纳豆激酶粗提液的体外溶栓抑菌实验

目的探讨纳豆激酶粗提液的体外溶栓、抑菌作用.方法以大豆为培养基,米曲霉为菌种,发酵制得成熟纳豆,用不同饱和度(NH4)2SO4对粗提液进行盐析,所得沉淀溶于生理盐水中,用纤维蛋白平板法测定其活性,确定提取纳豆激酶的分级沉淀范围.用体外溶栓法测纳豆激酶粗提液的体外溶栓作用.用平板打孔法及纸片扩散法测不同浓度纳豆抑菌物质的体外抑大肠杆菌作用.结果纳豆激酶的(NH4)2SO4分级沉淀范围选择在60%.纳豆激酶粗提液对血块的溶解作用较同样活力大小的尿激酶强.纳豆抑菌物质粗提液对大肠杆菌都具有一定的体外抑制作用,当浓度大于50%,抑菌圈直径随着浓度的增高而增大.结论纳豆激酶粗提液具有较好的体外溶栓作用,并对大肠杆菌具有一定的抑制作用.     

药食两用纳豆激酶的研究进展

本文从血栓栓塞疾病的形成机制为依据,综述了纳豆激酶的药理作用。介绍了国内外产纤溶酶菌株的筛选方法,纳豆激酶的分离、纯化常用技术,纳豆激酶的生理生化特性、活性测定方法。并说明了影响纳豆激酶稳定的4个因素,和增加纳豆激酶产量的有效方法。通过药食两用纳豆激酶的研究进展,希望对纳豆激酶的研究提供理论基础。     

纳豆激酶酶原基因和纳豆激酶基因的克隆及在大肠杆菌中表达

目的：构建可高效生产有活性的纳豆激酶的大肠杆菌工程菌。方法：将纳豆激酶酶原（pro-nattokinase,pro-NK)基因和纳豆激酶（natokinase,NK)基因,并分别克隆到表达融合蛋白的高效表达载体pJN上,构建出表达质粒pJNK1和pJNK2,并转化大肠杆菌BL21（DE3）。结果：IPTG诱导下,两个融合蛋白的表达量均达到30%,活性检测显示表达纳豆激酶酶原融合蛋白的菌株pJNK-1(BL)诱导后菌体破碎上清的溶栓活性比表达纳豆激酶融合蛋白的菌株pJNK-2(BL)高2-3倍,结论：纳豆激酶酶原融合蛋白部分自减切产生纳豆激酶成熟肽。     

纳豆芽孢杆菌菌种纯化及不同氮源对其产纳豆激酶的影响

纳豆激酶(nattokinase, NK)是一种由纳豆芽孢杆菌发酵产生的丝氨酸蛋白酶,具有良好的纤溶活性。本研究从wako Nattokinase中分离纯化出高品质的纳豆芽孢杆菌,旨在探究最适宜该菌产纳豆激酶的发酵培养基氮源。研究人员选择了6种氮源对其进行发酵实验,通过连续测定发酵液的菌量、pH和纤溶活性以观察不同氮源对纳豆芽孢杆菌产纳豆激酶的影响。研究结果表明:最优氮源为乳清蛋白,在以此为氮源的培养基中发酵培养120 h后,纳豆激酶的纤溶活性高达1 757.79 U/mL。以乳清蛋白发酵培养基对纳豆芽孢杆菌进行发酵,不仅可以得到高活性的纳豆激酶,还可为纳豆激酶应用于食品、保健品领域提供思路。     

纳豆激酶生产菌的筛选及发酵纳豆特性研究

为开发具有特定生理活性的新型纳豆保健品,从发酵豆制品中分离筛选得到一株纳豆激酶高产菌株。利用该菌株以及市售的3种纳豆中的纳豆菌进行纳豆发酵,比较了4株纳豆菌发酵纳豆的特性,并对纳豆激酶活性进行分析。结果表明5号菌株发酵生产纳豆周期短,颜色金黄,具有酱香味,拉丝长度最佳。同时,对产纳豆激酶的最佳发酵时间进行研究,结果表明发酵至17 h纳豆激酶活性达到最大值。     

纳豆激酶基因工程研究进展

纳豆激酶是由纳豆芽孢杆菌(Bacillussubtillisnatto)分泌的一种具有纤溶作用的碱性丝氨酸蛋白酶。对纳豆激酶基因的克隆与表达,基因与蛋白质结构以及基因工程纳豆激酶的特性和功能进行了综述。     

