共查询到20条相似文献，搜索用时 671 毫秒
1.
蜱源抗凝分子及其作用机制 总被引：1，自引：0，他引：1
综述了血液凝固过程、血凝因子和血小板在血凝过程中的作用;总结了自1990年发现第一个蜱源抗凝血分子(TAP)以来分离鉴定出的蜱源抗凝血活性分子及其它们的抗凝机制及基于蜱抗凝多肽和cDNA克隆表达出的几种抗凝血分子,介绍了近年来在TAP的分子结构和抗凝机制方面的研究进展。 相似文献
2.
T J Girard L A MacPhail K M Likert W F Novotny J P Miletich G J Broze 《Science (New York, N.Y.)》1990,248(4961):1421-1424
Lipoprotein-associated coagulation inhibitor (LACI) appears to inhibit tissue factor (TF)-induced blood coagulation by forming a quaternary inhibitory complex containing factor Xa, LACI, factor VIIa, and TF. A genetically engineered hybrid protein consisting of the light chain of factor Xa and the first Kunitz-type inhibitor domain of LACI is shown to directly inhibit the activity of the factor VIIa-TF catalytic complex. Unlike inhibition of factor VIIa-TF activity by native LACI, inhibition by the hybrid protein is not dependent on factor Xa. In an assay of TF-induced coagulation, 50% TF inhibition occurs with hybrid protein at 35 nanograms per milliliter, whereas LACI at 2.5 micrograms per milliliter is required for an equivalent effect. gamma-Carboxylation of glutamic acid residues in the factor Xa light chain portion of the hybrid protein is required for inhibitory activity, indicating that the first Kunitz-type domain of LACI alone is not sufficient for inhibition of factor VIIa-TF. 相似文献
3.
鱿鱼肝脏活性肽的制备及生物活性研究 总被引：1，自引：0，他引：1
[目的]为鱿鱼肝脏的高值化利用提供基础研究数据。[方法]以鱿鱼肝脏蛋白为原料,通过蛋白酶水解来制备生物活性肽,研究了多种蛋白酶水解鱿鱼肝脏制得水解液的抗凝血活性、抑制血管紧张素Ⅰ转换酶（ACE）活性及抗氧化活性。[结果]当鱿鱼肝脏水解液浓度为5 mg/ml时,中性蛋白酶的水解液对ACE抑制率为68.0%;APTT值为59.8 s,TT值为34.2 s,比空白对照组分别延长26.7和20.6 s,表明鱿鱼肝脏的中性蛋白酶水解液具有抗凝血活性。中性蛋白酶解液对Fe3＋的还原力为0.588,羟自由基清除能力为64.5%,说明鱿鱼肝脏中性蛋白酶水解液具有较好的抗氧化活性;而其余的木瓜蛋白酶、酸性蛋白酶、碱性蛋白酶、胰蛋白酶的鱿鱼肝脏水解液的抗凝血活性和ACE抑制活性均低于中性蛋白酶水解液的酶解液活性。[结论]鱿鱼肝脏蛋白质具有较好的综合利用价值。 相似文献
4.
Molecular modeling of the HIV-1 protease and its substrate binding site 总被引：13，自引：0，他引：13
I T Weber M Miller M Jaskólski J Leis A M Skalka A Wlodawer 《Science (New York, N.Y.)》1989,243(4893):928-931
The human immunodeficiency virus (HIV-1) encodes a protease that is essential for viral replication and is a member of the aspartic protease family. The recently determined three-dimensional structure of the related protease from Rous sarcoma virus has been used to model the smaller HIV-1 dimer. The active site has been analyzed by comparison to the structure of the aspartic protease, rhizopuspepsin, complexed with a peptide inhibitor. The HIV-1 protease is predicted to interact with seven residues of the protein substrate. This information can be used to design protease inhibitors and possible antiviral drugs. 相似文献
6.
Alpha 2-antiplasmin Enschede: alanine insertion and abolition of plasmin inhibitory activity 总被引：8，自引：0，他引：8
W E Holmes H R Lijnen L Nelles C Kluft H K Nieuwenhuis D C Rijken D Collen 《Science (New York, N.Y.)》1987,238(4824):209-211
An abnormal alpha 2-antiplasmin that is associated with a serious bleeding tendency has been found in a Dutch family and is referred to as alpha 2-antiplasmin Enschede. This abnormal alpha 2-antiplasmin is converted from an inhibitor of plasmin to a substrate. The molecular defect of alpha 2-antiplasmin Enschede, as revealed by sequencing of cloned genomic DNA fragments, consists of an alanine insertion near the active site region of the molecule. Substitution of this fragment into complementary DNA for a wild-type alpha 2-antiplasmin yields a translation product with physical and functional properties typical of the abnormal alpha 2-antiplasmin Enschede. The naturally occurring mutant may serve as a model for investigating the structures that determine the properties of an inhibitor versus those of a substrate in serine protease inhibitors. 相似文献
7.
