耐热醋酸棱状芽孢杆菌中具有高的二硫键还原活性组分的提取和…

用ＤＥＡＥ－Ｓｅｐｈａｒｏｓｅ ＣＬ－６Ｂ层析柱从Ｃ．ｔｈｅｒｍｏａｃｅｔｉｃｕｍ细胞提取物中分离出的两个具有相近分子量（７００）的活性组分，在ＭＶ＾＋存在下，对二硫键具有高的催化还原活性。这两组分参与的催化还原反应不以ＮＡＤ（Ｐ）Ｈ为电子供体。在实验条件下，对二硫键的催化还原活性顺序为：ＧＳＳＧ〉硫辛酰胺〉胱氨酸〉胱氨酸〉硫辛酸。活性组分具有较高的反应稳定性和热稳定性。两组分在２６０、３５４和５     

豆薯种子中两种蛋白质的分离纯化及其性质研究

豆薯（Ｐａｃｈｙｒｒｈｉｚｕｓｅｒｏｓｕｓ）种子经磷酸盐缓冲液抽提,Ｓ－ＳｅｐｈａｒｏｓｅＦａｓｔＦｌｏｗ柱,ＤＥ－５２纤维素柱和ＳｅｐｈａｄｅｘＧ－７５柱层析,提取出两种高纯度的蛋白成分,命名为ＰａｃｈｙｒｉｎⅠ和Ⅱ．ＳＤＳ－ＰＡＧＥ测得其分子量分别为３３ｋＤ和１４．５ｋＤ,但ＨＰＬＣ分子筛的结果显示ＰａｃｈｙｒｉｎⅡ的分子量为２８ｋＤ,无论在还原条件下,还是在非还原条件下,ＰａｃｈｙｒｉｎⅡ电泳的结果都完全相同,表明该蛋白的亚基不是以二硫键相连。两种蛋白的等电点分别为４．５和６．５．用酸解法测定了它们的氨基酸组成。在无细胞体系中,它们对蛋白合成有较弱的抑制活性,显示它们可能是核糖体失活蛋白（ＲＩＰｓ）家族中的新成员。     

昆虫谷胱甘肽S-转移酶分离纯化的新方法

谷胱甘肽Ｓ－转移酶（ｇｌｕｔａｔｈｉｏｎｅＳ－ｔｒａｎｓｆｅｒａｓｅｓ,ＧＳＴ）是一类具有多种生理功能的同功酶．从蜡螟幼虫（Ｇａｌｅｒｉａｍｅｌｏｎｅｌａ）的提取液中分离纯化谷胱甘肽Ｓ－转移酶的基本方法如下：首先将冷冻的蜡螟幼虫在磷酸缓冲液中匀桨,经１００００ｇ和１０００００ｇ分级离心;取上清液通过ＱＡＥ－ＳｅｐｈａｄｅｘＡ－２５离子交换柱层析除去部分色素和杂蛋白;然后采用谷胱甘肽－琼脂糖凝胶亲和层析（ＧＳＨ－ＱＴ４）,四溴酚酞二磺酸盐－琼脂糖凝胶亲和层析（ＢＳＰ－ＱＴ４）,铜离子－琼脂糖凝胶螯合层析（Ｃｕ２＋－ＱＴ４）及ＰＢＥ９４－Ｓｅｐｈａｒｏｓｅ（ＰＢＥ９４）聚焦层析等层析技术进一步分离纯化．将上述方法获得的色谱峰以ＣＤＮＢ和ＤＣＮＢ为底物检测生物活性．具有生物活性部分的蛋白质,通过ＳＤＳ－ＰＡＧＥ测定其分子量．实验结果表明,采用ＧＳＨ－ＱＴ４亲和层析法获得的活性峰,在ＳＤＳ－ＰＡＧＥ图谱上呈现出两条带,分子量为２４ｋＤ,２４．５ｋＤ左右;Ｃｕ２＋－ＱＴ６螯合层析法分离的活性峰,呈现出一条带,分子量为２４ｋＤ左右;ＰＢＥ９４－聚焦层析法分离获得三个活性峰：第一色谱峰,呈现出一条带,分子量为２３ｋＤ左右     

