoxidations of olefinic and aromatic structures, oxidations and oxidative dealkylations of heteroatoms and as well as some reductive reactions. Cytochromes P450 of higher animals may be classified into two broad categories depending on whether their substrates are primarily endogenous or xenobiotic substances. Thus, CYP enzymes of families 1-3 catalyze... 

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