细胞色素P450与肿瘤

本文综棕了细胞色素Ｐ４５０同工酶与致癌物代谢、与抗癌药的相互作用以及化的关系,并对调控Ｐ４５０同工酶以防治肿瘤的策略进行了论述。由于Ｐ４５０同工酶具有多态性、工物特异性及可诱导性的特点,在调控Ｐ４５０同工酶以防治肿瘤的问题上,针对不同人群、不同疾病状况及不同用药方案可能需采取抑制或诱导的不同策略。     

细胞色素P450基因多态性与药物代谢研究进展

细胞色素P450（cytochrome P450,CYP450）在人体药物代谢过程中起着非常重要的作用并参与代谢80%以上的临床药物。由于CYP450在不同种族和不同人群中存在基因多态性,从而造成药物反应的个体差异,一度成为药物基因组学研究的热点。通过查阅国外相关文献,综述了近年来关于CYP1A2、CYP2C9、CYP2C19、CYP2D6和CYP3A4五种主要的药物代谢酶的基因多态性和药物代谢的研究进展,为临床指导个体化用药、避免药物不良反应和新药研发提供科学参考依据。     

生物转化酶类基因多态性与肿瘤易感性

肿瘤易感性一直是肿瘤研究的重要课题,而生物转化酶类的细胞色素P450（CYP450）和谷胱甘肽转硫酶（GST）等由于其对环境致癌物的生物转化作用决定了个体对肿瘤的易感程度。通过介绍其中的CYP1A1,CYP2D6,CYP2E1,GSTM1和GSTT1等的基因多态性及其与机体易患肿瘤的关系,揭示了生物转化酶基因多态性在肿瘤易感性中的作用,国内外的研究结果表明,CYP1A1基因多态性与肺癌的发生,CYP2E1基因多态性与食管癌的易感性均密切相关,GSP的基因多态性虽然与多种肿瘤的易感性有关联但研究结果有的互相矛盾,提示机体肿瘤发生机理的复杂性,由于环境致癌物在体内需经一系列的生物转化而产生生物学效应,因而生物转化酶类基因多态性的联合作用在肿瘤的易感中显得尤为重要。     

昆虫细胞色素P450研究:P450基因

细胞色素P450广泛存在于生物界,它因参与许多外来物质和内源性物质的代谢而具有十分重要的作用［1－5］细胞色素P450的研究大约有50多年的历史[3]。60年代的工作主要是对这一血红素蛋白的生物化学和生物物理学特征的了解以及膜结合P450酶系的酶学功能[3]。70年代的研究集中在细胞色素P450酶系的分离纯化及其活性的重组。纯化P450的成功证明了许多P450在物理学和酶学特征方面的不同,也为制备抗体及利用抗体来确定某种P450的存在与数量以及抑制特定P450的酶活性提供了手段,使进一步阐明P450的反应机制成为可能。80年代分子生物学技术的…     

细胞色素P4501B1基因多态性与乳腺癌易感性研究进展

细胞色素P450（cytochrome,CYP）1B1是P450超基因家族酶系的一个重要成员,广泛分布于肝外组织,其代谢受到外源性致癌物、雌激素等多种因素的调控。该基因存在遗传多态性,艮前已对CYP1B1基因多态性与乳腺癌易感性进行了多项研究。本文就CYP1B1基因的多态性、调控机制及其与乳腺癌的关系进行了综述。     

人类细胞色素P450与药物氧化代谢遗传多态性分子机制的研究现状

近年,在表型及基因型上均发现存在药物氧化代谢多态性,特别是对于人类细胞色素Ｐ４５０氧化酶与药氧化代谢遗传多态性的关系进行了深入的研究。有关ＣＹＰ２Ｄ６、ＣＹＰ２Ｃ１９等的突变已大多被鉴定;ＣＹＰ１Ａ１、ＣＹＰ１Ａ２等在表型存在多态性而确切的遗传机制尚不清楚。     

昆虫细胞色素P450的研究:P450基因的进化

80年代分子生物学方法被用于分离和鉴定特定P450的CDNA或基因组克隆［‘］,至今已知的P450基因包括70个基因家族、127个亚家族的40O多个,基因序列的数量还在迅速增加I’］。不同P450间的进化关系在一些综述中都有涉及［”’,‘］,本文介绍这一主题的一些主要观点,重点放在P450功能的进化及其机制。亚细胞色素P450的基本特征及其分类与命名所有细胞色素P450具有一非共价结合的血红素和环绕高度保守的半跳氨酸的一段26氨基残基的保守序列,这一半跳氨酸提供血红素铁的第5个配体（ligand）。当血红素铁接受电子被还原后再与CO结合产…     

