细胞色素P450 2C9酶活性测定探针的分析

P450 2C9是人体中重要的药物代谢酶.P450 2C9基因编码区的多态性造成氨基酸序列的变化,主要包括P450 2C9*2和P450 2C9*3两种突变体,变异纯合子对P450 2C9底物的代谢能力明显降低.目前常用的P450 2C9的探药包括甲苯磺丁脲、华法令和洛沙坦等,各种探药在检测方法、不良反应和灵敏度方面各有优缺点.     

用基因芯片技术测定健康人群P450 2C9基因多态性

目的 探讨基因芯片技术在P450 2C9基因分型中应用的可行性，研究中国人群P450 2C9基因多态性。方法 用基因芯片技术测定169例中国健康志愿者P4502C9基因分型，并用直接测序法对结果进行验证。结果 169例中国健康志愿者中，共发现9名P450 2C9*1／*3基因型，P450 2C9*3／*3基因型1名，无P4502C9*2，P450 2C9*4和P450 2C9*5变异。结论 基因芯片法适用于中国健康人群P450 2C9基因分型研究，健康人群：P450 2C9％3等位基因频率为0．03。     

CYP2C9基因多态性对非甾体抗炎药代谢及其消化道出血的影响

非甾体抗炎药（NSAIDs）是一类具有抗炎、镇痛和解热作用的非类固醇药物,常用于治疗慢性疼痛和炎性病症。细胞色素P450 2C9酶（CYP 2C9）是NSAIDs重要的代谢酶,其基因多态性是导致个体间药物疗效及不良反应差异的重要原因之一。因此,预测CYP2C9基因与NSAIDs代谢有关的单核苷酸多态性（SNPs）可能是实现非甾体抗炎药个体化治疗的重要手段之一。本文着重介绍CYP2C9的基因多态性对CYP2C9酶介导的一些非甾体抗炎药物代谢的影响,同时介绍CYP2C9酶的两种主要基因突变类型CYP2C9*2和CYP2C9*3与非甾体抗炎药引起的消化道出血之间的相关性。     

CYP2C9基因多态性及其功能意义研究进展

细胞色素氧化酶P450 2C9（CYP2C9）是人类肝脏中一种重要药物代谢酶系统,代谢约10%临床上常用药物,特别是包括一些治疗指数较窄的药物。CYP2C9基因具有高度多态性,在基因编码区和非编码存在许多单碱基突变。到目前为止,新发现并已被命名的有CYP2C9＊7-＊30。本综述从基因结构-功能关系、突变等位基因在体内和体外的功能意义以及突变等位基因在人群和种族间的分布频率等方面总结了目前已知的突变等位基因最新研究进展。     

细胞色素P450 CYP2C9基因多态性对甲苯磺丁脲代谢动力学的影响

目的研究细胞色素P450 CYP2C9基因多态性对甲苯磺丁脲代谢动力学的影响。方法用基因芯片对137名健康志愿者进行CYP2C9基因多态性检测，将受试者分为CYP2C9野生型、杂合突变型和纯合突变型3组，用高效液相色谱法检测甲苯磺丁脲在受试者体内的药物代谢动力学参数，统计分析各组间药代动力学性质差异。结果在137名受试者中发现了9个CYP2C9*1/*3杂合型突变体和1个CYP2C9*3/*3纯合型突变体，其余为野生型个体。将9名CYP2C9*1/*3，1名CYP2C9*3/*3以及随机抽取的10名野生型个体分组，以甲苯磺丁脲为探药进行药物代谢动力学研究。结果在杂合型突变个体组以及纯合型突变个体组中，甲苯磺丁脲的代谢率显著低于对照的野生型个体组。结论CYP2C9基因多态性对甲苯磺丁脲代谢具有显著影响并呈基因剂量效应，检测突变型个体对指导临床合理用药和个体化医疗具有重要意义。     