重组RA—538及反义c—myc腺病毒对人胃癌,食管癌和bcl—2高表达细胞系的作用

本课题研究ＲＡ５３８、反义c-ymc重组腺病毒对人胃癌（ＳＧＣ７９０１）、食管癌（Ｅ Ｃ１０９、ＥＣ８７１２）、正常人胚肺２ＢＳ（２ＢＳ）及ｂｃｌ－２高表达细胞第的体仙外生物学作用及其分子机制。结果显示Ａｄ－ＲＡ５３８及Ａｄ－ＡＳｃ－ｍｙｃ对ＳＧＣ７９０１细胞体内外均具有明显的生长抑制及凋亡诱导作用,并能抑制其ｃ－ｍｙｃ、ｂｃｌ－２、ｃｙｃｌｉｎＤ１基因的表达及刺激ｂａｘ基因的表达。对ＥＣ１０９、ＥＣ８     

湖南尖吻蝮蛇毒两个出血毒素的纯化和理化性质

经ＳｅｐｈａｄｅｘＧ－７５凝胶过滤,ＱＡＥ－ＳｅｐｈａｄｅｘＡ－５０和ＣＭ－ＳｅｐｈａｄｅｘＣ－２５离子交换层析的步骤,从湖南产尖吻蝮（Ｄｉｅｎａｇｋｉｓｔｒｏｄｏｎａｃｕｔｕｓ）蛇毒中纯化出两个出血毒素（ＤａＨＴ－１和ＤａＨＴ－２）．ＳＤＳ－ＰＡＧＥ测得分子量均为２３．５ｋＤ,ＩＥＦ－ＰＡＧＥ测得等电点分别为５．６和５．２,两者具有相似的氨基酸组成,其中酸性氨基酸（Ａｓｘ,Ｇｌｘ）分别占２３％和２４％,ＤａＨＴ－１和ＤａＨＴ－２的最小出血剂量（ＭＨＤ）分别为０．５μｇ和０．８μｇ。都具蛋白水解酶活性,无对ＴＡＭＥ,ＢＡＥＥ的水解活性和ＰＬＡ２酶活性．两者的蛋白水解酶活力与出血活性并非正相关．ＤａＨＴ－１和ＤａＨＴ－２的最适温度分别为３５℃和４０℃,最适ｐＨ为６－９,对热均不稳定,温度高于６０℃活性完全丧失。金属离子的分析显示每摩尔毒素蛋白约含０．５ｍｏｌ的Ｚｎ,１ｍｏｌ的Ｃａ,较多的Ｎａ、Ｋ、Ｍｇ,不含Ｃｏ。     

地衣芽孢杆菌β—甘露聚糖酶的纯化及其性质的研究

地衣芽孢杆菌１Ｂａｃｉｕｕｓ Ｌｉｃｈｅｎｉｆｏｒｍｉｓ）ＢＬ－３０６产生的胞外β－甘露聚糖酶经硫酸铵分级盐析,ＤＥＡＥ－纤维素柱层析。Ｓｅｐｈａｄｅｘ－Ｇ１００柱凝胶过滤和ＤＥＡＥ－纤维素柱再层析分离纯化,得到ＳＤＳ－聚丙烯酰胺凝胶电泳（ＳＤＳ－ＰＡＧＥ）均一样品。用ＳＤＳ－ＰＡＧＥ测得纯化后β－甘露聚糖酶分子量为２６０００道尔顿。用凝胶等电聚焦电泳（ＰＡＧＥＩＥＦ）测得等电点ＰＩ为５．０。该酶     

枯草芽孢杆菌中性内切β-甘露聚糖酶的纯化及性质

三草芽孢杆菌（Ｂａｃｉｌｌｕｓ ｓｕｂｔｉｌｉｓ）ＢＭ９６０２产生的中性内切β－甘露聚糖酶（ｅｎｄｏ－β－１,４－Ｄ－ｍａｎｎａｎ ｍａｎｎａｎｏｈｙｄｒｏｌａｅｓ,ＥＣ,３．２．１．７８）经硫酸铵分级沉淀、ＤＥＡＥ－纤维素（ＤＥ２２）离子交换柱层析,得到电泳纯的样品,提纯了４５．５倍,收率为５．９％。用ＳＤＳ－ＰＡＧＥ测得该酶的分子量为３５ｋＤ。用ＰＡＧＥＩＥＦ测得其等电点ｐⅠ为４．５。酶反应的     

