人肝谷胱甘肽转移酶的纯化和性质

谷胱甘肽转移酶(EC 2,5,1,18 Glutathione S-transferases简称GSTs)是一组具有多种生理功能的蛋白质。我们通过105,000×g超速离心,s—已基—谷胱甘肽—Sepharose-6B亲和层析柱和DEAE52纤维柱或CM52纤维柱将人肝粗匀浆纯化为电泳纯的GSTs同工酶。经系和层析柱后GSTs比活比粗匀浆上清液提高54倍,回收率近60％。通过DE52柱将人肝GSTs分离为7个同工酶组分,分别称为c_(DE),A_1,A_2,A_3,A_4,A_5和A_6,经等电聚焦电泳和SDS-pAGE电泳鉴定,其等电点依次为8.60,7.05,6.70,6:60,6.55,6.45和6.4。经CM52柱后得到5个不同的同工酶组分,分别定名为A_(CM),c_1,c_2,c_3和c_4等电点各自为 6.30,7.00,8.50,8.55和8.60。阳离子同工酶(即c_(DE),C_1,C_2,C_3和C_4)的分子量在23,500—24,000道尔顿,阴离子同工酶(A_(CM),A_1-A_6)约为25,000道尔顿。并将亲和层析柱后样品,阳离子同工酶C_(DE)和阴离子同工酶A_(CM)作为抗原,得到兔抗人肝GSTs相应同工酶的抗血清,其抗血清效价经免疫双扩散法测定分别为1:96,1:64,1:16。并对人肝GSTs进行氨基酸组份的测定。     

肠出血性大肠杆菌(EHEC)O157∶H7紧密粘附素免疫保护性片段(Intimin-C)的克隆表达纯化及部分生物学活性研究

克隆表达并纯化肠出血性大肠杆菌 (EHEC)O15 7∶H7紧密粘附素免疫保护性片段 (Intimin C) ,并对其部分生物学活性进行研究。设计引物采用PCR自O15 7菌基因组扩增紧密粘附素免疫保护性片段 (Intimin C)的编码基因eae C ,T A克隆测序后构建原核表达质粒 pET 2 8a(+) eaeC并转化E .coliBL2 1(DE3) ,诱导表达破菌及包涵体洗涤后采用离子交换柱和亲和层析柱对目的蛋白进行纯化 ,PAGE电泳初测目的蛋白的分子量、滴定法初测目的蛋白的等电点 ,并以纯化蛋白Intimin C免疫家兔制备多抗血清。采用PCR法自O15 7菌基因组扩增出了约 90 0b…     

离子交换层析初步分离大鼠肝蛋白水解酶、ADAMs、ACP、AKP和PCNA

用DEAE 离子交换层析法分离 2 /3肝切除 ( partialhepatectomy ,PH)后恢复 4、 3 6和 14 4h的大鼠再生肝及正常肝的蛋白水解酶、ADAMs、ACP、AKP和PCNA ;用SDS PAGE、Western blot、酶复性电泳等方法 ,分析了它们在不同洗脱段中的分布及活性变化 ,为分离与肝再生有关的蛋白 (酶 )提供了资料。     

铝对肝、肾、心、脑所致损害的实验研究

240只Wistar大鼠,体重(150～300g)分为四组,A组(正常对照)60只、B组(柠檬酸组)60只每天给AlCl_3与柠檬酸盐混合饲料(按1:11)、C组和D组各60只,每天被摄入含500ppm/kg、2500ppm/kg的Alcl_3混合饲料,分别在3个月、6个月、12个月后处死,然后观察铝对其肝、肾、心肌、脑影响的组织化学及超微结构等变化。组织化学结果显示:上述器官的SDH、Mg~(2+)—ATPase、ChE、G-6-Pase的活性及糖原(PAS反应)C组及D组明显低于A组。而LDH及ACP活性较A组高(P<0.01)。超微结构变化为C组与D组的肝、肾、心肌、脑细胞内线粒体及内质网受损,大鼠神经细胞变性,而且突触囊泡聚积在突触前膜;A组(正常组)没有上述变化。同时铝沉积于脉络丛和神经细胞内。综上所述,铝可造成肝、肾、心肌、脑细胞的功能和结构的损害。     

