野生型犬尿氨酸酶表达载体的构建及酶活性检测

目的构建野生型犬尿氨酸酶(KYNU)的真核表达载体,并分析其在HEK293细胞中的表达及其酶活性。方法抽提人肝脏细胞的总RNA,通过反转录聚合酶链反应(RT-PCR)法获得KYNU基因全长cDNA,将野生型KYNU基因克隆到pcDNA载体质粒中,获得野生型pcDNA-KYNU重组表达质粒,经酶切鉴定和测序验证后转染HEK293细胞,用蛋白质印迹法技术检测野生型KYNU在细胞中的表达,用高效液相色谱法(HPLC)检测HEK293细胞表达的野生型KYNU酶蛋白的活性。结果通过测序及酶切鉴定野生型pcDNAKYNU重组表达质粒扩增后的PCR产物电泳结果显示构建成功,蛋白质印迹法结果显示转染有重组野生型cDNA-KYNU质粒的HEK293细胞能表达KYNU蛋白,HPLC结果显示野生型KYNU酶存在活性。结论成功构建野生型pcDNA-KYNU的真核表达载体,野生型重组质粒在HEK293细胞中能够表达KYNU并具有一定的酶活性。     

核酸疫苗pVAX1-F的构建及瞬时表达

目的:构建仙台病毒核酸疫苗pVAXl-F,并在COS 7细胞中表达.方法:利用PCR法以仙台病毒cDNA为模板扩增出F基因,与pMD18-T连接,测序正确后用HindⅢ/EcoR Ⅰ双酶切,将F基因引入经同样酶切的pVAX1载体,构建pVAX1-F表达载体,用PCR法和双酶切法鉴定,并将此重组质粒通过脂质体介导转染COS 7细胞,流式细胞术检测抗原蛋白表达、RT-PCR法检测外源基因的表达.结果:经PCR法和酶切鉴定,目的片段大小与预期相符,经测序目的基因序列与GenBank(EF679198)公布结果一致.重组质粒pVAX1-F转染COS 7细胞72 h后,能够表达抗原蛋白,流式细胞术检测达到58.3%,与对照组3.6%比较差异具有显著性(P<0.01),且F基因mRNA明显表达.结论:成功构建pVAX1-F,并能够在COS 7细胞中瞬时表达,为仙台病毒F基因核酸疫苗进行免疫学评价奠定基础.     

人 G类有机磷毒剂水解酶的性质(英文)

观察了部分纯化的人肝 G类毒剂水解酶 ( G酶 )的一些生化性质 .二硫苏糖醇 ( 5mmol·L-1)使G酶活性在 37℃ ,30 min内抑制 35% ;对氯汞苯甲酸 ( 1 - 1 0 0 0 μmol· L-1)不影响 G酶活性 .说明二硫键对酶分子的三维结构至关重要 ,而没有游离巯基参与酶的催化反应 .人肝 G酶专一性地水解带P- F键的有机磷化合物梭曼 ,但不催化带 P- O,P- C或 P- S键的有机磷化合物的反应 .     

基于STAT3转录调节的筛药模型的建立

目的　依据造血生长因子信号转导途径中重要转录因子STAT3的转录调节作用建立基于报告基因的靶向STAT3转录调节的筛药模型 ,用此模型筛选具有G CSF样活性的化合物。方法　构建诱导性表达载体 pTKS3 CAT并转染入表达G CSF受体的NFS 6 0不依赖细胞 ,筛选报告基因CAT表达受rhG CSF诱导的阳性克隆 ,采用ELISA法检测化合物对CAT表达活性的影响。同时 ,对模型的特异性和灵敏性进行检测。结果　在转染有重组质粒的NFS 6 0不依赖细胞中 ,CAT表达受rhG CSF诱导并呈剂量依赖关系 ,EC50 等于 0 0 44nmol·L-1,而rhEPO不能诱导CAT表达。结论　以上模型的CAT基因表达活性能够被其特异性配体强诱导表达 ,利用此模型在 96孔板上用ELISA法测定CAT基因的诱导表达水平可筛选具有G CSF样活性的化合物。     