THINOPYRUM BESSARABICUM和THINOPYRUM ELONGATUM的基 …

对２个八倍体Ｃ．Ｓ－Ｔｈｉｎｏｐｙｒｕｍ ｂｅｓｓａｒａｂｉｃｕｍ（ＡＡＢＢＤＤＪＪ,２ｎ＝８ｘ＝５６）和Ｇｏｓｈａｗｋ（ＧＨＫ）－Ｔｈｉｎｏｐｙｒｕｍ ｅｌｏｎｇａｔｕｍ（ＡＡＢＢＤＤＥＥ,２ｎ＝８ｘ＝５６）的根尖细胞染色体进行Ｃ－分带,从中分检出Ｔｈ．ｂｅｓｓａｒａｂｉｃｕｍ和Ｔｈ．ｅｌｏｎｇａｔｕｍ的各自染色体进行核型分析,结果表明：Ｔｈ．ｂｅｓｓａｒａｂｉｃｕｍ和Ｔｈ．ｅｌｏｎｇａｔｕｍ的     

亲和层析纯化HepG_2细胞分泌的PAI－1

本文报道用抗ＰＡＩ－１单克隆抗体（ＭｃＡｂ）亲和层析建立了纯化ＰＡＩ－１的简便方法。经免疫亲和层析,ＳｅｐｈａｃｒｙｌＳ２００凝胶过滤,从ＨｅｐＧ２细胞培液中分离到糖基化和非糖基化两种形式的ＰＡＩ－１,回收率为８４％,ＰＡＩ－１比活性６．１×１０４ＩＵ／ｍｇ。糖基化ＰＡＩ－１分子量为５０ｋＤ,比活性５．８×１０４ＩＵ／ｍｇ。非糖基化ＰＡＩ－１分子量４３ｋＤ,占总ＰＡＩ－１３０％,仍具有ＰＡＩ－１活性。用ＣｏｎＡ－Ｓｅｐｈａｒｏｓｅ亲和层析进一步纯化得到ＳＤＳ－ＰＡＧＥ纯的糖基化ＰＡＩ－１。     

人食管鳞状上皮癌糖复合物表达的研究

凝集素可与其相对应的糖复合物特异性结合。在癌症形成过程中细胞表面经历着显著的变化,本文用十种生物素化凝集素即ＵＥＡ－Ｉ、ＲＣＡ－Ｉ、ＤＢＡ、ＰＳＡ、ＰＮＡ、ＢＳＬ、ＬＣＡ、ＷＧＡ、ＣｏｎＡ和ＳＢＡ作为探针,对正常食管上皮和食管鳞状上皮癌进行研究,以确定正常食管上皮和食管鳞状上皮癌中糖复合物的改变,结果发现,ＰＮＡ和ＰＳＡ在正常食管和食管鳞状上皮癌中均无反应,ＲＣＡ－Ｉ、ＤＢＡ、ＢＳＬ、ＬＣＡ、ＣｏｎＡ和ＳＢＡ受体在正常和癌组织中有着特征性变化,ＢＳＬ和ＤＢＡ在食管中无反应,ＬＣＡ、ＳＢＡ和ＲＣＡ－１正常食管和食管鳞状上皮癌中反应方式不同,ＣｏｎＡ和ＷＧＡ则在同一癌组织的不同部位都显示出不同的反应。尽管ＵＥＡ－Ｉ在正常食管和食管鳞状上皮癌均呈阳性反应,但似乎未表现出有意义的变化。上述结果提示食管癌的发生与含α－Ｄ－ＧａｌＮＡｃ（ＤＢＡ和ＳＢＡ）、β－Ｄ－Ｇａｌ／β－Ｎ－ａｃｅｔｙｌ－Ｄ－Ｇａｌａｃｔｏｓａｍｉｎｅ（ＲＣＡ－Ｉ）、α－Ｄ－Ｇｌｃ／α－Ｄ－Ｍａｎ（ＬＣＡ和ＣｏｎＡ）、［β－（１－４）－Ｄ－ＧｌｃＮＡｃ］２／ＮｅｕＮＡｃ（ＷＧＡ）和α－Ｄ－Ｇａｌ（ＢＳＬ）等的糖复合物的改变有较为密切的关系。     

Maturation of lipoprotein lipase. Expression of full catalytic activity requires glucose trimming but not translocation to the cis-Golgi compartment.