细胞色素P_(450)2C9基因多态性与药物相互作用

目的:为指导临床合理用药、实现个体化给药提供参考。方法:本文从CYP2C9的基因多态性与代谢表型、代谢底物、代谢酶的诱导和抑制等方面,探讨CYP2C9基因多态性与药物相互作用的关系。结果与结论:CYP2C9作为一种重要的P450系氧化代谢酶,具有基因多态性,参与多种药物的氧化代谢,能被多种药物竞争性抑制,这是造成药物作用个体差异的最重要因素之一,也是发生药物相互作用的原因之一。因此对其研究具有非常重要的临床意义。     

CYP450酶特性及其应用研究进展

细胞色素P450（CYP450）是药物和其他内、外源物的主要代谢酶,本文综述了人体内参与药物代谢的几种主要代谢酶CYP3A4、CYP2D6、CYP2C9、CYP2C19、CYP2E1、CYP1A2和CYP2A6的分子生物学特征,中药对药物代谢酶的影响及药物代谢酶在临床药物治疗和新药研究过程中的应用。     

中国汉族癫痫患者CYP2C19和CYP2C9基因多态性对苯妥英钠血药浓度的影响

目的 研究中国汉族癫痫患者细胞色素P450(CYP450)2C19和2C9基因多态性对苯妥英钠血药浓度的影响.方法 用PCR-RFLP方法,分析82例患者的CYP2C19*2,*3及CYP2C9*3这3个单碱基突变位点,用荧光偏振免疫法(FPIA)测定苯妥英钠血药浓度.结果 CYP2C9*3*、CYP2C19*2及CYP2C19*3等位基因频率分别为7.3%,33.5%和3.7%.强、中间、弱代谢组间的标准化血药浓度差别显著(P=0.000).苯妥英钠血药浓度的多元线性回归中,CYP2C19*2、CYP2C19*3、CYP2C9*3这3个基因突变位点beta值分别为5.71,6.65,6.95.结论 基因突变导致苯妥英钠血药浓度升高,且与突变位点的数量有关.     

浙江沿海汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢活性关系

目的探讨浙江沿海地区汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢关系。方法采用寡核苷酸基因芯片,对浙江沿海地区汉族人群137名健康志愿者进行基因分型;选择含有突变型等位基因CYP2C9*3志愿者和部分野生型志愿者共20名参加甲苯磺丁脲药代动力学试验;统计分析不同CYP2C9基因型个体的代谢参数。结果在137名健康受试者DNA标本中发现CYP2C9*1/*3杂合突变型个体9名,CYP2C9*3/*3纯合突变个体1名,未发现CYP2C9*2、*4和*53种突变型等位基因,其中本研究受试人群中CYP2C9等位基因频率CYP2C9*1/*1占92.7%,CYP2C9*1/*3占6.6%,CYP2C9*3/*3占0.7%。药物代谢显示,CYP2C9*3纯合子个体的药物清除率显著低于CYP2C9*1纯合子个体。CYP2C9*1/*3杂合突变型个体组及1名CYP2C9*3/*3纯合型突变个体组,甲苯磺丁脲的代谢显著慢于野生型个体组。野生型(*1/*1)个体组、*1/*3杂合型突变个体组及1名*3/*3纯合型突变个体组,甲苯磺丁脲的药物代谢动力学参数差异与基因分型结果一致。结论CYP2C9多态性是甲苯磺丁脲药物代谢临床表现复杂性的主要因素,建立高效可靠的药代酶基因分型方法对CYP2C9代谢相关药物的临床个体化医疗具有一定的指导作用。     

CYP2C9、CYP2C19、CYP3A4基因多态性对磺脲类降糖药代谢的影响

磺脲类口服降糖药在人体内主要经过肝脏代谢。肝脏中的细胞色素氧化酶P450是一种重要的药物代谢酶系统,在人群中存在基因多态性,导致药物疗效和不良反应在个体间存在着较大的差异。本文将对CYP450中的几种重要的代谢酶亚型CYP2C9、CYP2C19、CYP3A4的基本结构、基因多态性、种族差异及其对磺脲类降糖药代谢的影响作一综述。     