纳豆激酶基因的表达及纯化

利用PCR方法从分泌纳豆激酶的枯草杆菌基因组DNA中扩增得到纳豆激酶基因(NK),利用基因重组技术构建了纳豆激酶基因的表达载体pETNK。在诱导下,实现了在大肠杆菌中高效表达,经SDS-PAGE电泳分析和薄层扫描结果显示,表达的目的蛋白占菌体蛋白的21．5％。将表达产物经过DEAE-Cellulos-DE52和Sephedax-G100两个柱分离纯化,得到纯的纳豆激酶蛋白干粉,经琼脂糖-纤维蛋白平板法测出纳豆激酶干粉的溶栓活性相当于200u尿激酶。从基因工程角度研究纳豆激酶基因的克隆、表达及纯化,为用基因工程菌生产纳豆激酶奠定了基础。     

纳豆激酶基因在大肠杆菌中活性表达的比较研究

实现纳豆激酶基因 (nattokinasegene)在大肠杆菌中高活性表达 ,并说明前肽 ( pro序列 )对纳豆激酶的活性表达必不可少。以纳豆芽孢杆菌基因组DNA为模板 ,采用PCR方法分别扩增编码信号肽、前肽及成熟肽的序列 ( pre pro NK)和编码前肽、成熟肽的序列 (pro NK) ,构建了大肠杆菌表达质粒 pTYB1 0 1 ,pTYB1 0 2 ,转化大肠杆菌ER2 5 66。在IPTG诱导下 ,分别在 1 5℃ ( 1 4h) ,3 0℃ ( 3h)和 3 7℃ ( 2h)培养。结果可见 ,pTYB1 0 2能表达有活性的纳豆激酶。SDS PAGE表明 ,1 5℃表达杂蛋白更少。薄层扫描显示表达的纳豆激酶占菌体总蛋白的 3 0 %以上。成功制备了表达纳豆激酶的工程菌。     

产纳豆激酶菌株Bacillus sp.ZLK08的分离及酶纯化

获得稳定产纳豆激酶菌株,为高酶活纳豆激酶产生菌的改造奠定基础.取各来源纳豆,用平板梯度稀释法分离菌株,测定菌株酶活,利用16S rDNA鉴定产酶菌株,凝胶过滤法纯化纳豆激酶并SDS-PAGE检测分析.成功获得稳定产酶芽胞杆菌Bacillus sp.ZLK08,16S rDNA分析表明其与GenBank中序列同源率达到99％,液体发酵表明酶活达到2.5 FU/mL,经纯化,SDS-PAGE表明纳豆激酶分子量为28.46 ku.分离出的Bacillus sp.ZLK08菌株能稳定产纳豆激酶且具有较高酶活.     

纳豆激酶的研究进展

纳豆激酶是一种由纳豆芽孢杆菌产生的具有强溶纤作用的碱性丝氨酸蛋白酶,具有安全性好、半衰期长、口服有效等优点.就纳豆激酶的结构、理化性质、功能、溶栓机制、酶活性测定、分离纯化以及纳豆激酶的应用现状及发展前景等方面进行了综述.     

Purification and characterization of dipeptidyl peptidase IV from Streptococcus salivarius HHT.

Dipeptidyl peptidase IV (DAP IV) was purified from Streptococcus salivarius HHT by anion-exchange chromatography, gel filtration and affinity chromatography after lysis of cell walls with N-acetylmuramidase. DAP IV was purified 114-fold with a yield of 16.6% from total activity of the crude extract. The purified enzyme was shown to be homogeneous by disc gel electrophoresis. The molecular weight of the enzyme was estimated to be about 109,000 by gel filtration and 47,000 by sodium dodecylsulphate SDS-polyacrylamide gel electrophoresis, suggesting that the native enzyme is a dimeric form. The optimum pH for the reaction was 8.7 in Gly-NaOH buffer, and the isoelectric point of the enzyme was pH 4.2. The enzyme hydrolysed specifically N-terminal X-Pro from X-Pro-p-nitroanilides. The enzyme activity was hardly affected by various cations, sulphydryl-blocking reagents and metal chelators. The enzyme activity was markedly inhibited by 1 mM diisopropylfluoride, and the desialysed enzyme was attacked by proteinases.     

