Metazoan cytochrome P450 evolution

There are 37 cytochrome P450 families currently identified in animals. The concept of higher order groupings of P450 families called P450 CLANS is int roduced. The mammalian CYP3 and CYP5 families belong to the same clan as in sect. CYP6 and CYP9. All mitochondrial P450s seem to belong to the same dan . Lack of mitochondrial P450s in C. elegans suggests that mitochondrial P45 0s probably arose from the mistargeting of a microsomal P450 after the coel omates diverged from acoelomates and pseudocoelomates. Different taxonomic groups appear to have recruited different ancestral P450s for expansion as they evolved, since each major taxon seems to have one large cluster of P45 0s. In insects, this cluster derives from the ancestor to the CYP4 family. Vertebrates and C. elegans may have used the same ancestor independently to generate the CYP1, 2, 17, and 21 families in vertebrates and a large disti nctive dan with 45 genes in C. elegans. (C) 1998 Elsevier Science Inc. All rights reserved.