细胞色素P450酶催化反应动力学研究进展

细胞色素P450是内质网膜上混合功能氧化酶系统的末端氧化酶,在生物体内分布广泛,主要催化机体内源和外源性物质在体内的氧化反应.细胞色素P450种类的多样性、催化反应类型的多样性以及底物的广谱性使其成为自然界最具催化作用的生物催化剂.在临床药物的生物学转化中,它参与大部分药物的生物氧化,因此具有重要的生物学意义.本文主要对细胞色素P450的催化反应机理,尤其是细胞色素P45催化下乙醇氧化的反应机理,及其在药代动力学方面的研究进行了综述.     

昆虫P-450基因特点及研究现状

细胞色素P－450在生物体内的重要作用和功能正日益受到人们的关注,尤其是在药物代谢和致癌机理的研究中引起了人们的广泛兴趣。人们对P－450的研究已深入到基因水平,目前被克隆测序的P－450cDNA已多达300种以上,而且不断有其在体外表达的报道。这主要基于把人、鼠、兔、猴、狗等高等动物作为研究对象[1,2]。虽然,人们很早就认识到P－450在昆虫体内代谢外源性物质和产生抗药性过程中的重要作用,但对昆虫P－450基因的研究起步较晚,目前尚只对少数几种昆虫的P－450研究深入到基因水平。本文简要介绍近年来昆虫P－450基因的研究现状…     

原核生物细胞色素P450酶系及其应用

细胞色素P450酶系广泛分布于各种生物中,它们通常由一组基因超家族编码并含有血红素,能够催化一系列化学反应,具有多种生物学功能。特别是原核生物P450酶在催化内源性和外源性化合物的反应中具有重要的工业生产应用价值,成为近年来P450酶系研究的热点。本文对近年来原核生物P450酶系的重组表达和生物催化领域的研究进展进行综述。     

阿部鲻鰕鯱P450 1A1克隆与分析

细胞色素P450(Cytochrome P450,简称CYP)是生物体内广泛存在的一类重要的代谢酶,它参与包括内源性物质和多种外源性物质(包括药物)在内的各类物质的代谢和转化.     

细胞色素P450酶与微生物药物创制北大核心CSCD

细胞色素P450酶广泛存在于动植物和微生物体内,具有底物结构多样性和催化反应类型多样性,在天然产物生物合成中扮演重要作用。P450酶可在温和条件下高选择性地催化结构复杂有机化合物中惰性C-H键的氧化反应,具备化学催化剂难以比拟的优势,因此在微生物制药领域具有广阔的应用空间。本文综述了参与天然产物生物合成的P450酶近年来的研究进展;P450酶的酶工程改造、生物转化实践及其在微生物药物创制方面的应用现状;探讨了P450酶的工业应用瓶颈及其解决途径;并对P450酶未来的应用前景进行了展望。     

昆虫细胞色素P450与抗药性关系研究进展

细胞色素P450单加氧酶系是一类广泛分布于生物有机体中的重要酶系,它能够代谢多种内源性物质和外源性物质,因其生物学的重要性,一直是生物学领域研究的一个重要对象.本文综述了昆虫细胞色素P450目前的一些研究进展,介绍了其与昆虫抗药性之间的关系,并阐述了细胞色素P450介导抗性的分子基础.     

细胞色素P450基因的命名及其基因表达的调控

<正> 作者于1990年对细胞色素P450的分子特征和光谱特征、P450的多样性、诱导性及其分子机理、以及P450在昆虫的适应性和抗药性中的作用作了介绍。如前二文所述,在动物、植物、微生物等生物体内都存在着许多种不同的细胞色素P450(以下简称P450)。这些含血红素的蛋白能催化许多种不同亲脂底物的加单氧反应,其氧化产物可能成为无毒物质,     

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P450催化二甲基亚硝胺C-H键羟基化机理的理论研究进展

细胞色素P450是广泛存在于哺乳动物微粒体和线粒体内的一类亚铁血红素—硫醇盐蛋白的超家族。它参与内源性物质和包括药物、环境化合物在内的外源性物质的代谢。其代谢机理引起人们的极大关注,同时也存在诸多挑战。通过对不同底物代谢机理的研究有助于人们深入认识P450的结构及其催化机理,还可以为物质的体内代谢提供理论指导。本文主要对P450的催化氧化机制,二甲基亚硝胺在细胞色素P450作用下的代谢机理研究进展及P450的活性氧化物等方面的研究进行了综述。     

细胞色素P450与除草剂代谢

细胞色素P450是广泛存在于生物中的一类具有混合功能的血红素氧化酶。P450对除草剂代谢的机制及反应类型是多样的,与除草剂代谢相关的P450基因的植物转基因研究得到了具有不同除草剂抗性的转基因植物。文章就这方面的研究进展作介绍。     