SARI基因真核表达载体的构建及稳定转染HeLa细胞系的建立

目的构建人SARI基因真核表达载体,并建立稳定转染的HeLa细胞系。方法采用RT-PCR技术从正常人外周血单个核细胞cDNA文库中扩增SARI基因序列,连接插入至pCMV-N-Flag真核表达载体,并对重组质粒进行酶切及测序鉴定;阳离子聚合物介导重组质粒转染HeLa细胞后,用G418抗生素筛选稳定转染的细胞系。间接免疫荧光检测Flag-SARI融合蛋白在HeLa细胞系中的表达定位。RT-PCR及Western blot检测SARI mRNA及蛋白的表达变化。结果双酶切和DNA测序表明pCMV-Flag-SARI真核表达质粒构建成功。经G418筛选后,RT-PCR和Western blot表明,转染重组质粒的HeLa细胞系中SARI mRNA及蛋白的表达明显升高。间接免疫荧光结果显示,Flag-SARI融合蛋白在HeLa细胞系的胞质和胞核中均有表达,且胞质荧光信号强于胞核。结论成功构建pCMV-Flag-SARI真核表达载体,表达的FlagSARI蛋白主要定位于HeLa细胞系的胞质中。     

人白细胞介素24真核表达载体的构建及其在HepG2细胞中的表达

目的 构建人白细胞介素24(human interleukin-24,hIL-24)真核表达载体,并在HepG2细胞中稳定表达,为进一步研究其抗肿瘤作用奠定基础.方法 采用逆转录聚合酶链反应(RT-PCR),从植物血凝素活化的人外周血单个核细胞中克隆得到hIL-24基因目的 片段.应用DNA重组技术将IL-24PCR产物双酶切后定向克隆至真核表达载体pcDNA3.1(+),转化大肠杆菌DHSα获得重组载体,进行PCR、酶切及测序鉴定.应用脂质体将鉴定正确的重组质粒转染至HepG2细胞,用G418筛选稳定转染细胞株.采用RT-PCR检测稳定转染细胞HepG2中IL-24 mRNA的表达.结果 通过RT-PCR获得与预期大小一致约600 bp的IL-24基因片段;重组载体pcDNA3.1(+)-IL-24经PCR、双酶切及测序证实,IL-24 eDNA片段已正确插入真核表达载体中;在稳定转染的HepG2细胞株中可见到IL-24 mRNA表达.结论 成功构建了hIL-24真核表达载体pcDNA3.1(+)-IL-24,并获得了稳定转染该重组质粒的HepG2细胞株.     

抑制IGF2基因的siRNA表达载体对肝癌Huh-7细胞增殖的抑制作用

目的:研究抑制人胰岛素样生长因子2(IGF2)基因的siRNA表达载体对肝癌Huh-7细胞增殖的抑制作用。方法:将重组人甲胎蛋白(hAFP)和人端粒酶逆转录酶(hTERT)双启动子调控抑制IGF2基因的siRNA表达载体pGL3-h AFP-hTERT-siRNA3(简称siRNA3)转染Huh-7细胞和正常肝L-02细胞,另设阴性对照(载体p GL3-hAFP-hTERT)组和空白对照组。采用实时荧光定量聚合酶链反应法检测各组细胞转染48 h后IGF2 mRNA表达;酶标仪检测转染0、24、48、72 h后的细胞活性;流式细胞仪检测转染48h后细胞周期、细胞凋亡;Western blot法检测细胞IGF2、增殖细胞核抗原(PCNA)、细胞周期蛋白(Cyclin)E2、Cyclin D2、Cdc2、Bcl-2蛋白表达水平。结果:与阴性对照组和空白对照组比较,转染siRNA3的Huh-7细胞中IGF2 mRNA表达明显减弱,转染48、72 h后Huh-7细胞活性明显降低,G1期Huh-7细胞明显增加,S期Huh-7细胞明显减少;Huh-7细胞早期、晚期及总凋亡百分比均明显增加,IGF2、PCNA、Cyclin E2、Cyclin D2、Cdc2和Bcl-2蛋白表达均明显减弱,以上差异具有统计学意义(P<0.01或P<0.05)。转染siRNA3表达载体的L-02细胞上述指标均无明显变化(P>0.05)。结论:重组hAFP和hTERT双启动子调控针对IGF2基因的siRNA可特异性抑制Huh-7细胞IGF2表达及细胞增殖,其可能与下调IGF2 mRNA及蛋白表达,进而引起细胞增殖相关基因PCNA、细胞周期调控相关基因Cyclin E2、Cyclin D2、Cdc2及细胞凋亡调控相关基因Bcl-2蛋白表达下调有关。     

