Genetic findings and functional studies of human CYP3A5 single nucleotide polymorphisms in different ethnic groups.
OBJECTIVE
Genetic polymorphisms of cytochromes P450 (CYPs) are a principal reason for inter-individual variations in the metabolism of therapeutic drugs and environmental chemicals in humans. The present study identifies 34 single nucleotide polymorphisms (SNPs) of CYP3A5 including 27 previously unidentified SNPs by direct sequencing of the exons, intron-exon junctions and 5'-upstream region of CYP3A5 from 92 racially diverse individuals (24 Caucasians, 24 Africans, 24 Asians, and 20 individuals of unknown racial origin).


RESULTS
Four new CYP3A5 SNPs produced coding changes: R28C, L82R, A337T, and F446S. CYP3A5 R28C occurred in African populations (allelic frequency of 4%). CYP3A5 A337T occurred in Asians (2% allelic frequency), CYP3A5 L82R (occurred in the racially unidentified group) and CYP3A5 F446S (identified in Caucasians with a 2% allelic frequency) were on an allele containing the splice change g.6986A>G known as CYP3A5*3. The newly identified allelic proteins were constructed by site-directed mutagenesis, expressed in Escherichia coli and purified. CYP3A5 L82R was expressed only as denatured CYP420, suggesting it may be unstable. CYP3A5*1 exhibited the highest maximal clearance for testosterone followed by CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S. CYP3A5*1 exhibited a higher V(max) for nifedipine oxidation than CYP3A5 A337T > CYP3A5 R28C >> CYP3A5 F446S. CYP3A5 A337T and CYP3A5 R28C exhibited a 42-64% lower V(max) for nifedipine oxidation than CYP3A5*1. CYP3A5 F446S exhibited a > 95% decrease in the intrinsic clearance for both 6beta-hydroxytestosterone and nifedipine oxidation.


CONCLUSIONS
This study identifies four new potentially defective coding alleles. CYP3A5 F446S is predicted to be more catalytically defective than the splice change alone.
Lee
Su-Jun
SJ
Human Metabolism Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
Usmani
Khawja A
KA
Chanas
Brian
B
Ghanayem
Burhan
B
Xi
Tina
T
Hodgson
Ernest
E
Mohrenweiser
Harvey W
HW
Goldstein
Joyce A
JA
D000483:Alleles; D001483:Base Sequence; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D017931:DNA Primers; D018076:DNA, Complementary; D004926:Escherichia coli / Q000235:genetics; D005006:Ethnicity / Q000235:genetics*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009543:Nifedipine / Q000493:pharmacokinetics; D020641:Polymorphism, Single Nucleotide; D013739:Testosterone / Q000493:pharmacokinetics
D017931:DNA Primers; D018076:DNA, Complementary; D013739:Testosterone; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; D009543:Nifedipine