Specificity of Isatin Interaction with Cytochromes P450

Cytochrome P450-dependent monooxygenase systems exist basically in all living organisms, where they perform various important functions. The coordinated functioning of these systems involves many proteins participating in different protein-protein interactions (PPI). Previously, we have found that the endogenous non-peptide bioregulator isatin (indoledione-2,3), synthesized from indole by means of certain cytochromes P450 (e.g. P450 2E1, P450 2C19, P450 2A6) regulates affinity of some PPI. In this study, an attempt has been undertaken to register a direct interaction of isatin with a set of different proteins related to the functioning of cytochrome P450-dependent monooxygenase systems: five isoforms of cytochromes P450, two isoforms of cytochrome b₅, cytochrome P450 reductase, adrenodoxin, adrenodoxin reductase and ferrochelatase. The study has shown high affinity specific binding of isatin only to cytochromes P450 (the equilibrium dissociation constant (K_d) is about 10^–8 M).     

棉酚和烟碱对棉铃虫的生长和细胞色素P-450单加氧酶活性的影响

以人工饲料添加法测定了 0 5%的棉酚和烟碱对棉铃虫的生长和细胞色素P 4 50单加氧酶 (简称P 4 50酶系 )活性的影响。研究结果显示 ,在测定浓度下 ,高龄棉铃虫短期取食含棉酚和烟碱的人工饲料后 ,对幼虫的生长没有显著影响 ,由此表明 ,棉铃虫对其主要寄主植物中的次生物质棉酚和烟碱具有很好的适应能力。与此同时 ,棉铃虫中肠微粒体P 4 50酶系的蛋白组成和酶活性发生了不同的变化 ,有升有降 ,有的没有变化。棉铃虫可能通过调整P 4 50酶系的各种蛋白含量和酶的活力水平 ,来适应对植物次生物质的代谢解毒的需要。另外 ,棉铃虫取食棉酚和烟碱后 ,细胞色素B5含量均显著提高 ,而细胞色素P 4 50含量均显著降低 ,细胞色素B5在棉铃虫对棉酚和烟碱的解毒代谢中可能发挥着更为重要的作用     

Induction of P450 monooxygenases in the German cockroach,Blattella germanica L

The cytochrome P450 monooxygenases are an important metabolic system whose level of activity can be influenced by several dietary constituents. We examined the effects of six known P450 inducers on the levels of total cytochromes P450, cytochrome b(5), and six monooxygenase activities in adult German cockroaches. In addition, the levels of CYP6L1 and CYP9E2 mRNA were also investigated. Phenobarbital treatment resulted in increases in total cytochromes P450 and metabolism of three resorufin analogues, but not CYP6L1 nor CYP9E2 mRNA. There was no significant effect of the other five inducers on any of the monooxygenase parameters we measured. In comparison with other insects, the German cockroach seems unusually refractory to most inducing agents.     

Hydrogen peroxide-mediated inactivation of microsomal cytochrome P450 during monooxygenase reactions

Cytochrome P450 can undergo inactivation following monooxygenase reactions in liver microsomes of untreated, phenobarbital and 3-methylcholanthrene-treated rats and rabbits. The acceleration of cytochrome P450 loss in the presence of catalase inhibitors (sodium azide, hydroxylamine) indicates that hydrogen peroxide is involved in hemoprotein degradation. It was revealed that cytochrome P450 is inactivated mainly by H₂O₂ formed through peroxy complex breakdown, whereas H₂O₂ formed via the dismutation of superoxide anions produces a slight inactivating effect. The hydrogen peroxide added outside or formed by a glucose-glucose oxidase system has less of an inactivating effect than H₂O₂ produced within the cytochrome P450 active center. Self-inactivation of cytochrome P450 during oxygenase reactions is highly specific. Other components of the monooxygenase system, such as cytochrome b₅, NADH- and NADPH-specific flavorproteins, undergo no inactivation. The alterations in phospholipid content and in the rate of lipid peroxidation were not observed as well. The inactivation of cytochrome P450 by H₂O₂ is the result of heme loss or destruction without cytochrome P420 formation. Such. a mechanism operates with different substrates and cytochrome P450 species catalyzing the partially coupled monooxygenase reactions.     