稳定整合靶向EGFL7基因的shRNA载体的胶质瘤细胞系的建立

目的构建针对EGFL7基因的特异性RNA干扰载体,建立稳定转染该干扰载体的人胶质瘤细胞系。方法根据EGFL7基因的编码序列设计并合成针对EGFL7基因的特异性shRNA,将其克隆入pSilencer3.1-H1neo载体中,重组载体经脂质体LipofectamineTM2000介导转染胶质瘤细胞株U251;转染细胞经G418筛选,采用Westernblot方法在蛋白水平检测筛选出的G418抗性的克隆细胞。结果酶切鉴定和测序证实,成功构建了靶向EGFL7基因的shRNA真核表达载体pSilencer-shEGFL7,并获得了稳定表达靶向EGFL7基因的shRNA的胶质瘤细胞株。结论 EGFL7基因特异性RNA干扰载体能够显著抑制EGFL7基因在U251细胞中的表达,这为进一步研究EGFL7在胶质瘤细胞系U251中的生物学功能和作用机制奠定了基础。     

携带人PPARα基因高效真核表达载体的构建及其意义

目的构建可以高效表达人过氧化物酶体增殖物激活受体(αhPPARα)的真核细胞表达载体,为筛选作用于PPARα受体的药物提供分子平台。方法将HepG2细胞总RNA经逆转录-聚合酶链式反应(RT-PCR)克隆hPPARα全长基因,用BamHⅠ、SalⅠ双酶切后,与相同双酶切的pIRES2-EGFP载体连接,构建phPPARα-IRES2-EGFP重组质粒,用酶切及基因测序鉴定重组质粒中hPPARα基因的完整性和可靠性;重组质粒转染293细胞,荧光显微镜观察EGFP报告基因表达强度,并对转染细胞的hPPARα表达进行荧光定量PCR及免疫细胞化学检测。结果经酶切和测序证实重组质粒构建正确,并在转染的293细胞中获得hPPARα的高效表达。结论成功构建重组质粒phPPARα-IRES2-EG-FP,为基于hPPARα受体靶点的药物筛选平台的建立提供了高效表达hPPARα的重组载体。     

转染bFGF基因对人骨髓间充质干细胞增殖特性的影响

目的 探讨作为组织工程种子细胞的人骨髓间充质干细胞,在体外培养条件下转染bFGF基因对其增殖特性的影响.方法 利用脂质体将含人pcDNA3.1-bFGF质粒转染到生长良好的P3代人BMSCs,G418筛选获得抗性克隆.采用荧光定量PCR和免疫荧光检测转染bFGF的骨髓间充质干细胞bFGF基因及其产物的表达,MTY法检测和流式细胞仪检测细胞的增殖情况和细胞增殖周期,并将转染和非转染BMSCs分别成骨诱导分化,对其碱性磷酸酶活性进行测定.结果 脂质体介导pcDNA3.1-bFGF重组表达质粒转染BMSCs,经荧光定量PCR和免疫荧光检测.证实转染细胞表达bFGF.转染细胞增殖活力加强,处于增殖周期的细胞比例更高（P〈0.05）.碱性磷酸酶活性检测结果表明转染细胞的碱性磷酸酶活性高于非转染细胞（P〈0.05）.结论 用脂质体转染法能将pcDNA3.1-bFGF成功导入体外培养的hBMSCs,bFGF基因改良的BMSCs可以改善其生存状态、促进其增殖,并可促进向成骨细胞分化.     