Purification and characterization of aquacobalamin reductase (NADPH) from Euglena gracilis

Euglena aquacobalamin reductase (NADPH: EC 1.6.99.-) was purified, and its subcellular distribution was studied to elucidate the mechanism of the conversion of hydroxocobalamin to 5'-deoxyadenosylcobalamin. The enzyme was found in the mitochondria. It was purified about 150-fold over the Euglena mitochondrial extract in a yield of 38%. The purified enzyme was homogeneous in polyacrylamide gel electrophoresis. Spectra of the purified enzyme showed that it was a flavoprotein. The molecular weight of the enzyme was calculated to be 66,000 by Sephadex G-100 gel filtration and 65,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was specific to NADPH with an apparent Km of 43 microM and to hydroxocobalamin with an apparent Km of 55 microM. The enzyme did not require FAD or FMN as a cofactor. The optimum pH and temperature were 7.0 and 40 degrees C, respectively.     

Purification and partial characterization of glycogen synthase kinase-3 from rabbit liver

Summary Glycogen synthase kinase-3 (GSK-3) was purified from rabbit liver to homogeneity by ultracentrifugation, ion-exchange chromatography on DEAE-cellulose, Cellulose phosphate, CM-Sephadex and Fast Protein Liquid Chromatography (FPLC) on Mono-S column. The enzyme was purified approximately 20,000 fold with an approximate 2% recovery. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis. GSK-3 is a monomeric enzyme with a molecular weight of 50,000–52,000 as derived from SDS-polyacrylamide gel electrophoresis and gel filtration. The purified enzyme was indeed a GSK-3 since it phosphorylated three sites, i.e., 3a, 3b, and 3c on liver glycogen synthase. GSK-3 incorporated up to 2.6 mol Pi/mol glycogen synthase subunit with a concomitant inactivation of glycogen synthase activity.     

Purification and characterization of acid trehalase from the yeast suc2 mutant

Acid trehalase was purified from the yeast suc2 deletion mutant. After hydrophobic interaction chromatography, the enzyme could be purified to a single band or peak by a further step of either polyacrylamide gel electrophoresis, gel filtration, or isoelectric focusing. An apparent molecular mass of 218,000 Da was calculated from gel filtration. Polyacrylamide gel electrophoresis of the purified enzyme in the presence of sodium dodecyl sulfate suggested a molecular mass of 216,000 Da. Endoglycosidase H digestion of the purified enzyme resulted after sodium dodecyl sulfate gel electrophoresis in one distinct band at 41,000 Da, representing the mannose-free protein moiety of acid trehalase. The carbohydrate content of the enzyme was 86%. Amino acid analysis indicated 354 residues/molecule of enzyme including 9 cysteine moieties and only 1 methionine. The isoelectric point of the enzyme was estimated by gel electrofocusing to be approximately 4.7. The catalytic activity showed a maximum at pH 4.5. The activity of the enzyme was not inhibited by 10 mM each of HgCl2, EDTA, iodoacetic acid, phenanthrolinium chloride or phenylmethylsulfonyl fluoride. There was no activation by divalent metal ions. The acid trehalase exhibited an apparent Km for trehalose of 4.7 +/- 0.1 mM and a Vmax of 99 mumol of trehalose min-1 X mg-1 at 37 degrees C and pH 4.5. The acid trehalase is located in the vacuoles. The rabbit antiserum raised against acid trehalase exhibited strong cross-reaction with purified invertase. These cross-reactions were removed by affinity chromatography using invertase coupled to CNBr-activated Sepharose 4B. Precipitation of acid trehalase activity was observed with the purified antiserum.     

Purification and some properties of ornithine decarboxylase from rat liver

Ornithine decarboxylase (EC 4.1.1.17) was purified to near homogeniety from livers of thioacetamide- and dl-α-hydrazino-δ-aminovaleric acid-treated rats by using three types of affinity chromatography with pyridoxamine phosphate-Sepharose, pyridoxamine phosphate-dipropylenetriamine-Sepharose and heparin-Sepharose. This procedure gave a purification of about 3.5·10⁵-fold with an 8% yield; the specific activity of the final enzyme preparation was 1,1·10⁶ nmol CO₂/h per mg protein. The purified enzyme gave a single band of protein which coincided with activity peak on polyacrylamide gel electrophoresis and also gave a single major band on SDS-polyacrylamide gel electrophoresis. A single precipitin line was formed between the purified enzyme and an antiserum raised against a partially purified enzyme, on Ouchterlony immunodiffusion. The molecular weight of the enzyme was estimated to be 105 000 by polyacrylamide gel electrophoresis at several different gel concentrations; the dissociated subunits had molecular weights of 50 000 on SDS-polyacrylmide gels. The isoelectric point of the enzyme was pH 4.1.     

