Cytochrome P450 refers to a superfamily of haeme proteins present in all mammalian cell types, except mature red blood cells and skeletal muscle cells. It is also known to be widely distributed in plants, micro-organisms and animals. They catalyse the oxidation of a wide variety of structurally diverse compounds. Substrates for these enzyme systems include:

• endogenously synthesised compounds such as steroids, fatty acids (including prostaglandins and leukotrienes) and
• compounds such as drugs, food additives (i.e. flavors), industrial byproducts that enter the body through food sources, injection, inhalation from the air, or absorption through the skin.

• inactivation or activation of therapeutic agents,
• conversion of chemicals to highly reactive molecules which may produce cell damage, death or mutations,
• participate in steroid hormone biosynthesis and
• metabolism of fatty acids and their derivatives.