The relationship between maturation of lipoprotein lipase (LPL) and its translocation from the endoplasmic reticulum (ER) to the Golgi complex was determined by measuring lipolytic activity under conditions preventing transport of the enzyme from the ER to the Golgi compartment. In the presence of brefeldin A, a reagent that inhibits movement of proteins from the ER and causes the disassembly of the Golgi complex, pro-5 Chinese hamster ovary cells accumulated catalytically active LPL, while secretion of the enzyme was effectively blocked. LPL retained intracellularly by brefeldin A treatment possessed oligosaccharide chains that were processed to the complex form by the Golgi enzymes redistributed into the ER. At 16 degrees C, a condition disrupting protein transport to the cis-Golgi, the retained enzyme again remained catalytically active although the oligosaccharides remained in the high mannose form. Lastly, attachment of the specific ER retention signal KDEL (Lys-Asp-Glu-Leu) to the carboxyl terminus of LPL also resulted in intracellularly retained enzyme that was fully active. The importance of oligosaccharide processing for attainment of LPL catalytic activity in vitro was also determined. LPL was active and secreted when trimming of the mannose residues was inhibited by deoxymannojirimycin and when addition of complex sugars was blocked using Chinese hamster ovary mutants (lec1 and lec2), indicating that these processing events are not necessary for the expression of a functional enzyme. However, blocking glucose removal by glucosidase inhibitors (castanospermine and N-methyl-deoxynojirimycin) resulted in a significant reduction in LPL specific activity and secretion. Thus, glucose trimming of LPL oligosaccharides is essential for enzyme activation; however, further oligosaccharide processing or translocation of the enzyme to the cis-Golgi is not required for full expression of lipolytic activity in vitro.     

Regulation and state of aggregation of Bacillus subtilis prephenate dehydratase in the presence of allosteric effectors.

Prephenate dehydratase from Bacillus subtilis was found to exist in three states of aggregation. A high molecular weight (210,000) species was fully active and the catalytic activity was unaffected by the effectors methionine or phenylalanine. Low concentrations of phenylalanine caused dissociation to a Mr = 55,000 dimer. Heating to 32 degrees C also caused dissociation, but cooling and adding substrate or methionine favored association. When no effectors were present the enzyme eluted from Sephadex columns as a monomer. Both methionine and phenylalanine shifted the equilibrium from the inactive monomer to the active dimeric enzyme. In the presence of a saturating methionine concentration, the dimer possessed the same high activity as did the 210,000-dalton form. Phenylalanine inhibited the dimer, but not the higher molecular weight form. A model involving only three types of sites (catalytic, association-activation, and inhibition) is consistent with the data. It is proposed that phenylalanine is the preferred metabolite for binding both effector sites on the dimer; it binds the association-activation site with higher affinity than the inhibition site, but binding at the latter site has a greater effect on the catalytic rate. Methionine, like phenylalanine, has a hydrophobic side chain but is accommodated only at the association-activation site.     

Structural properties of cyanase. Denaturation, renaturation, and role of sulfhydryls and oligomeric structure in catalytic activity

Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to give ammonia and bicarbonate. The enzyme is composed of 8-10 identical subunits (Mr = 17,008). The objective of this study was to clarify some of the structural properties of cyanase for the purpose of understanding the relationship between oligomeric structure and catalytic activity. Circular dichroism studies showed that cyanase has a significant amount of alpha-helix and beta-sheet structure. The one sulfhydryl group per subunit does not react with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) unless cyanase is denatured. Denaturation is apparently complete in 10 M urea or 6 M guanidine hydrochloride, but is significantly reduced in 10 M urea by the presence of azide (analog of cyanate) and is incomplete in 8 M urea. Denatured cyanase could be renatured and reactivated (greater than 85%) by removal of denaturants. Reactivation was greatly facilitated by the presence of certain anions, particularly bicarbonate, and by high ionic strength and protein concentration. The catalytic activity of renatured cyanase was associated only with oligomer. Cyanase that had been denatured in the presence of DTNB to give a cyanase-DTNB derivative could also be renatured at 26 degrees C to give active cyanase-DTNB oligomer. The active oligomeric form of the cyanase-DTNB derivative could be converted reversibly to inactive dimer by lowering the temperature to 4 degrees C or by reduction of the ionic strength and removal of monoanions. These results provide evidence that free sulfhydryl groups are not required for catalytic activity and that catalytic activity may be dependent upon oligomeric structure.     