唐鱼细胞色素P450 1A基因cDNA克隆及分析

鱼类细胞色素P450 1A(CYP1A)基因作为一种有效的生物标志物已被广泛应用于环境污染物的评价,唐鱼在水环境污染监测中有较好的应用优势,为建立唐鱼在水环境的检测的有效生物标志物方法,本研究对其CYP1A基因进行克隆。利用RT-PCR法扩增出一条651bp的唐鱼CYP1A基因cDNA片段,该片段与其他物种的CYP1A基因具有很高的相似性。在此基础上进行5'端扩增和3'RACE获得了唐鱼CYP1A基因的全长cDNA序列,其长度为2177bp,其中编码区长1566bp,编码521个氨基酸残基组成的蛋白质,推测该蛋白质分子量大小为58.5kDa,理论等电点为5.65。所得序列具有CYP1A分子的主要特征和功能域,包括亚铁血红素结合区、酶功能所需的精氨酸密码子和终止密码子。推导出的氨基酸序列与斑马鱼、底鳉、虹鳟、大西洋鳕、人、鼠等脊椎动物同源性分别为87.7%、70.1%、76.2%、62.2%、54.5%、55.7%。     

细胞色素P450：肿瘤研究中的新热点

细胞色素P450（CYP450）是体内重要的Ⅰ相代谢酶,与许多前致癌物和致癌物的活化有关。CYP450是目前肿瘤研究中新的热点之一。深入研究CYP450在肿瘤发生、发展过程中的作用机制及基因多态性与肿瘤易感性的关系,对肿瘤防治有积极作用。现就近年来CYP450在肿瘤领域的研究进展进行综述。     

细胞色素P450：肿瘤研究中的新热点

细胞色素P450(CYP450)是体内重要的Ⅰ相代谢酶,与许多前致癌物和致癌物的活化有关。CYP450是目前肿瘤研究中新的热点之一。深入研究CYP450在肿瘤发生、发展过程中的作用机制及基因多态性与肿瘤易感性的关系,对肿瘤防治有积极作用。现就近年来CYP450在肿瘤领域的研究进展进行综述。     

Induction of Two Forms of Eel Cytochrome P450 1A Genes by 3-Methylcholanthrene

In eel (Anguilla japonica), exposure to polyaromatic hydrocarbons such as 3-methylcholanthrene leads to induction of two CYP1A enzymes, CYP1A1 and CYP1A6. We studied the time course and tissue specificity of induction of messenger RNAs for CYP1A1 and CYP1A6 in eel by administering 3-methylcholanthrene intraperitoneally. In both cases, the drug induced a rapid increase of mRNAs and biphasic expression. In the liver, mRNA levels of CYP1A1 and CYP1A6 increased 22-fold at 3 hours and 27-fold at 6 hours after the administration, respectively, showing initial peaks in the induction. After the initial inductions, mRNA levels decreased unexpectedly. Following these temporary decreases, the mRNA levels again increased and reached levels that were 35 and 41 times the basal levels at 24 hours after administration, respectively. CYP1A1 and CYP1A6 resembled each other also in the tissue specificity of gene expression; the expression levels were liver ≫ gill > intestine > kidney. The rapid induction, the biphasic expression, and the tissue-specific expression were common features of gene expression in CYP1A1 and CYP1A6 and may come from common structures of the regulatory regions of the two genes. Received December 7, 1998; accepted February 15, 1999     

鸡细胞色素P450 1A5的原核表达与活性重组

旨在对鸡细胞色素P450 1A5(CYP1A5)蛋白进行体外功能研究,采用大肠杆菌系统进行CYP1A5的异源表达。以鸡的cDNA为模板,扩增出CYP1A5基因,将该基因的N端编码区进行修饰,并连接到pCW载体中构建His-CYP1A5,经IPTG诱导在大肠杆菌中表达。经CO-差示光谱检测,所获得的His-CYP1A5具有典型的P450吸收峰。该蛋白与细胞色素P450还原酶(CPR)进行体外重组,构成的重组酶系表现出乙氧基试卤灵-O-脱乙基酶活性。结果表明,所采用的表达策略可以成功产生出具有催化活性的鸡细胞色素P450 1A5(CYP1A5)蛋白。     

