Kirischian, N., A.G. McArthur, C. Jesuthasan, B. Krattenmacher, & J.Y. Wilson. 2010. Phylogenetic and functional analyses of the cytochrome P450 families 2 and 4. Oral presentation at the 10th International Symposium on P450 Biodiversity and Biotechnology, Woods Hole, Massachussetts.In vertebrates, the CYP2 family is one of the largest and most diverse, with more than 20 subfamilies, and plays an important role in mammalian drug metabolism. The CYP4 family metabolizes endogenous compounds such as fatty acids. Both CYP2 and CYP4 families have uncertain phylogenetic relationships amongst the vertebrate subfamilies. To better understand CYP2 and CYP4 diversity, phylogenetic analyses of protein sequences were completed. Sequences from mammalian (human, cow, dog), actinopterygian (fugu, zebrafish, medaka, stickleback), avian (chicken) and amphibian (frog) genomes were targeted in our analyses. Two CYP2 subfamilies (CYP2R and CYP2U) pre-date vertebrate diversification, while all other subfamilies originated during vertebrate diversification. The CYP4V subfamily, which is found in both vertebrate and invertebrate species, was the most ancestral subfamily present in vertebrates. Frog CYP4T genes were clustered between the mammalian CYP4B and actinopterygian CYP4Tgenes; the nomenclature of the frog genes may need to be revisited. Analysis of site-specific evolution indicates that some substrate recognition sites (SRS) previously proposed for CYP genes do not have elevated rates of evolution in either CYP2 or CYP4 subfamilies, suggesting that these regions of the protein are not necessarily important in recognition of CYP substrates. In both CYP2 and CYP4 analyses, site-specific evolutionary rates were either highly divergent or no significant divergence across the whole protein. For example, comparisons with the CYP4X subfamily had high functional divergence across the whole protein yet the majority of pairwise comparisons with mammalian CYP4F22 genes had no significant functional divergence. Type II functional divergence analyses identified multiple residues in the active site of CYP2F, CYP2A and CYP2B proteins that have undergone radical biochemical changes and may be functionally important.