Diethylpyrocarbonate reactivity ofKlebsiella aerogenes urease: Effect ofpH and active site ligands on the rate of inactivation

Reaction ofKlebsiella aerogenes urease with diethylpyrocarbonate (DEP) led to a pseudo-first-order loss of enzyme activity by a reaction that exhibited saturation kinetics. The rate of urease inactivation by DEP decreased in the presence of active site ligands (urea, phosphate, and boric acid), consistent with the essential reactive residue being located proximal to the catalytic center. ThepH dependence for the rate of inactivation indicated that the reactive residue possessed apK _a of 6.5, identical to that of a group that must be deprotonated for catalysis. Full activity was restored when the inactivated enzyme was treated with hydroxylamine, compatible with histidinyl or tyrosinyl reactivity. Spectrophotometric studies were consistent with DEP derivatization of 12 mol of histidine/mol of native enzyme. In the presence of active site ligands, however, approximately 4 mol of histidine/mol of protein were protected from reaction. Each protein molecule is known to possess two catalytic units; hence, we propose that urease possesses at least one essential histidine per catalytic unit.     

Diethylpyrocarbonate reactivity ofKlebsiella aerogenes urease: Effect ofpH and active site ligands on the rate of inactivation

Reaction ofKlebsiella aerogenes urease with diethylpyrocarbonate (DEP) led to a pseudo-first-order loss of enzyme activity by a reaction that exhibited saturation kinetics. The rate of urease inactivation by DEP decreased in the presence of active site ligands (urea, phosphate, and boric acid), consistent with the essential reactive residue being located proximal to the catalytic center. ThepH dependence for the rate of inactivation indicated that the reactive residue possessed apK _a of 6.5, identical to that of a group that must be deprotonated for catalysis. Full activity was restored when the inactivated enzyme was treated with hydroxylamine, compatible with histidinyl or tyrosinyl reactivity. Spectrophotometric studies were consistent with DEP derivatization of 12 mol of histidine/mol of native enzyme. In the presence of active site ligands, however, approximately 4 mol of histidine/mol of protein were protected from reaction. Each protein molecule is known to possess two catalytic units; hence, we propose that urease possesses at least one essential histidine per catalytic unit.     

Biological protection by superoxide dismutase

Diol dehydrase from $\text{Aerobacter aerogenes}$ was dissociated into two different protein components or subunits, designated Components F and S, by chromatography on DEAE-cellulose. Neither component alone possessed any appreciable catalytic activity. Diol dehydrase activity was restored when the two components were combined. Both components were also required for inactivation of coenzyme B₁₂ by oxygen when incubation was carried out in the absence of substrate aerobically. The more acidic component, Component S, was a sulfhydryl protein sensitive to an alkylating agent, iodoacetamide. Coenzyme B₁₂ was not bound by the individual components, F or S, both of which were necessary for the cobamide binding. The presence of substrate, 1,2-propanediol, in eluting buffer retarded the dissociation of the enzyme.     

Phosphorylase phosphatase complex from skeletal muscle. Activation of one of two catalytic subunits by manganese ions

Sarcoplasmic phosphorylase phosphatase extracted from ground skeletal muscle was recovered in a high molecular weight from (Mr = 250000). This enzyme has been purified from extracts by anion-exchange and gel chromatography to yield a preparation with three major protein components of Mr 83000, 72000, and 32000 by sodium dodecyl sulfate gel electrophoresis. The phosphorylase phosphatase activity of the complex form was activated more than 10-fold by Mn2+, with a K0.5 of 10(-5) M, but not by Mg2+ or Ca2+. Manganese activation occurred over a period of several minutes and resulted primarily in an increase in Vmax of a phosphatase that was sensitive to trypsin. Activation persisted after gel filtration, and the active form of the enzyme did not contain bound manganese measured by using 54Mn2+. A contaminating p-nitrophenylphosphatase was activated by either Mn2+ (K0.5 of 10(-4) M) or Mg2+ (K0.5 of 10(-3) M). Unlike the protein phosphatase this enzyme was inactive following removal of the metal ions by gel filtration. The phosphatase complex could be dissociated into its component subunits by precipitation with 50% acetone at 20 degrees C in the presence of an inert divalent cation, reducing agent, and bovine serum albumin. Two catalytic subunits were quantitatively recovered; one of Mr 83000 was a trypsin-sensitive manganese-activated phosphatase and the second of Mr 32000 was trypsin-stable and metal ion dependent. Both enzymes were effective in catalyzing the dephosphorylation of either phosphorylase a or the regulatory subunit of adenosine cyclic 3',5'-phosphate (cAMP) dependent protein kinase, but neither subunit possessed p-nitrophenylphosphatase activity.     