二乙基亚硝胺诱发大鼠肝脏癌变过程中醛缩酶同功酶基因表达的改变

二乙基亚硝胺诱发大鼠肝脏癌变时,伴随血清AFP浓度的升高,肝脏组织内醛缩酶活力和醛缩酶同功酶谱发生改变。在诱癌的前8周中,以FIP为底物的醛缩酶活力迅速下降,8周以后保持着较低的活力水平,而以FDP为底物的醛缩酶活力在前16周中变化不显著,在16周后迅速增高。所以对两个底物的活力比,正常成年大鼠肝脏是1.03,原发性肝癌是4.53,移植性肝癌BERH-2第71代是7.52。醋酸纤维薄膜电泳显示正常成年肝脏有醛缩酶B_4,B_3A_1区带,诱癌后B型醛缩酶区带减弱,诱癌4周出现醛缩酶A_4区带,诱癌12周出现A_1C_3区带,部分原发性肝癌中还出现醛缩酶C_4区带。实验结果说明肝癌发生过程中,醛缩酶B基因逐渐受到“封闭”,醛缩酶A基因和醛缩酶C基因依次逐渐“开放”。     

大鼠肝癌和正常肝染色质非组蛋白(HAP_2)的双向凝胶电泳比较~*

利用等电点聚焦(IEF)和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)的双向电泳以及高度灵敏的银染色相结合的方法,对大鼠肝癌和正常肝染色质非组蛋白进行了对比分析。结果指出,在两个样品中均可看到五百个左右的蛋白点。关于这些蛋白点的分布,正常肝在较大分子量和较高等电点区域有较高的相对百分率,而肝癌在较低分子量和较低等电点区域有较高的相对百分率。与正常肝制品比较,肝癌制品中出现了一些独有的蛋白质点子,而在正常肝中原有的一些点子却消失了。     

大鼠肝tRNA~(Ⅱe)基因在大肠杆菌中的表达及分离纯化

利用T7RNA聚合酶／启动子表达系统在大肠杆菌JM109（DE3）中表达化学合成的大鼠肝tRNAⅡe基因．经酚抽提、DEAE-52离子交换柱层析及HPLC层析,分离纯化大鼠肝tRNAⅡe．变性聚丙烯酰胺凝胶电泳和Northern-blot鉴定表明,大鼠肝tRNAⅡe基因成功地获得表达．氨酸化活性检测表明：纯化后,每1A260单位（40μg）的tRNAⅡe可负载约650pmol的Ⅱe,纯度为54．2％．说明从大肠杆菌中分离纯化出具有一定生物学活性,一定纯度的合成基因表达产物．     

微粒体细胞色素P-450、NADPH-细胞色素P-450还原酶的纯化与重组活性

经苯巴比妥钠诱导的雄性大白鼠的肝微粒体纯化的细胞色素P-450同功酶组份,经SDS-PAGE鉴定呈电泳纯,分子量为55kD。部分纯化的NADPH-细胞色素P-450还原酶,含72和77kD两个蛋白质组分。上述细胞色素P-450和NADPH-细胞色素P-450还原酶与卵磷脂制备的脂质体重组后的活性试验表明,对艾氏剂有环氧化作用,对环已烷有羟化作用,对溴氰菊酯的羟化作用微弱。当重组系统中缺少细胞色素P-450组份时,对环已烷不再起作用。同时还研究了纯化的细胞色素P-450的光谱特性。     