Production of human liver prolidase by Saccharomyces cerevisiae as host cells

INTRODUCTION Mazur[1]first described the hydrolysis and detoxi-fication of diisopropylfluorophosphate (DFP) usingcrude preparations from human and rabbit tissues in1946. Organophosphoric acid anhydrolases (OPAA,EC 3.1.8.2) have been found in a wide variety ofprokaryotes and eukaryotes such as bacteria, protozoa,Altermonas haloplanktis[7] showed prolidase activity, Isolation of prolidase gene The human liversuggesting that the OPAA may be a prolidase[8]. These …     

Dual activities of human prolidase.

The cDNA encoding human liver prolidase derived from a healthy adult's liver was cloned into the expression vector pPIC9K of Pichia pastoris to construct the recombination expression vector pPIC9K-P. The pPIC9K-P was digested by restriction enzyme Pme I, and then transformed into P. pastoris GS115 by electroporation. Transformants (the insertion recombinant) were induced by methanol to express the recombination protein. The optimal induction conditions (medium pH, methanol concentration and induction time) of the insertion transformant with the highest enzymatic activity were estimated by orthogonal experimental design L9(3(4)). The SDS-PAGE of the recombinant human prolidase (rh-prolidase) in induction medium showed a molecular weight of 73 kDa. The activities of the rh-prolidase and organophosphoric acid anhydrolases (OPAA) were assayed by colorimetric methods. The recombinant enzyme catalyzed the hydrolysis of organophosphorous compound soman as well as the hydrolysis of dipeptide Gly-Pro. Under the optimal induction conditions, the maximal activities of prolidase and OPAA came to 44.1 and 54.8 nmol/min/mg protein respectively in the medium supernatant. The rh-prolidase purified from the supernatant by ion exchange gradient chromatography (DEAE-Sepharose Fast Flow) and gel filtration chromatography (Sephacryl S-200 High Resolution) showed a single band by SDS-PAGE analysis. The purified rh-prolidase could decompose soman via hydrolytic reaction in vitro.     

In vitro characterization of organophosphorus compound hydrolysis by native and recombinant human prolidase.

Human prolidase is a binuclear metalloenzyme, which can potentially function as a catalytic bioscavenger for organophosphorus (OP) nerve agents. Although the biochemical properties of native prolidase purified from human erythrocytes, liver, kidney, and fibroblast cells are well known, it is very poorly characterized with regard to its OP hydrolyzing activity. Also, the high cost of purification of large quantities of native enzyme limits its use as a bioscavenger. Thus, recombinant human prolidase with similar biochemical properties to those of native enzyme would be more suitable as a catalytic bioscavenger. In this study, we established an Escherichia coli expression system, which produced a large amount of tagged human liver prolidase that was purified to over 95% purity from the soluble fraction of cell lysate by affinity chromatography on Streptavidin-agarose resin. The catalytic properties of the recombinant enzyme were compared in vitro with those of highly purified prolidase I isolated from human erythrocytes. The catalytic properties of recombinant prolidase overlap with those of the erythrocyte-derived native enzyme. Both enzymes efficiently hydrolyzed diisopropylfluorophosphate, sarin, soman, tabun and cyclosarin, but were much less efficient at hydrolyzing paraoxon and methyl paraoxon. These results suggest that human prolidase expressed in E. coli is suitable for further development as a catalytic bioscavenger for OP nerve agents.     