Distribution of chymoelastases and trypsin-like enzymes in five species of entomopathogenic deuteromycetes

Nine isolates of the entomopathogenic deuteromycetes Metarhizium anisopliae, Beauveria bassiana, Verticillium lecanii, Nomuraea rileyi, and Aschersonia aleyrodis produced basic (pI greater than 7.0) chymoelastases that possessed extended binding sites, comprising at least four or five subsites, with preference for hydrophobic residues at the primary binding site. Most isolates also produced additional acidic enzymes with similar specificities against ester and amide substrates but which lacked activity against elastin. Both acidic and basic enzymes degraded high protein azure or locust cuticle and, as shown by inhibition studies, possessed essential serine and histidine residues in the active site. In spite of similarities in catalytic properties antibodies generated against a Metarhizium chymoelastase cross-reacted only with enzymes from two (out of four) Metarhizium isolates; enzymes from all other isolates did not cross-react. Two isolates of Metarhizium produced a third class of protease which degraded Bz-AA-AA-Arg-NA substrates (AA, various amino acids) and hide protein azure. Analogous peptidases were produced by other isolates but they were specific for Bz-Phe-Val-Arg-NA and showed less sensitivity to trypsin inhibitors. The possible significance to pathology of the presence of diverse yet similar protease forms in five genera of entomopathogens is discussed.     

The role of group bulkiness in the catalytic activity of psychrophile cold-active protein tyrosine phosphatase

The cold-active protein tyrosine phosphatase found in psychrophilic Shewanella species exhibits high catalytic efficiency at low temperatures as well as low thermostability, both of which are characteristics shared by many cold-active enzymes. The structure of cold-active protein tyrosine phosphatase is notable for the presence of three hydrophobic sites (termed the CA, Zn-1 and Zn-2 sites) behind the loop structures comprising the catalytic region. To identify the structural components responsible for specific enzyme characteristics, we determined the structure of wild-type cold-active protein tyrosine phosphatase at high resolution (1.1 A) and measured the catalytic efficiencies of enzymes containing mutations in the three hydrophobic sites. The bulkiness of the amino acid side chains in the core region of the Zn-1 site strongly affects the thermostability and the catalytic efficiency at low temperatures. The mutant enzyme I115M possessed a higher kcat at low temperatures. Elucidation of the crystal structure of I115M at a resolution of 1.5 A revealed that the loop structures involved in retaining the nucleophilic group and the acid catalyst are more flexible than in the wild-type enzyme.     

Chitosan as an active support for assembly of metal nanoparticles and application of the resultant bioconjugates in catalysis

Metal nanoparticle-chitosan (NPs-chitosan) bioconjugates were formed by exposure of chitosan to an aqueous solution of metal salts under thermal treatment. The metal nanoparticles that are formed strongly bound to chitosan, which encouraged us to investigate their catalytic performance. It was demonstrated that the metal NPs-chitosan bioconjugates functioned as effective catalysts for the reduction of 4-nitrophenol in the presence of NaBH₄, which was monitored by means of spectrophotometry as a function of reaction time. The silver NPs-chitosan bioconjugates exhibited excellent catalytic activity and were reusable for up to seven cycles. In contrast, the gold NPs-chitosan catalyst displayed poor catalytic activity, even in the second cycle. A highlight of our approach is that chitosan simultaneously acts as an active support for the synthesis and assembly of nanoparticles, and the resultant bioconjugates bear the advantage of easy separation from the reaction medium.