Cloning and sequence determination of a complementary DNA related to human liver microsomal cytochrome P-450 S-mephenytoin 4-hydroxylase.

A cDNA sequence related to the human cytochrome P-450 responsible for S-mephenytoin 4-hydroxylation (P-450MP) has been isolated from a human liver bacteriophage lambda gt11 library with antibodies specific for P-450MP. The total length of the cDNA is 2.5 kilobases (kb), of which there is a 1.6-kb EcoRI fragment coding for all but five amino acids corresponding to the N-terminus of the protein and including a small noncoding region at the 3' end. This 1.6-kb fragment has been sequenced and used as a probe to analyze human genomic DNA and liver RNA. The sequence shows extensive sequence similarity with that of rabbit liver cytochrome P-450 progesterone 21-hydroxylase [Tukey, R. H., Okino, S., Barnes, H., Griffin, K. J., & Johnson, E. F. (1985) J. Biol. Chem. 260, 13347-13354], and this cDNA, like the rabbit clone, appears to be part of a multigene family. At least two liver mRNA species, 2.2 kb and 3.5 kb, hybridize to the cDNA sequence. The cloning of this gene should aid in analyzing the molecular basis for the genetic polymorphism of S-mephenytoin 4-hydroxylation reported in humans.