Distribution of the major cytochrome P450 (CYP) 2C9 genetic variants in a Saudi population

Cytochrome P450 (CYP) 2C9 is responsible for the metabolism of a number of widely used drugs such as oral anticoagulants, oral antidiabetics and non-steroidal anti-inflammatory drugs. The CYP2C9 is a genetically polymorphic enzyme. The most common allele is CYP2C9*1, while CYP2C9*2 and CYP2C9*3 are the less-frequent variants. The activity of the enzyme encoded by either CYP2C9 *2 or *3 variant is lower compared with that of the CYP2C9*1. The metabolism of most of the CYP2C9 substrates decreases in varying degrees in subjects carrying the CYP2C9 *2 or *3 allele. The aim of this study was to investigate the frequencies of the major variants of the CYP2C9 in Saudi Arabians.     

Inhibitory effect of 5-fluorouracil on cytochrome P450 2C9 activity in cancer patients

Drug interactions have been reported between 5-fluorouracil and cytochrome P450 2C9 (CYP2C9) substrates, S-warfarin and phenytoin. This study was performed to determine the influence of 5-fluorouracil on cytochrome P450 2C9 (CYP2C9) activity in colorectal cancer patients (n=17) receiving 5-fluorouracil. Losartan was used as a marker to assess CYP2C9 activity. Losartan and its CYP2C9 dependent metabolite, E-3174, were determined in urine. The ratios of urinary losartan/E-3174 before and after the 5-fluorouracil treatment were compared for each patient. Genotyping was performed to detect the CYP2C9*2 and CYP2C9*3. At the end of the first cycle of 5-fluorouracil, losartan/E-3174 ratio was increased by 28.0% compared to the pre-treatment values (P=0.15). In five patients recruited for phenotyping after three 5-fluorouracil cycles, the metabolic ratio was increased significantly by 5.3 times (P=0.03). The results suggest that in most patients 5-fluorouracil inhibited CYP2C9 activity. This inhibition was more pronounced when the total administered dose increased. This finding may help explain the mechanism of interaction between 5-fluorouracil and CYP2C9 substrates.     

Catalytic activities of human cytochrome P450 2C9*1, 2C9*3 and 2C9*13

Cytochrome P450 2C9 (CYP2C9) is a geneticly polymorphic enzyme responsible for the metabolism of some clinically important drugs. CYP2C9*13 is an allele identified in a Chinese poor metabolizer of lornoxicam which has a Leu90Pro amino acid substitution. This paper reports on a study aimed at comparing the catalytic properties of CYP2C9*13 with those of the wild-type CYP2C9*1 and mutant CYP2C9*3 (Ile359Leu) in the COS-7 expression system using various substrates. CYP2C9*3 and *13 produced far lower luminescence than CYP2C9*1 in luciferin H metabolism. CYP2C9*13 exhibited an 11-fold increase in Km but no change in Vmax with tolbutamide as the substrate, a five-fold increase in Km and an 88.8% reduction in Vmax with diclofenac. These data indicate that CYP2C9*13 exhibits reduced metabolic activity toward all studied CYP2C9 substrates. The magnitude of the CYP2C9*13-associated decrease in intrinsic clearance (Vmax/Km) is greater than that associated with CYP2C9*3.     

Phenytoin metabolism by human cytochrome P450: involvement of P450 3A and 2C forms in secondary metabolism and drug-protein adduct formation.

