The functional roles of cytochrome P-450 mediated systems: present knowledge and future areas of investigations.

Research in recent years has considerably enhanced our understanding of the membrane-bound cytochrome P-450-catalyzed biotransformations in organisms. A remarkable similarity has become apparent between diversified animal groups with respect to the components and functional roles of the cytochrome P-450 systems. For example, the steroidal hormone metabolism role for this cytochrome in mammals was recently extended to insect species. In addition, this cytochrome functions importantly in mammalian species for the metabolism of a variety of other endogenous substrates such as bile acids, anthranilic acid, fatty acids, bilirubin and heme, indoles, amines, and purines. Regarding the exogenous role, the system has been known to convert toxic lipophilic substances such as drugs and insecticides to more hydrophilic metabolites which can be easily eliminated by the water-based excretory system in organisms. This detoxication ability apparently arose in organisms, particularly the herbivores, in response to the need to detoxify plant-defensive toxins such as tannins, phenols, quinones, alkaloids, steroids, lecithins, and lignins. The interface between plants and insects is enormous, and therefore it appears probable that cytochrome P-450 will one day be shown to be important in the conversion/utilization of other plant secondary substances, e.g., synthesis of cholesterol from phytosterols, and sex pheromones from olefins, terpenes, and alkaloids.