ABSTRACT
Human cytochrome P450 2C9 is a highly polymorphic enzyme that is required for drug and xenobiotic metabolism. Here, we studied eleven P450 2C9 genetic variants—including three novel variants F69S, L310V, and Q324X—that were clinically identified in Korean patients. P450 2C9 variant enzymes were expressed in Escherichia coli and their bicistronic membrane fractions were prepared The CO-binding spectra were obtained for nine enzyme variants, indicating P450 holoenzymes, but not for the M02 (L90P) variant. The M11 (Q324X) variant could not be expressed due to an early nonsense mutation. LC-MS/MS analysis was performed to measure the catalytic activities of the P450 2C9 variants, using diclofenac as a substrate. Steady-state kinetic analysis revealed that the catalytic efficiency of all nine P450 2C9 variants was lower than that of the wild type P450 2C9 enzyme. The M05 (R150L) and M06 (P279T) variants showed high k(cat) values; however, their K(m) values were also high. As the M01 (F69S), M03 (R124Q), M04 (R125H), M08 (I359L), M09 (I359T), and M10 (A477T) variants exhibited higher K(m) and lower k(cat) values than that of the wild type enzyme, their catalytic efficiency decreased by approximately 50-fold compared to the wild type enzyme. Furthermore, the novel variant M07 (L310V) showed lower k(cat) and K(m) values than the wild type enzyme, which resulted in its decreased (80%) catalytic efficiency. The X-ray crystal structure of P450 2C9 revealed the presence of mutations in the residues surrounding the substrate-binding cavity. Functional characterization of these genetic variants can help understand the pharmacogenetic outcomes.
Subject(s)
Humans , Codon, Nonsense , Cytochrome P-450 Enzyme System , Cytochromes , Diclofenac , Escherichia coli , Holoenzymes , Membranes , Metabolism , PharmacogeneticsABSTRACT
@#Warfarin is one of the most frequently prescribed oral anticoagulant. Many researches have shown that the genotypes have been strongly associated with warfarin maintenance doses. Especially, it has been accepted in academia that cytochrome P450 2C9 (CYP2C9) and vitamin K epoxide reductase complex 1 subunit (VKORC1) could affect the warfarin maintenance doses. There are also many other genotypes that were reported to be related to warfarin doses, but the results have been in controversial so far. The studies found that the dose formula which contained the genetic factors and clinical information could accurately predict the maintenance dose of warfarin, however, its usefulness is suspected due to the inconsistent results of clinical trials. Large-sample and multi-center studies are necessary to verify the specific effects of gene and non-gene factors to warfarin dose; at the same time, testing constructed models or building new models help to improve the explained percentages of individual differences.
ABSTRACT
Objective To use the fluorescence PCR‐melting curve method to detect CYP2C9 and VKORC1 gene polymorphism in Xinjiang Hui population ,to analyze their gene distribution and gene mutation frequency ,and to evaluate the clinical applicability of the fluorescence PCR‐melting curve method .Methods The fluorescence PCR‐melting curve method and sequencing method were adopted to contrastively detect CYP2C9*2 ,CYP2C9*3 and VKORC1(‐1639G/A)gene polymorphism .Results Among detected 228 Xinjiang Hui individuals ,199 cases of CYP2C9*1/*1 ,2 cases of CYP2C9*1/*2 ,26 cases of CYP2C9*1/*3 and only 1 case of CYP2C9*3/*3 were detected ,no case of CYP2C9*2/*2 and CYP2C9*2/*3 was detected .Two kinds of allele G and A were detected for VKORC1(‐1639G/A) ,in which VKORC1‐1639G/G type was detected in 2 cases ,VKORC1‐1639G/A type was detected in 39 cases and VKORC1‐1639A/A type was detected in187 cases ,compared with the sequencing method ,the results of the fluorescence PCR‐melting curve method were completely consistent .Conclusion Xinjiang Hui population also has CYP2C9 gene *2 ,*3 loci and VKORC1 gene(‐1639G/A) locus polymorphism ,their occurrence frequency has a certain difference with Xingjiang Uygur and other regional populations ,the adopted fluorescence PCR‐melting curve method used in the gene polymorphism detection can meet clinical detection requirements .
ABSTRACT
Aim To explore the effect of genetic poly-morphisms of POR on the stable warfarin maintenance doses in Han Chinese patients receiving mechanical heart valve replacement. Methods The association between POR gene polymorphisms and warfarin doses of 185 Han Chinese patients were investigated through ANOVA or t test. SNPs of POR and VKORC1 were de-tected by Sequenom? DNA MassArray genotyping method. CYP2C9*3 was genotyped by polymerase chain reaction-restriction fragment length polymorphism method ( PCR-RFLP ) . Patients ’ clinical characteris-tics, INR value and daily dose were obtained from their medical records. Statistical analysis was performed by SPSS 21. 0 software. Results No mutant carriers of POR rs17148944 , POR rs56256515 and rs72553971 were found in this study. The genotype frequencies of other SNPs were in accordance with Hardy-Weinberg e-quilibrium. In the group of patients with CYP2C9*1*1 , the mutant type carriers ( T carriers ) of POR rs17685 had a significantly higher dose than CC carri-ers(3. 50 ± 1. 07) mg·d-1 vs (3. 14 ± 0. 94) mg· d-1,P =0. 03. Also, in the group of patients with CYP2 C9*1*1 and VKORC1 rs9934438 G allele carri-ers, the mutant type carriers ( T carriers ) of POR rs17685 had a significantly higher dose than CC carri-ers(4. 76 ± 0. 90) mg·d-1 vs (4. 08 ± 1. 03) mg· d-1 ,P=0. 04. No significant difference was found in different genotypes of POR rs2868177 . Conclusion These results illustrate that POR rs17685 T carrier is closely associated with a higher warfarin maintenance dose, suggesting that this SNP is useful for clinical guidance of warfarin.