Control of CYP metabolic function (How Oxidative Systems Metabolize Substrates) (Human Drug Metabolism)

Although CYPs appear to be part of an impressive and flexible system for the oxidation of drugs, it is not enough just to process endogenous and xenobiotic molecules at a set rate. Endogenous and exogenous CYP substrates can vary enormously in their concentrations within the body, even on a day-to-day basis. As we have seen, steroid hormone levels must be matched to accomplish specific tasks in narrow time frames, so production and destruction must be under exceedingly fine control. This is apparent during the menstrual cycle and pregnancy. Our exposure to various exogenous chemicals, including drugs, is also variable in terms of concentration and physicochemical properties. As an advertising campaign once said, ‘power is nothing without control’. It is essential for the CYP system to be finely controllable to respond to the often extreme changes in the small-molecular weight chemical presence in cells. This process of CYP induction mentioned briefly earlier will be discussed in detail in terms of mechanism and clinical consequences in the next topic.

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