Cytochromes P-450 and model systems: great diversity of catalyzed reactions

Abs t r a : The most fiequently encountered function of cytochromes P450, the monooxygenation of substrates, is now well understood and depends on the involvement of a high-valent iron-0x0 intermediate. The corresponding reactions have been reproduced by using metalloporphyrin model systems, the most efficient catalysts being Fe(III) or Mn(III) tetraarylporphyrins bearing electron-withdrawing substituents at the P-pyrrole positions. More recently, cytochromes P450 were found able to catalyze very different reactions like isomerisations, reductions and dehydrations. Moreover, nitric oxide synthases are P450-like hemeproteins w5ich contain a heme binding sequence very similar to that of cytochromes P450. These NO synthases could be the most sophisticated members of the P450 superfamily. A