Cytochrome P-450 is part of a number of oxygen transfer enzymes such as monooxygenases and peroxidases. It gets its name from the wavelength of light absorbed by its CO complex.
The haem bound iron atom is axially bound by the sulfur atom of a cysteine residue. This allows the iron center to transfer O2 to less attractive substrates such as fatty acids, amino acids and hormones.
It is often found in the liver, where it takes part in detoxification.