高山红景天对肝纤维化大鼠PDGF-BB mRNA表达的影响

目的:观察单方生药高山红景天对实验性肝纤维化大鼠的疗效,探讨其可能的作用机制。方法:将实验动物随机分为正常对照组(A)、模型组(B)、秋水仙碱组(C)、红景天高剂量组(D)、红景天低剂量组(E)。除正常对照组外,其余4组均用四氯化碳诱发肝纤维化。各组于造模第8周末处死动物,分别用放射免疫法检测血清层粘连蛋白(LN)、Ⅲ型前胶原(PCⅢ)、透明质酸(HA)及Ⅳ型胶原(CⅣ);RT-PCR检测肝组织PDGF-BB mRNA的表达。结果:与模型组大鼠比较,经该中药治疗,大鼠血清中LN、PCⅢ、HA、CⅣ水平明显降低(P<0.01);大鼠肝组织内PDGF-BBmRNA表达明显下降(P<0.01);大鼠肝组织病理学检测改善显著。结论:单方生药高山红景天能有效地抑制肝纤维化的发展,其机制可能是通过下调肝组织内PDGF-BB mRNA表达,降低ECM的分泌而达到的。     

藤茶总黄酮对大鼠肝纤维化的防治作用

目的:观察藤茶总黄酮(Tengcha flavonoids,TCF)对大鼠肝纤维化的防治作用。方法:66只雄性SD大鼠被随机分为5组:正常对照组(10只),正常喂养;模型组(14只):采用四氯化碳(CCL4)皮下注射诱导大鼠肝纤维化模型;TCF治疗组分为低、中、高剂量组(每组14只):在造模的同时,每日分别予以TCF25mg/100g、50mg/100g、100mg/100g体重灌胃。于第12周末检测血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、透明质酸(HA)、层粘连蛋白(LN)、Ⅲ型前胶原(PCⅢ)、Ⅳ型胶原(CⅣ)的水平以及肝组织中超氧化物歧化酶(SOD)活性、丙二醛(MDA)的含量变化。结果:与模型组比较,TCF各剂量组血清中ALT、AST、HA、LN、PCⅢ、CⅣ的水平显著下降(P<0.05);SOD活性明显增高,MDA的含量明显降低(P<0.05)。结论:TCF对CCL4实验性肝纤维化大鼠有较好的防治作用,其作用机制可能与抗氧化、抗脂质过氧化有关。     

小鼠肝脏免疫抑制蛋白质(LISP)的分离纯化和鉴定

用硫酸铵分段盐析及DEAE-Sephadex A-50、羟磷灰石和CM纤维素等多种柱层析方法,从正常小鼠肝浸液中分离纯化出一种免疫抑制蛋白质(LISP)。在体外用微量该蛋白质就能强烈抑制小鼠T、B淋巴细胞对促有丝分裂原和同种异型抗原的增生反应。纯化的蛋白质在聚丙烯酰胺凝胶电泳(PACE)和等电聚焦(IEF)鉴定时均显示为一条区带,其等电点(pI)值在7.5—7.8范围。沉降系数利S_(20),w为5.39。Sephadex G-100凝胶层析测得LISP的分子量为78,000道尔顿。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)提示LISP是由二个相同的亚基组成,亚基分子量为38,500道尔顿。LISP是一种既非糖蛋白又非脂蛋白的碱性蛋白质,对它的氨基酸组成也作了分析。     

Purification of a new acidic glutathione S-transferase, GST-Yn1Yn1, with a high leukotriene-C4 synthase activity from rat brain