Prolidase, a potential enzyme target for melanoma: design of proline-containing dipeptide-like prodrugs

Bioinformatics tools such as Perl, Visual Basic, Cluster, and TreeView were used to analyze public gene expression databases in order to identify potential enzyme targets for prodrug strategies. The analyses indicated that prolidase might be a desirable enzyme target based on its differential expression in melanoma cancer cell lines and its high substrate specificity for dipeptides containing proline at the carboxy terminus. RT-PCR expression of prolidase and hydrolytic activity against N-glycyl-l-proline (GLY-PRO), a standard substrate of prolidase, determined in tumor cell lines, exhibited a high correlation (r(2) = 0.95). These results suggest the possibility of targeting prolidase with prodrugs of anticancer agents for enhanced selectivity. The feasibility of such a scenario was tested by (a) synthesizing prodrugs of melphalan that comprised linkage of the carboxy terminus of the l-phenylalanine moiety of melphalan to the N-terminus of l and d stereoisomers of proline and (b) determining their bioconversion and antiproliferative activities in SK-MEL-5 cells, a melanoma cancer cell line with high expression levels of prolidase. The results of hydrolysis studies of the l- and d-proline prodrugs of melphalan, designated as prophalan-l and prophalan-d, respectively, indicated a approximately 7-fold higher rate of activation of prophalan-l compared to prophalan-d in SK-MEL-5 cell homogenates. Prophalan-l exhibited cytotoxicity (GI(50) = 74.8 microM) comparable to that of melphalan (GI(50) = 57.0 microM) in SK-MEL-5 cells while prophalan-d was ineffective, suggesting that prolidase-specific activation to the parent drug may be essential for cytotoxic action. Thus, melphalan prodrugs such as prophalan-l that are cleavable by prolidase offer the potential for enhanced selectivity by facilitating cytotoxic activity only in cells overexpressing prolidase.     

An in vitro and in vivo evaluation of the efficacy of recombinant human liver prolidase as a catalytic bioscavenger of chemical warfare nerve agents

In this study, we determined the ability of recombinant human liver prolidase to hydrolyze nerve agents in vitro and its ability to afford protection in vivo in mice. Using adenovirus containing the human liver prolidase gene, the enzyme was over expressed by 200- to 300-fold in mouse liver and purified to homogeneity by affinity and gel filtration chromatography. The purified enzyme hydrolyzed sarin, cyclosarin and soman with varying rates of hydrolysis. The most efficient hydrolysis was with sarin, followed by soman and by cyclosarin {apparent k_cat/K_m [(1.9?±?0.3), (1.7?±?0.2), and (0.45?±?0.04)]?×?10^5?M^?1?min^?1, respectively}; VX and tabun were not hydrolyzed by the recombinant enzyme. The enzyme hydrolyzed P (+) isomers faster than the P (?) isomers. The ability of recombinant human liver prolidase to afford 24 hour survival against a cumulative dose of 2?×?LD₅₀ of each nerve agent was investigated in mice. Compared to mice injected with a control virus, mice injected with the prolidase expressing virus contained (29?±?7)-fold higher levels of the enzyme in their blood on day 5. Challenging these mice with two consecutive 1?×?LD₅₀ doses of sarin, cyclosarin, and soman resulted in the death of all animals within 5 to 8?min from nerve agent toxicity. In contrast, mice injected with the adenovirus expressing mouse butyrylcholinesterase, an enzyme which is known to afford protection in vivo, survived multiple 1?×?LD₅₀ challenges of these nerve agents and displayed no signs of toxicity. These results suggest that, while prolidase can hydrolyze certain G-type nerve agents in vitro, the enzyme does not offer 24 hour protection against a cumulative dose of 2?×?LD₅₀ of G-agents in mice in vivo.     

Utilization of peptide carrier system to improve intestinal absorption: targeting prolidase as a prodrug-converting enzyme.

The feasibility of targeting prolidase as a peptide prodrug-converting enzyme has been examined. The enzymatic hydrolysis by prolidase of substrates for the peptide transporter L-alpha-methyldopa-pro and several dipeptide analogues without an N-terminal alpha-amino group (phenylpropionylproline, phenylacetylproline, N-benzoylproline, and N-acetylproline) was investigated. The Michaelis-Menten parameters Km and Vmax for L-alpha-methyldopa-pro are 0.09 +/- 0.02 mM and 3.98 +/- 0.25 mumol/min/mg protein, respectively. However, no hydrolysis of the dipeptide analogues without an N-terminal alpha-amino group is observed, suggesting that an N-terminal alpha-amino group is required for prolidase activity. These results demonstrate that prolidase may serve as a prodrug-converting enzyme for the dipeptide-type prodrugs, utilizing the peptide carrier for transport of prodrugs into the mucosal cells and prolidase, a cytosolic enzyme, to release the drug. However, a free alpha-amino group appears to be necessary for prolidase hydrolysis.     

