Abstract
Currently, the major recognized biochemical functions of members of the large superfamily of P450 hemoproteins (referred to commonly as the cytochromes P450) include catalyses of the monooxygenations of a wide variety of endogenous and exogenous lipophilic chemicals. Substrates that have attracted the greatest attention thus far are steroids, fatty acids, eicosanoids, retinoids, other endogenous lipids, therapeutic agents, pesticides/herbicides, chemical carcinogens, industrial chemicals and other environmental contaminants and toxic xenobiotic organics of low molecular weight. Commonly, monooxygenation of such substrates results in the generation of metabolites capable of producing biological effects that are profoundly different (qualitatively as well as quantitatively) from those elicitable by the parent chemical per se. P450XIX-dependent conversion of testosterone to estradiol-17β provides a dramatic example. Thus, these hemoproteins serve as extremely important but, as yet, largely unpredictable Full-size image (