Purification and characterization of a novel nucleoside phosphorylase from a Klebsiella sp. and its use in the enzymatic production of adenine arabinoside

An adenosine-assimilating bacterium, Klebsiella sp. strain LF1202, inducibly formed a novel nucleoside phosphorylase which acted on both purine and pyrimidine nucleosides when the cells were cultured in medium containing adenosine as a sole source of carbon and nitrogen. The enzyme was purified (approximately 83-fold, with a 17% activity yield) to the homogeneous state by polyacrylamide gel electrophoresis. The molecular weight of the purified enzyme was calculated to be 125,000 by gel filtration of Sephadex G-200 column chromatography, although the enzyme migrated as a single protein band with a molecular weight of 25,000 on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis; thus, it was thought to consist of five identical subunits. Besides purine nucleosides (adenosine, inosine, and guanosine), the purified enzyme also acted on pyrimidine nucleosides such as uridine, 2'-deoxyuridine, and thymidine. The purified enzyme catalyzed the synthesis of adenine arabinoside, a selective antiviral pharmaceutic agent, from uridine arabinoside and adenine.     

Renal angiotensin I-converting enzyme as a mixture of sialo- and asialo-enzyme, and a rapid purification method.

Angiotensin I-converting enzyme [EC 3.4.15.1] was rapidly and highly purified from a particulate fraction of hog kidney cortex with 13% yield. The procedure, which was rapid, included fractionation on DEAE-cellulose and calcium phosphate gel, chromatographies on DEAE-Sephadex A-50 and hydroxylapatite columns, and gel filtration on a Sephadex G-200 column. The purified enzyme preparation gave two protein bands on standard disc gel electrophoresis, but showed a single protein component on the gel after treatment with neuraminidase [EC 3.2.1.18]. The data strongly suggest that the purified enzyme preparation was a mixture of sialo- and asialo-enzyme. Sialic acid residues apparently do not contribute to the catalytic activity of the enzyme. The enzyme was activated more by chloride ions than by other halide ions tested, using Bz-Gly-Gly-Gly as a substrate. The dissociation constant for chloride ions was determined to be 2.2 mM. Chloride did not protect the enzyme against heat or low pH. The enzyme was resistant to inactivation by trypsin [EC 3.4.21.4] and chymotrypsin [EC 3.4.21.1].     

Purification and properties of beta-N-acetylglucosaminidase from Escherichia coli.

beta-N-acetylglucosaminidase (EC 3.2.1.30) has been purified from Escherichia coli K-12 to near homogeneity based on polyacrylamide gel electrophoresis in both 0.5% sodium dodecyl sulfate and in 6 M urea at pH 8.5. The purified enzyme shows a pH optimum of 7.7 and the Km for p-nitrophenyl-beta-D-2-acetamido-2-deoxyglucopyranoside is 0.43 mM. The molecular weight of this enzyme, determined by both Sephadex gel filtration and by sodium dodecyl sulfate gel electrophoresis, is equivalent to 36,000. It is shown to be a soluble cytoplasmic enzyme. Studies on the substrate specificites of the purified enzyme indicate that this enzyme is an exo-beta-N-acetylglucosaminidase.     

Purification and multiple forms of human placental alkaline phosphatase

The commercially available human placental alkaline phosphatase was purified to near homogeneity. Multiple bands of the purified enzyme were resolved in the polyacrylamide gel. The number of bands in the gel was reduced after the enzyme was treated with neuraminidase.     

Complete purification and immunochemical analysis of S-adenosylmethionine synthetase from bovine brain

We have purified S-adenosylmethionine (AdoMet) synthetase about 3000-fold from bovine brain extract. The Km values of the enzyme for L-methionine and ATP were 10 and 50 microM, respectively. An apparent molecular mass of the enzyme was estimated to be 160 kDa by gel filtration on a Sephacryl S-200 column. Sucrose density gradient centrifugation gave a sedimentation coefficient of 8 S. Polyacrylamide gel electrophoresis of the purified enzyme in native system revealed a single protein band, whereas two polypeptide bands with molecular masses of 48 kDa (p48) and 38 kDa (p38) were observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme. Antibody against bovine brain AdoMet synthetase was prepared by injecting the purified enzyme into a rabbit. Immunoblot analysis revealed that the antibody recognized both p48 and p38 in the impure enzyme preparations from bovine brain as well as in the purified enzyme. Specific antibodies against p48 and p38 were separated from the immunoglobulin fraction by an affinity purification, both of which inhibited the enzyme activity. These results indicate that AdoMet synthetase from bovine brain consists of two different polypeptides, p48 and p38.