Structure of complex of synthetic HIV-1 protease with a substrate-based inhibitor at 2.3 A resolution 总被引：22，自引：0，他引：22
M Miller J Schneider B K Sathyanarayana M V Toth G R Marshall L Clawson L Selk S B Kent A Wlodawer 《Science (New York, N.Y.)》1989,246(4934):1149-1152
The structure of a complex between a peptide inhibitor with the sequence N-acetyl-Thr-Ile-Nle-psi[CH2-NH]-Nle-Gln-Arg.amide (Nle, norleucine) with chemically synthesized HIV-1 (human immunodeficiency virus 1) protease was determined at 2.3 A resolution (R factor of 0.176). Despite the symmetric nature of the unliganded enzyme, the asymmetric inhibitor lies in a single orientation and makes extensive interactions at the interface between the two subunits of the homodimeric protein. Compared with the unliganded enzyme, the protein molecule underwent substantial changes, particularly in an extended region corresponding to the "flaps" (residues 35 to 57 in each chain), where backbone movements as large as 7 A are observed. 相似文献
8.
9.
锌胁迫对银中杨生长发育和化学防御的影响 总被引：2，自引：0，他引：2
10.
旨在研究不同抑制剂和激活剂对梨星毛虫Illiberis pruni中肠蛋白酶活性的影响。利用生化技术分别测定梨星毛虫幼虫不同龄期的4种中肠蛋白酶（总蛋白酶、强碱性胰蛋白酶、弱碱性胰蛋白酶和胰凝乳蛋白酶）活性,进而在最适龄期（4龄幼虫）测定蛋白酶激活剂（EDTA,MgCl2,EGTA,CaCl2）和抑制剂（PMSF,TPCK,STI,TLCK,IAA,DTT）对梨星毛虫中肠蛋白酶活性的影响。结果表明：梨星毛虫幼虫中肠总蛋白酶、强碱性胰蛋白酶、弱碱性胰蛋白酶、胰凝乳蛋白酶均在4龄具有最高酶活性。所有试剂均对总蛋白酶有激活作用;5 mmol/L CaCl2对强碱性胰蛋白酶抑制作用最高;对弱碱性胰蛋白酶有抑制作用的仅有5 mmol/L DTT;对胰凝乳蛋白酶抑制效果最佳的为10 mmol/L EGTA。所筛选的对梨星毛虫主要中肠蛋白酶具有抑制作用的抑制剂,对以昆虫中肠蛋白酶为靶标的绿色害虫防控技术的开发具有参考价值。 相似文献
11.
Effects of inhibitors on the protease profiles and degradation of activated Cry toxins in larval midgut juices of Cnaphalocrocis medinalis(Lepidoptera: Pyralidae) 
下载免费PDF全文
下载免费PDF全文 Midgut juice plays an important role in food digestion and detoxification in insects. In order to understand the potential of midgut juice of Cnaphalocrocis medinalis(Guenée) to degrade Bt proteins, the enzymatic activity of midgut juice and its degradation of Bt proteins(Cry2 A, Cry1 C, Cry1 Aa, and Cry1 Ac) were evaluated in this study through protease inhibitor treatments. The activities of total protease in midgut juices were significantly inhibited by phenylmethylsulfonyl fluoride(PMSF), tosyl-L-lysine chloromethyl ketone(TLCK), pepstatin A and leupeptin. The enzymatic activity of chymotrypsin was significantly inhibited by PMSF, and enzymatic activity of trypsin was significantly inhibited by ethylenediaminetetraacetic acid(EDTA), PMSF, tosyl phenylalanine chloromethyl ketone(TPCK), TLCK and trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane(E-64). EDTA could significantly inhibit the degradation of Cry2 A by C. medinalis. EDTA, PMSF, TPCK, and TLCK could inhibit the degradation of Cry1 C and Cry1 Aa. EDTA, PMSF, TPCK, TLCK, and E-64 could inhibit the degradation of Cry1 Ac. Our results indicated that some protease inhibitors hindered various enzymatic activities in the larval midgut of C. medinalis, which may reduce the insect's ability to degrade Bt toxins. These findings may aid the application of protease inhibitors in the management of this insect pest in the future. 相似文献
12.