A new acidic form of glutathione S-transferase (GST, pI 6.2) was purified from rat brain by S-hexylglutathione affinity chromatography followed by chromatofocusing. This form occupied 20-25% of the total activity bound to the affinity column. It had a molecular mass (subunit 26 kDa) similar to that of a major GST form of rat testis (MT or 6-6) on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. However, it differed from the MT in isoelectric point, activity towards 1,2-dichloro-4-nitrobenzene and immunological properties. On two-dimensional gel electrophoresis the brain form gave a spot which was identical in molecular mass, isoelectric point and immunological properties to a less acidic one (Yn1) of two spots (Yn1 and Yn2) of the testis GST-MT. Therefore, the brain acidic form is a homodimer, and named GST-Yn1Yn1. The activity was inhibited by sulfasalazine, an inhibitor of leukotriene-C4 synthase. This form (GST-Yn1Yn1) showed the highest leukotriene-C4 synthase activity, 496 nmol/mg protein in 5 min, among nine cytosolic GST isoenzymes from the rat. The Km values for leukotriene A4 and glutathione were 26 microM and 3.5 mM respectively. A major GST form of rat brain, occupying about 40% of the total activity, was identical with GST-P (7-7) purified from rat liver bearing preneoplastic hyperplastic nodules and localized at astroglias. GST-P also showed the significant leukotriene-C4 synthase activity, 67.2 nmol/mg protein in 5 min, but the Km for leukotriene A4 was 100 microM, fourfold higher than that of GST-Yn1 Yn1. These results suggest that mainly GST-Yn1 Yn1 may be involved in leukotriene-C4 synthesis in rat brain.     

Separation and partial characterization of multiple forms of rat liver alcohol dehydrogenase

Rat liver alcohol dehydrogenase was purified and four isoenzyme forms, demonstrated by starch gel electrophoresis, were separated by O-(carboxymethyl)-cellulose chromatography. Each of the isoenzymes had a distinct isoelectric point. All isoenzymes were active with both ethanol (or acetaldehyde) and steroid substrates, and had similar Michaelis-Menten constants for each of the substrates and coenzymes studied. The three isoenzymes with the lowest migration toward the cathode exhibited the same pH optimum of 10.7 for ethanol oxidation, a greater activity with 5 beta-androstan-3 beta-ol-17-one than with ethanol as a substrate, and an unchanged electrophoretic mobility following storage in the presence of 100 microM dithiothreitol. By contrast the isoenzyme with the highest mobility toward the cathode exhibited a pH optimum of 9.5 for ethanol oxidation, a low steroid/ethanol ratio of activity, and converted to the migrating pattern of the two isoenzymes with intermediate mobility when stored. The similarities between the isoenzymes of rat liver alcohol dehydrogenase differ considerably from differences in substrate specificity exhibited by isoenzymes of horse liver alcohol dehydrogenase.     

Comparative studies on the isoenzymes of glutathione S-transferase of rat brain and other tissues

Six forms of glutathione S-transferase (GST) designated as GST 9.3, GST 7.5, GST 6.6, GST 6.1, GST 5.7 and GST 4.9 have been purified to homogeneity from rat brain. All GST isoenzymes of rat brain are apparent homodimers of one of the three type subunits, Ya, Yb, or Yc. More than 60% of total GST activity of rat brain GST activity is associated with the isoenzymes containing only the Yb type of subunits. In these respects brain GST isoenzymes differ from those of lung and liver. The Ya, Yb, and Yc type subunits of brain GST are immunologically similar to the corresponding subunits of liver and lung GST. The isoelectric points and kinetic properties of the Yb type subunit dimers in brain are strikingly different from those of the Yb type dimers present among liver GST isoenzymes indicating subtle differences between these subunits of brain and liver.     

Differential Expression of Phospholipase C Specific for Inositol Phospholipids at the Cell Surface of Rat Glial Cells and REF52 Rat Embryo Fibroblasts

