Reactive metabolites categories

As a result of their high reactivity, reactive metabolites are often considered to be short-lived. This is not always true, however, because reactive intermediates can be transported from one tissue to another, where they may exert their deleterious effects. Thus reactive intermediates can be divided into several categories depending on their half-life under physiological conditions and how far they may be transported from the site of activation. 

These are metabolites that bind primarily to the parent enzyme. This category includes substrates that form enzyme-bound intermediates that react with the active site of the enzyme. Such chemicals are known as suicide substrates. A number of compounds are known to react in this manner with CYP, and such compounds are often used experimentally as CYP inhibitors (see the discussion of piperonyl butoxide, Section 7.2.2). Other compounds, although not true suicide substrates, produce reactive metabolites that bind primarily to the activating enzyme or adjacent proteins altering the function of the protein. 

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