Peptide Transporter Function and Prolidase Activities in Caco-2 Cells: A Lack of Coordinated Expression

Abstract

Peptide transport and prolidase activities were measured to determine whether the expression of these two components of protein nutrition are coordinately regulated; i.e., whether an increase in the peptide transporter function will necessarily lead to a higher prolidase activity, or vice versa. The results indicated that peptide transporter function and prolidase activity respond differently to cell differentiation and feeding schedules. The results also indicated that peptide transport and prolidase activities were different in two Caco-2 cell “clones”, with S-K cells transported peptides at higher rates but had lower total prolidase activities, when compared to ATCC cells. These results suggest that the expression of the peptide transporter function and prolidase activity is not coordinated. In addition, both the transporter and the prolidase activities affected the overall transport of Phe when given as the dipeptide Phe-Pro, supporting the notion that intestinal absorption of peptides is an essential component of amino acid absorption. In conclusion, the evidence suggests that the peptide transporter function and prolidase activity are not coordinately expressed by the human intestinal Caco-2 cells.     

Species differences in tissue distribution and enzyme activities of arylacetamide deacetylase in human, rat, and mouse

Human arylacetamide deacetylase (AADAC) is a major esterase responsible for the hydrolysis of clinical drugs such as flutamide, phenacetin, and rifampicin. Thus, AADAC is considered to be a relevant enzyme in preclinical drug development, but there is little information about species differences with AADAC. This study investigated the species differences in the tissue distribution and enzyme activities of AADAC. In human, AADAC mRNA was highly expressed in liver and the gastrointestinal tract, followed by bladder. In rat and mouse, AADAC mRNA was expressed in liver at the highest level, followed by the gastrointestinal tract and kidney. The expression levels in rat tissues were approximately 7- and 10-fold lower than those in human and mouse tissues, respectively. To compare the catalytic efficiency of AADAC among three species, each recombinant AADAC was constructed, and enzyme activities were evaluated by normalizing with the expression levels of AADAC. Flutamide and phenacetin hydrolase activities were detected by the recombinant AADAC of all species. In flutamide hydrolysis, liver microsomes of all species showed similar catalytic efficiencies, despite the lower AADAC mRNA expression in rat liver. In phenacetin hydrolysis, rat liver microsomes showed approximately 4- to 6.5-fold lower activity than human and mouse liver microsomes. High rifampicin hydrolase activity was detected only by recombinant human AADAC and human liver and jejunum microsomes. Taken together, the results of this study clarified the species differences in the tissue distribution and enzyme activities of AADAC and facilitate our understanding of species differences in drug hydrolysis.     

Purification and characterization of recombinant human liver prolidase expressed in Saccharomyces cerevisiae

The recombinant human liver prolidase (rh-prolidase, EC 3.4.13.9) from the lysate supernatant of engineering yeast Saccharomyces cerevisiae was purified in two steps employing anion-exchange gradient chromatography (DEAE-Sepharose fast flow) and gel filtration chromatography (Sephacryl S-200 high resolution). The purified recombinant protein furnished a single band with a molecular weight of 56 kD. Intensity scanning of the SDS-PAGE gel revealed that the prolidase accounted for more than 90% of total protein. The optimum pH of the catalytic reaction was 8.0. The enzyme was stimulated by Mn²⁺, but strongly inhibited by Cu²⁺ and Zn²⁺. The rh-prolidase expressed in S. cerevisiae had both dipeptidase and organophosphorus acid anhydrolase activity. It catalyzed the hydrolysis of soman and the dipeptide Gly–Pro. In a detoxification test in vitro, purified rh-prolidase was remarkably efficient at eliminating the toxicity of a lethal dose of soman, with the result that mice survived injection of such a dose.