CYP2C9 is a human microsomal cytochrome P450c (CYP). Much variation in CYP2C9 levels and activity can be attributed to polymorphisms of this gene. Wild-type CYP2C9 and ten mutants were co-expressed with NADPH-cytochrome P450 reductase in Escherichia coli. The hydroxylase activities toward steroids were examined. CYP2C9.2, CYP2C9.3, CYP2C9.4, CYP2C9.16, CYP2C9.28, CYP2C9.48 and CYP2C9.52 had higher testosterone 6β-hydroxylation than CYP2C9.1. CYP2C9.4 showed higher progesterone 6β-hydroxylation activity than CYP2C9.1. CYP2C9.28 and CYP2C9.48 showed higher progesterone 11α-hydroxylation activity than CYP2C9.1. CYP2C9.48 showed higher progesterone 16α-hydroxylation activity than CYP2C9.1. CYP2C9.2, CYP2C9.3, CYP2C9.16 and CYP2C9.30 had higher estrone 16α-hydroxylation activity than CYP2C9.1. CYP2C9.3 had higher estrone 11α-hydroxylation activity than CYP2C9.1. CYP2C9.39 and CYP2C9.57 showed similar activities to CYP2C9.1. These results indicate that the substrate specificity of CYP2C9.39 and CYP2C9.57 was not changed, but CYP2C9.2, CYP2C9.3, CYP2C9.4, CYP2C9.16, CYP2C9.28, CYP2C9.30, CYP2C9.48 and CYP2C9.52 showed different hydroxylation activities toward steroids compared with CYP2C9.1.
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http://dx.doi.org/10.1002/bdd.2153 | DOI Listing |
Clin Pharmacol Ther
November 2002
Divisions of Pharmacotherapy and Cardiology, University of North Carolina at Chapel Hill, USA.
Objectives: Multiple single-nucleotide polymorphisms in the gene encoding cytochrome P450 (CYP) 2C9 have been identified, but the functional significance of the various putative defective genotypes in humans merits further study.
Methods: Using tolbutamide as a probe of CYP2C9 activity, we evaluated CYP2C9 phenotype in 15 healthy individuals expressing the CYP2C9(*)1/(*)1, (*)1/(*)2, and (*)1/(*)3 genotypes (n = 5 per group). CYP2C9 genotype was determined by polymerase chain reaction-restriction fragment length polymorphism methods.
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