Drug activation by cytochromes : good or bad?

Cytochromes P450 are oxygenases, i.e. enzymes capable of inserting an oxygen atom from molecular oxygen into a substrate, even one of low reactivity. These enzymes, present in all living species, animal or vegetable, are involved in the activation of endogenous or exogenous substrates. The detailed mechanism of their catalytic cycle enables us to understand their role in detoxification reactions or in the formation of intermediates that may present a certain toxicity. All these different activities have been discussed at the molecular level. Precise knowledge of the activation of drugs by cytochromes P450 enables us to understand their metabolism, and also to prevent intoxication in the case of induction of certain cytochromes by certain therapeutic agents.