Abstract: Phosphatidylinositol(PI)-specific phospholipase C activity was detected on the surface of rat astrocytes, rat C6 glioma cells, and rat embryo (REF52) fibroblasts. The cell surface phospholipase C (ecto-PLC) activity was calcium-dependent, did not result from secreted phopholipase C, and was not released from the cell surface by bacterial PI-specific phospholipase C. Agents known to stimulate intracellular PI turnover, including carbachol, L-glutamic acid, acetylcholine, and orthovanadate, did not induce measurable alterations in the activity of the ecto-PLC. The expression of ecto-PLC activity by REF52 fibroblasts was density-dependent: subconfluent cultures of REF52 exhibited low levels of activity (less than 80 pmol of inositol phosphate formed/min/10⁶ cells), whereas in confluent cultures ecto-PLC activity increased to approximately 300 pmol/min/10⁶ cells. In contrast to this behavior and that exhibited by previously reported ecto-PLC-positive cell types, the ecto-PLC activity exhibited by astrocytes (approximately 1,000 pmol/min/10⁶ cells) and by C6 glioma cells (approximately 100 pmol/min/10⁶ cells) was independent of cell culture density up to confluence. The constitutive expression of ecto-PLC activity of astroglial cells may be related to their function as accessory cells in close association with neurons.     

Subcellular distribution and properties of aldehyde dehydrogenase from 2-acetylaminofluorine-induced rat hepatomas

The subcellular distribution and properties of four aldehyde dehydrogenase isoenzymes (I-IV) identified in 2-acetylaminofluorene-induced rat hepatomas and three aldehyde dehydrogenases (I-III) identified in normal rat liver are compared. In normal liver, mitochondria (50%) and microsomal fraction (27%) possess the majority of the aldehyde dehydrogenase, with cytosol possessing little, if any, activity. Isoenzymes I-III can be identified in both fractions and differ from each other on the basis of substrate and coenzyme specificity, substrate K(m), inhibition by disulfiram and anti-(hepatoma aldehyde dehydrogenase) sera, and/or isoelectric point. Hepatomas possess considerable cytosolic aldehyde dehydrogenase (20%), in addition to mitochondrial (23%) and microsomal (35%) activity. Although isoenzymes I-III are present in tumour mitochondrial and microsomal fractions, little isoenzyme I or II is found in cytosol. Of hepatoma cytosolic aldehyde dehydrogenase activity, 50% is a hepatoma-specific isoenzyme (IV), differing in several properties from isoenzymes I-III; the remainder of the tumour cytosolic activity is due to isoenzyme III (48%). The data indicate that the tumour-specific aldehyde dehydrogenase phenotype is explainable by qualitative and quantitative changes involving primarily cytosolic and microsomal aldehyde dehydrogenase. The qualitative change requires the derepression of a gene for an aldehyde dehydrogenase expressed in normal liver only after exposure to potentially harmful xenobiotics. The quantitative change involves both an increase in activity and a change in subcellular location of a basal normal-liver aldehyde dehydrogenase isoenzyme.     

Purification and characterization of alpha-amylase from rat pancreatic acinar carcinoma. Comparison with pancreatic alpha-amylase.

alpha-Amylase was purified to apparent homogeneity from normal pancreas and a transplantable pancreatic acinar carcinoma of the rat by affinity chromatography on alpha-glucohydrolase inhibitor (alpha-GHI) bound to aminohexyl-Sepharose 4B. Recovery was 95-100% for both pancreas and tumour alpha-amylases. They were monomeric proteins, with Mr approx. 54000 on SDS/polyacrylamide-gel electrophoresis. Isoelectric focusing of both normal and tumour alpha-amylases resolved each into two major isoenzymes, with pI 8.3 and 8.7. Tumour-derived alpha-amylase contained two additional minor isoenzymes, with pI 7.6 and 6.95 respectively. All four tumour isoenzymes demonstrated amylolytic activity when isoelectric-focused gels were treated with starch and stained with iodine. Two-dimensional electrophoresis, on SDS/10-20%-polyacrylamide-gradient gels after isoelectric focusing, separated each major isoenzyme into doublets of similar Mr values. Pancreatic and tumour-derived alpha-amylases had similar Km and Ki (alpha-GHI) values, but the specific activity of the tumour alpha-amylase was approximately two-thirds that of the normal alpha-amylase. Although amino acid analysis and peptide mapping with the use of CNBr, N-chlorosuccinimide or Staphylococcus aureus V8 proteinase gave comparable profiles for the two alpha-amylases, tryptic-digest fingerprint patterns were different. Antibodies raised against the purified pancreatic alpha-amylase and tumour alpha-amylase respectively showed only one positive band on immunoblotting after gel electrophoresis of crude extracts of rat pancreas and carcinoma, at the same position as that of the purified enzyme. More than 95% of the alpha-amylase activity in the pancreas and in the tumour was absorbed by an excess amount of either antibody, indicating that normal and tumour alpha-amylases are immunologically identical. The presence of additional isoenzymes in the carcinoma, and dissimilarity of tryptic-digest patterns, may reflect an alteration in gene expression or in the post-translational modification of this protein in this heterogeneously differentiated transplantable pancreatic acinar carcinoma.     

