Cytochromes P450 (CYPs) are a family of enzymes containing heme as a cofactor that function as monooxygenases.[1] In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown. In plants, these proteins are important for the biosynthesis of defensive compounds, fatty acids, and hormones.[2]
CYP enzymes have been identified in all kingdoms of life: animals, plants, fungi, protists, bacteria, archaea, and even in viruses.[3] However, they are not omnipresent; for example, they have not been found in Escherichia coli.[4][5] More than 50,000 distinct CYP proteins are known.[6]
CYPs are, in general, the terminal oxidase enzymes in electron transfer chains, broadly categorized as P450-containing systems. The term "P450" is derived from the spectrophotometric peak at the wavelength of the absorption maximum of the enzyme (450 nm) when it is in the reduced state and complexed with carbon monoxide. Most CYPs require a protein partner to deliver one or more electrons to reduce the iron (and eventually molecular oxygen).
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