上海交通大学附属第一人民医院中心实验室

目的：研究内蒙古地区汉族非吸烟人群和吸烟人群中,细胞色素P4501A1（cytochromc P4501A1,CYP1A1）基因MspI酶切位点多态性与慢性重度牙周炎（chronic severe periodontitis,CP）易感性的关系。方法：对50例CP患者和51例正常对照者按吸烟情况进行分组。用聚合酶链反应-限制性片段长度多态性技术（PCR-RFLP）,检测研究人群中CYP1A1基因3’端MspI酶切位点的3种基因型（A,B,C）的分布频率。结果：不考虑吸烟情况下,MspI基因型C在病例组和对照组中各占20％和13．7％,基因型A在两组中分别占42％和47．1％,基因型B在两组中分别占38％和39．2％,各基因型在两组间比较差异无显著性（P〉0．05）。但在吸烟组MspI C型者患慢性重度牙周是的危险性（OR）是其他基因型的5倍（95％可信限：1．34218．62）。结论：MspI C型可能是吸烟者慢性重度牙周炎易感性的遗传标志。     

Cytochrome P450 in living donor liver transplantation

Cytochrome P450 metabolizes many drugs in the liver. Three genotypes of CYP2C19 with extensive, intermediate, and poor metabolizing activity, respectively, have been identified in peripheral blood of transplant recipients and new liver grafts in living donor liver transplantation (LDLT). The expression of the final genotype in liver graft biopsies depends on the donor, whereas the expression in peripheral blood mononuclear cells depends on the recipient. The metabolizing isoenzyme of the major anti-rejection agents passes through CYP3A4, CYP3A5 and MDR1, which have also been identified to have similar biological characteristics as genotype of CYP2C19 in liver tissue. Recently, pyrosequencing has been used to investigate the expressions of different genotypes in liver grafts in LDLT. This review focuses on recent findings regarding the biological expressions of the CYP2C19, CYP3A4, CYP3A5 and MRD1 genotypes in liver grafts before and after LDLT. The application of pyrosequencing may be beneficial in further research on liver transplantation. Laser capture microdissection of hepatocytes in liver grafts may be a direction for future research.     

Exploration of Natural and Artificial Sequence Spaces: Towards a Functional Remodeling of Membrane-bound Cytochrome P450

Abstract

Two complementary methods are described that associate in vitro and in vivo steps to generate sequence diversity by segment directed saturated mutagenesis and family shuffling. A high-throughput DNA chip-based procedure for the characterization and potentially the equalization of combinatorial libraries is also presented. Using these approaches, two combinatorial libraries of cytochrome P450 variants derived from the CYP1A subfamily were constructed and their sequence diversity characterized. The results of functional screening using high-throughput tools for the characterization of membrane P450-catalyzed activities, suggest that the 204–214 sequence segment of human CYP1A1 is not critical for polycyclic aromatic hydrocarbon recognition, as was hypothesized from previous data. Moreover, mutations in this segment do not alter the discrimination between alkoxyresorufins, which, for all tested mutants, remained similar to that of wild-type CYP1A1. In contrast, the constructed CYP1A1–CYP1A2 mosaic structures, containing multiple crossovers, exhibit a wide range of substrate preference and regioselectivity. These mosaic structures also discriminate between closely related alkoxyresorufin substrates. These results open the way to global high-throughput analysis of structure–function relationships using combinatorial libraries of enzymes together with libraries of structurally related substrates.     

Cytochrome P450 1A1 gene polymorphisms and digestive tract cancer susceptibility: a meta‐analysis

Cytochrome P450 1A1 (CYP1A1) is a phase I enzyme that regulates the metabolism of environmental carcinogens and alter the susceptibility to various cancers. Many studies have investigated the association between the CYP1A1 MspI and Ile462Val polymorphisms and digestive tract cancer (DTC) risk in different groups of populations, but their results were inconsistent. The PubMed and Embase Database were searched for case–control studies published up to 30th September, 2015. Data were extracted and pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the relationship. Totally, 39 case–control studies (9094 cases and 12,487 controls) were included. The G allele in Ile/Val polymorphism was significantly associated with elevated DTC risk with per‐allele OR of 1.24 (95% CI = 1.09–1.41, P = 0.001). Similar results were also detected under the other genetic models. Evidence was only found to support an association between MspI polymorphism and DTC in the subgroups of caucasian and mixed individuals, but not in the whole population (the dominant model: OR = 1.19, 95% CI = 0.94–1.91, P = 0.146). In conclusion, our results suggest that the CYP1A1 polymorphisms are potential risk factors for DTC. And large sample size and well‐designed studies with detailed clinical information are needed to more precisely evaluate our founding.