title: Phenotyping and genotyping of S-mephenytoin hydroxylase (cytochrome P450 2C19) in a Shona population of Zimbabwe.
abstract: The S-mephenytoin hydroxylase has recently been identified as cytochrome P450 2C19 (CYP2C19). This enzyme metabolizes mephenytoin, diazepam, omeprazole, and citalopram and has been shown to be polymorphically distributed. One clinical implication of CYP2C19-dependent drug metabolism for persons who reside in tropical regions is in the use of the antimalarial drug chloroguanide hydrochloride, which is apparently biotransformed to its active metabolite by this isozyme. In this investigation we studied mephenytoin metabolism in 103 black Zimbabwean Shona subjects. Four were identified as poor metabolizers (4%). This prevalence is comparable to that in white subjects (2% to 5%) but lower than the 15% to 20% incidence of poor metabolizers among Oriental subjects. Of the subjects phenotyped, 84 were genotyped for the G-->A mutation in exon 5 of CYP2C19, which creates a cryptic splice site, causing the production of a nonfunctional protein. Three of the four poor metabolizers were homozygous for this mutation, whereas the fourth one was heterozygous. The G-->A mutation has been shown to predict the incidence more than 60% of poor metabolizers among white subjects and Japanese subjects, and in the current investigation we also obtained a similar relationship in the black population.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska institutet, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Masimirembwa
authors.forename: L
authors.initials: L
authors.lastname: Bertilsson
authors.forename: I
authors.initials: I
authors.lastname: Johansson
authors.forename: J A
authors.initials: JA
authors.lastname: Hasler
authors.forename: M
authors.initials: M
authors.lastname: Ingelman-Sundberg
mesh_terms: D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D065731:Cytochrome P-450 CYP2C19; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D005006:Ethnicity / Q000235:genetics; D005838:Genotype; D006801:Humans; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction; D015030:Zimbabwe
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19