Cytochrome P450 are important detoxification enzymes that often perform the first step in the degradation of foreign compounds (see right). In the words of toxicologists they are the archetypal 'phase one' enzymes, and usually (but not always) act by adding an oxygen to a chemical substrate. Their name comes from their characteristic absorption of light with a wave length of 450nm that can be attributed to a heme moiety in their catalytic centre.
We have found that the P450 complement of Drosophila species varies from 74-94 per genome and estimate that the ancestral Drosophile species had 77 P450 genes. Thirty of these 77 P450 genes show no sign of gain or loss in a sample of 12 Drosophila species ('1:1 orthologs') and these are enriched for P450 genes with conserved functions such as those that make the insect hormone ecdysone.