The anticonvulsant phenytoin (5,5-diphenylhydantoin) provokes a skin rash in 5 to 10% of patients, which heralds the start of an idiosyncratic reaction that may result from covalent modification of normal self proteins by reactive drug metabolites. Phenytoin is metabolized by cytochrome P450 (P450) enzymes primarily to 5-(p-hydroxyphenyl-),5-phenylhydantoin (HPPH), which may be further metabolized to a catechol that spontaneously oxidizes to semiquinone and quinone species that covalently modify proteins. The aim of this study was to determine which P450s catalyze HPPH metabolism to the catechol, proposed to be the final enzymatic step in phenytoin bioactivation. Recombinant human P450s were coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. Novel bicistronic expression vectors were constructed for P450 2C19 and the three major variants of P450 2C9, i.e., 2C9*1, 2C9*2, and 2C9*3. HPPH metabolism and covalent adduct formation were assessed in parallel. P450 2C19 was the most effective catalyst of HPPH oxidation to the catechol metabolite and was also associated with the highest levels of covalent adduct formation. P450 3A4, 3A5, 3A7, 2C9*1, and 2C9*2 also catalyzed bioactivation of HPPH, but to a lesser extent. Fluorographic analysis showed that the major targets of adduct formation in bacterial membranes were the catalytic P450 forms, as suggested from experiments with human liver microsomes. These results suggest that P450 2C19 and other forms from the 2C and 3A subfamilies may be targets as well as catalysts of drug-protein adduct formation from phenytoin.     

Monoclonal antibodies specific and inhibitory to human cytochromes P450 2C8, 2C9, and 2C19.

Hybridomas were isolated that produce 13 monoclonal antibodies (mAbs) that are specific and highly inhibitory to members of the human P450 2C subfamily, 2C8, 2C9, 2C9*2, and 2C19. Many of the mAbs to P450 2C8, 2C9, and 2C19 are specific and exhibit potent inhibitory activity (85-95%). mAb 281-1-1 specifically binds, immunoblots, and strongly inhibits the activity of P450 2C8. mAb 763-15-5 specifically binds and strongly inhibits the activity of P450 2C9. mAb 1-7-4-8 specifically binds and strongly inhibits the activity of P450 2C19. The other mAbs bind and inhibit sets and subsets of the P450 2C family. The single and the combinatorial use of the mAbs can "reaction phenotype", i.e., determine the metabolic contribution and interindividual variation of a P450 isoform for the metabolism of a drug or nondrug xenobiotic in human liver microsomes. The utility of the mAb-based analytic system was examined with the model substrates Taxol (paclitaxel), diazepam, tolbutamide, diclofenac, mephenytoin, and imipramine. The mAb system can identify drugs metabolized by a common P450 or several P450s and polymorphic P450s. The mAb system identifies drugs or drug metabolic pathways that are catalyzed by a single P450 and thus may be used for in vivo phenotyping. The mAb system can identify whether a particular drug is metabolized by a single P450 that may exhibit polymorphic expression in humans. The mAb system offers large potential for studies of cytochrome P450 function useful in drug discovery and reduces the possibility of adverse drug reactions due to polymorphisms and drug interactions.     

High frequency of mutations related to impaired CYP2C9 metabolism in a Caucasian population.

OBJECTIVE: To search for ethnic variability in the impact of cytochrome P450 2C9 (CYP2C9) polymorphism. METHODS: CYP2C9 allelic variants related to impaired CYP2C9 metabolism were analysed in genomic DNA from 157 Spanish healthy subjects using amplification-restriction and sequencing procedures. RESULTS: The frequency for CYP2C9 mutated alleles is higher among the Spanish subjects analysed than that reported for other Caucasian individuals: CYP2C9*2, 0.143 and CYP2C9*3, 0.162 (P = 0.0001). Nearly 10% of the individuals studied are expected to metabolise deficiently CYP2C9 substrates. CONCLUSION: In some Caucasian populations the impact of the CYP2C9 polymorphism may be much higher than that estimated from genotyping studies published to date.     

