The unusual hemoprotein called cytochrome P450 is now
recognized as representing a variety of monooxygenases with
entirely different substrate specificities. In comparison with hememercaptide
models it can be concluded that the unusual spectral
properties reside in a heme-mercaptide linkage to the protein. The
sixth ligand in the ferric form could be a hydroxyl group which
is absent in the enzyme-substrate complex. In the reaction cycle
the enzyme-substrate complex is reduced and then reacts with
dioxygen to form an oxy-complex. Further reduction is believed to
yield an »oxenoid« complex of the structure [Fe0]3+, which transfers
the oxygen atom to the substrate
