Cytochrome P450 (P450) enzymes catalyze a variety of reactions and convert chemicals
to potentially reactive products as well as make compounds less toxic. Most of the
P450 reactions are oxidations. The majority of these can be rationalized in the context
of an FeO(3+) intermediate and odd electron abstraction/rebound mechanisms; however,
other iron-oxygen complexes are possible and alternate chemistries can be considered.
Another issue regarding P450-catalyzed reactions is the delineation of rate-limiting
steps in the catalytic cycle and the contribution to reaction selectivity. In addition
to the rather classical oxidations, P450s also catalyze less generally discussed reactions
including reduction, desaturation, ester cleavage, ring expansion, ring formation,
aldehyde scission, dehydration, ipso attack, one-electron oxidation, coupling reactions,
rearrangement of fatty acid and prostaglandin hydroperoxides, and phospholipase activity.
Most of these reactions are rationalized in the context of high-valent iron-oxygen
intermediates and Fe(2+) reductions, but others are not and may involve acid-base
catalysis. Some of these transformations are involved in the bioactivation and detoxication
of xenobiotic chemicals.