Human cytochrome p450 enzyme specificity for bioactivation of safrole to the proximate carcinogen 1'-hydroxysafrole

In the present study, the cytochrome P450 mediated bioactivation of safrole to its proximate carcinogenic metabolite, 1'-hydroxysafrole, has been investigated for the purpose of identifying the human P450 enzymes involved. The 1'-hydroxylation of safrole was characterized in a variety of in vitro test systems, including Supersomes, expressing individual human P450 enzymes to a high level, and microsomes derived from cell lines expressing individual human P450 enzymes to a lower, average human liver level. Additionally, a correlation study was performed, in which safrole was incubated with a series of 15 human liver microsomes, and the 1'-hydroxylation rates obtained were correlated with the activities of these microsomes toward specific substrates for nine different isoenzymes. To complete the study, a final experiment was performed in which pooled human liver microsomes were incubated with safrole in the presence and absence of coumarin, a selective P450 2A6 substrate. On the basis of the results of these experiments, important roles for P450 2C9*1, P450 2A6, P450 2D6*1, and P450 2E1 were elucidated. The possible consequences of these results for the effects of genetic polymorphisms and life style factors on the bioactivation of safrole are discussed. Polymorphisms in P450 2C9, P450 2A6, and P450 2D6, leading to poor metabolizer phenotypes, may reduce the relative risk on the harmful effects of safrole, whereas life style factors, such as the use of alcohol, an inducer of P450 2E1, and barbiturates, inducers of P450 2C9, and polymorphisms in P450 2D6 and P450 2A6, leading to ultraextensive metabolizer phenotypes, may increase the relative risk.     

Cytochrome P450 2C9 polymorphisms: a comprehensive review of the in-vitro and human data

The discovery of six distinct polymorphisms in the genetic sequence encoding for the cytochrome P450 2C9 (CYP2C9) protein has stimulated numerous investigations in an attempt to characterize their population distribution and metabolic activity. Since the CYP2C9*1, *2 and *3 alleles were discovered first, they have undergone more thorough investigation than the recently identified *4, *5 and *6 alleles. Population distribution data suggest that the variant *2 and *3 alleles are present in approximately 35% of Caucasian individuals; however, these alleles are significantly less prevalent in African-American and Asian populations. In-vitro data have consistently demonstrated that the CYP2C9*2 and *3 alleles are associated with significant reductions in intrinsic clearance of a variety of 2C9 substrates compared with CYP2C9*1; however, the degree of these reductions appear to be highly substrate-dependent. In addition, multiple in-vivo investigations and clinical case reports have associated genotypes expressing the CYP2C9*2 and *3 alleles with significant reductions in both the metabolism and daily dose requirements of selected CYP2C9 substrates. Individuals expressing these variant genotypes also appear to be significantly more susceptible to adverse events with the narrow therapeutic index agents warfarin and phenytoin, particularly during the initiation of therapy. These findings have subsequently raised numerous questions regarding the potential clinical utility of genotyping for CYP2C9 prior to initiation of therapy with these agents. However, further clinical investigations evaluating the metabolic consequences in individuals expressing the CYP2C9*2, *3, *4, *5, or *6 alleles are required before large-scale clinical genotyping can be recommended.     

Catalytic activities of human cytochrome P450 2C9*1, 2C9*3 and 2C9*13

Cytochrome P450 2C9 (CYP2C9) is a geneticly polymorphic enzyme responsible for the metabolism of some clinically important drugs. CYP2C9*13 is an allele identified in a Chinese poor metabolizer of lornoxicam which has a Leu90Pro amino acid substitution. This paper reports on a study aimed at comparing the catalytic properties of CYP2C9*13 with those of the wild-type CYP2C9*1 and mutant CYP2C9*3 (Ile359Leu) in the COS-7 expression system using various substrates. CYP2C9*3 and *13 produced far lower luminescence than CYP2C9*1 in luciferin H metabolism. CYP2C9*13 exhibited an 11-fold increase in K_m but no change in V_max with tolbutamide as the substrate, a five-fold increase in K_m and an 88.8% reduction in V_max with diclofenac. These data indicate that CYP2C9*13 exhibits reduced metabolic activity toward all studied CYP2C9 substrates. The magnitude of the CYP2C9*13-associated decrease in intrinsic clearance (V_max/K_m) is greater than that associated with CYP2C9*3.