Cytochrome P450 - Wikipedia
"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 CO.
CYP enzymes have been identified in all domains of life - animals, plants, fungi, protists, bacteria, archaea, and even in viruses. However, the enzymes have not been found in E. coli. More than 21,000 distinct CYP proteins are known.Most CYPs require a protein partner to deliver one or more electrons to reduce the iron (and eventually molecular oxygen). "