[The role of cytochrome P450 in the activation of drugs (author's transl)].

Unspecific microsomal monooxygenases have been found in many organisms of different developmental stages. In higher organisms liver is the main organ of drug metabolism but smaller intestine, lung and skin also show this activity. The corresponding membrane-bound enzyme system could be isolated by modern chromatographic techniques and was found to consist of a reductase and a series of cytochrome P450 enzymes. Each of these cytochromes has a different, but with other forms overlapping substrate specificity. The steady-state concentrations of the various forms is regulated by induction with drugs and foreign compounds. The unspecificity of the systems is also reflected in the varying pattern of metabolites. In general stable and more polar metabolites are formed by the monooxygenation reaction, but reactive and unstable products may also appear, e.g. N-hydroxy compounds, 1,2-diphenols, epoxides and a new class of compounds which have been characterized as carbenes.