细胞色素P450介导抗性的进化可塑性

细胞色素P450是超基因家族,由其介导的杀虫剂代谢解毒的增强是昆虫产生抗药性的普遍而主要的机制。近年的研究表明,细胞色素P450介导的代谢抗性表现出一定程度的进化可塑性:即使是同种昆虫的不同种群在相同种类杀虫剂的胁迫下,进化选择出的抗性相关的细胞色素P450也有所不同,抗性的产生也可以是几种不同细胞色素P450协同作用或控制P450表达的调控因子的不同。     

Cloning and characterization of the NADPH cytochrome P450 reductase gene (CPR) from Candida bombicola

Candida bombicola is a yeast with at least two appealing features. The species can grow on alkanes when provided as the sole carbon source, and it produces glycolipids, which have several industrial, cosmetic and pharmaceutical applications. Both metabolic processes require in their pathway the activity of cytochrome P450 monooxygenase. This enzyme needs and gets reducing equivalents from NADPH cytochrome P450 reductase (CPR). The CPR gene of Candida bombicola was isolated using degenerate PCR and genomic walking. The gene encodes an enzyme of 687 amino acids, which shows homology with known CPRs of other species. The functionality of the gene was proven by heterologous expression in Escherichia coli. The recombinant protein exhibited NADPH-dependent cytochrome c reducing activity. Cloning and characterization of this enzyme is an important step in the study of the cytochrome P450 monooxygenase system of Candida bombicola. The GenBank accession number of the sequence described in this article is EF050789.     

Mechanism of inhibiting the cytochrome P-450-dependent monooxygenase system in liver with fluorocarbons]

The inducer of the liver monooxygenase system perfluorodecalin added to microsomes as a submicron emulsion forms an enzyme-substrate complex with cytochrome P-450. The K(app) values for the perfluorodecalin binding to cytochrome P-450 in microsomes isolated from the livers of control and phenobarbital-treated rats are 5 x 10(-5) M and 2.3 x 10(-6) M, respectively. Perfluorodecalin competitively inhibits the binding of substrates to cytochrome P-450 and decreases the rates of monooxygenase reactions. Perfluorodecalin extrusion from the active center of cytochrome P-450 occurs when an excess of perfluorocarbons non-interacting with cytochrome P-450 is added to microsomes. There is a significant vagueness in the rates of various monooxygenase reactions because of simultaneous induction and inhibition of monooxygenase enzymes after perfluorodecalin administration to rats. The data obtained are consistent with the hypothesis that constitutive forms of cytochrome P-450 are primary receptors for xenobiotic-inducers of phenobarbital-type cytochrome P-450 isoforms.     

Regio- and stereoselective regulation of monooxygenase activities by isoenzyme-selective phosphorylation of cytochrome P450

The phosphorylation of the two major phenobarbital-inducible cytochrome P450 isoenzymes IIB1 and IIB2 was increased in hepatocytes by the action of the membrane permeating cAMP derivatives N6-dibutyryl-cAMP and 8-thiomethyl-cAMP. Under these conditions the dealkylation of 7-pentoxyresorufin, a selective substrate of cytochrome P450IIB1 and P450IIB2 was markedly reduced. 16 beta-Hydroxylation of testosterone which is catalyzed specifically only by cytochrome P450IIB1 and IIB2 was strongly reduced; for 16 alpha-hydroxylation which is also catalyzed by cytochrome P450IIB1 and IIB2 but additionally by 3 further cytochrome P450 isoenzymes, this reduction was less pronounced; for the oxidation of the 17 beta-hydroxyl group which besides cytochromes P450IIB1 and IIB2 is additionally catalyzed not only by other cytochromes P450 but also by 17 beta-hydroxysteroid dehydrogenase there was a clear tendency of reduction which, however, no longer reached statistical significance. Hydroxylation at other positions of testosterone which are catalyzed by other cytochrome P450 isoenzymes were not significantly changed. Hence isoenzyme-selective phosphorylation of cytochrome P450 leads to a corresponding isoenzyme-selective modulation of monooxygenase activity which holds promise to be especially important as a fast regulation of the control of genotoxic metabolites.     

Transcriptional regulation of the grape cytochrome P450 monooxygenase gene CYP736B expression in response to <Emphasis Type="Italic">Xylella fastidiosa</Emphasis> infection

Background  

Plant cytochrome P450 monooxygenases (CYP) mediate synthesis and metabolism of many physiologically important primary and secondary compounds that are related to plant defense against a range of pathogenic microbes and insects. To determine if cytochrome P450 monooxygenases are involved in defense response to Xylella fastidiosa (Xf) infection, we investigated expression and regulatory mechanisms of the cytochrome P450 monooxygenase CYP736B gene in both disease resistant and susceptible grapevines.     

Test systems for biomonitoring based on membrane-bound enzyme complexes. V. Mixed-function monooxygenase induction in the liver microsomes of Lake Baikal fish

The content of cytochrome P450 and monooxygenase activity has been studied in the liver of Baikal fishes (Coregonus automnalis, Thymallus articus, Brachymystax lenok and Cottocomphorus greminsky). The administration of 3-methylcholanthrene increases considerably the level of metabolic activity of microsomal fraction and cytochrome P450 content in liver. The data of microsomal fractions of rats and fishes liver electrophoresis have shown that xenobiotic causes the synthesis of similar according to the molecular weight forms of cytochrome P450 in these animals. The induction of microsomal monooxygenase inhibits the lipid peroxidation of microsomal fraction.