Purification and Properties of α-Aminoadipate Aminotransferase from Rat Liver and Kidney Mitochondria

Abstract

Recently we reported an affinity chromatography method to purify α-aminoadipate aminotransferase (AadAT) activity from rat kidney supernatant fraction. Using the same affinity column, we purified AadAT activities from rat kidney and liver mitochondria. The physical and kinetic properties such as pH optima, Km for substrates, molecular weight, subunit structure, isoelectric pH, electrophoretic mobility and inhibition by dicarboxylic acids of mitochondrial AadAT were similar to those of the AadAT from rat kidney supernatant fraction. These results indicate that AadAT from different subcellular fractions is structurally and immunologically identical.     

Aldehyde dehydrogenase in 2-acetaminofluorene-induced rat hepatomas. Ontogeny and evidence that the new isoenzymes are not due to normal gene de-repression

The pre- and post-natal ontogeny of Sprague-Dawley rat liver aldehyde dehydrogenase [aldehyde-NAD(P)(+) oxidoreductase, EC 1.2.1.5] is described. At no time in its ontogenetic development does normal liver aldehyde dehydrogenase exhibit any of the characteristics of a series of unique aldehyde dehydrogenases that can be isolated from 2-acetamidofluorene-induced rat hepatomas. Enzyme activity is first detectable in 15-day foetal liver and gradually increases throughout pre- and post-natal development until adult activities are attained by day 49 after birth. Electrophoretically, normal aldehyde dehydrogenase, throughout its ontogeny, exists as the same single isoenzyme found in normal adult liver. Isoelectric points for two normal liver isoenzymes demonstrable by isoelectric focusing are pH5.9 and 6.0. The immunochemical properties of aldehyde dehydrogenase during its ontogeny are identical with those of normal adult liver aldehyde dehydrogenase when tested against anti-(hepatoma aldehyde dehydrogenase) serum in Ouchterlony double-diffusion tests. The results indicate that the hepatoma-specific aldehyde dehydrogenases are not the result of the de-repression of genes normally repressed in adult rat liver or in some other adult tissue.     

Purification and partial characterization of the glutathione S-transferases in carp liver, and their interaction with 2,4-dichlorophenoxyacetic acid and 1,4-benzoquinone

The hepatic glutathione S-transferase (GST) activity in the cytosol of the freshwater fish carp (Cyprinus carpio) was enriched by glutathione affinity chromatography. The anionic (GST A1-A3) and cationic (GST C1-C3) isoenzymes were then separated in two chromatofocusing steps. SDS electrophoresis showed GST C1 to be a heterodimer with subunits of Mr 25,000 and 28,000, and all other isoenzymes to be homodimers with subunits of Mr 25,400. They were partially characterized by different biochemical parameters. The water pollutants 2,4-dichlorophenoxyacetic acid and 1,4-benzoquinone inhibited all carp GST isoenzymes, following the same kinetic inhibition patterns as for rat liver GST. It is concluded that hepatic carp GST can play an important role in the detoxication of aquatic pollutants.