分子标记辅助选择改良杂交水稻的白叶枯病抗性 总被引：16，自引：0，他引：16
分子标记辅助选择技术以其对目标基因快速而精确的选择为回交育种提供了非常有效的工具。华中农业大学作物遗传改良实验室运用分子标记辅助的回交育种方法,将广谱高抗白叶枯病基因Ｚａ２１迅速导入到杂交水稻的两个优良恢复系明灰６３和６０７８之中,成功地完成了其抗生改良,并通过配组而达到了改良杂交水稻抗性的目的。本研究所运用的分子标记辅助的水稻回交育种程序是：通过一次杂交、二次回交改良杂交水稻抗性的目的。本研究所 相似文献
13.
Conserved folding in retroviral proteases: crystal structure of a synthetic HIV-1 protease 总被引：57，自引：0，他引：57
A Wlodawer M Miller M Jaskólski B K Sathyanarayana E Baldwin I T Weber L M Selk L Clawson J Schneider S B Kent 《Science (New York, N.Y.)》1989,245(4918):616-621
The rational design of drugs that can inhibit the action of viral proteases depends on obtaining accurate structures of these enzymes. The crystal structure of chemically synthesized HIV-1 protease has been determined at 2.8 angstrom resolution (R factor of 0.184) with the use of a model based on the Rous sarcoma virus protease structure. In this enzymatically active protein, the cysteines were replaced by alpha-amino-n-butyric acid, a nongenetically coded amino acid. This structure, in which all 99 amino acids were located, differs in several important details from that reported previously by others. The interface between the identical subunits forming the active protease dimer is composed of four well-ordered beta strands from both the amino and carboxyl termini and residues 86 to 94 have a helical conformation. The observed arrangement of the dimer interface suggests possible designs for dimerization inhibitors. 相似文献
14.
[目的]草鱼卵匀浆液中纯化获得蛋白酶抑制剂。[方法]采用Sephadex凝胶层析技术和发色底物检测,经分离与纯化获得具有专一性抑制活性的蛋白酶抑制剂。在不同温度(30～100℃)和酸碱(pH 2～11)条件下研究该抑制剂稳定性。[结果]从草鱼卵中分离到表观分子量50 kD的蛋白酶抑制剂,其对胰蛋白酶的最低抑制浓度约为500μg/ml,抑制常数为14.6 nmol/L。该蛋白酶抑制剂还具有高度的热稳定和酸碱稳定性。[结论]该研究可为淡水鱼卵的高效利用提供理论依据。 相似文献
15.
Design, activity, and 2.8 A crystal structure of a C2 symmetric inhibitor complexed to HIV-1 protease 总被引：22，自引：0，他引：22
J Erickson D J Neidhart J VanDrie D J Kempf X C Wang D W Norbeck J J Plattner J W Rittenhouse M Turon N Wideburg 《Science (New York, N.Y.)》1990,249(4968):527-533
A two-fold (C2) symmetric inhibitor of the protease of human immunodeficiency virus type-1 (HIV-1) has been designed on the basis of the three-dimensional symmetry of the enzyme active site. The symmetric molecule inhibited both protease activity and acute HIV-1 infection in vitro, was at least 10,000-fold more potent against HIV-1 protease than against related enzymes, and appeared to be stable to degradative enzymes. The 2.8 angstrom crystal structure of the inhibitor-enzyme complex demonstrated that the inhibitor binds to the enzyme in a highly symmetric fashion. 相似文献
16.
17.
Ninety one isolates of Xanthomonas oryzae pv. Oryzae were collected from different rice growing regions in China and determined for their virulence on 24 rice near-isogenic lines containing single resistance gene and 2-4 genes:IRBB1 (Xa1),IRBB2 (Xa2),IRBB3 (Xa3), IRBB4 (Xa4), IRBB5 (xa5), IRBB7 (Xa7), IRBB8 (xa8), IRBB10 (Xa10), IRBB11 (Xa11),IRBB13 (xa13),IRBB14 (Xa14), IRBB21 (Xa21), IR24 (Xa18), IRBB50 (Xa4 + xa5), IRBB51 (Xa4 + xa13), IRBB52 (Xa4 + Xa21), IRBB53 (xa5 + xa13), IRBB54 (xa5 + Xa21), IRBB55 (xa13 + Xa21),IRBB56 (Xa4 + xa5 + xa13), IRBB57 (Xa4 + xa5 + Xa21), IRBB58 (Xa4 + xa13 + Xa21),IRBB59 (xa5 + xa13 + Xa21) and IRBB60 (Xa4 + xa5 + xa13 + Xa21). The results showed that most isolates were less virulent on lines with more than one genes pyramided than those
with single resistance gene. The isolates tested were more virulent on IR24 and IRBB10,less virulent on IRBB5, IRBB7 and IRBB21. Based on interactions between isolates and rice near-isogenic lines, 7 cultivars with single gene (IRBB5, IRBB4, IRBB3, IRBB14, IRBB2,
IRBB1 and IR24) were chosen as the differentials, and the tested isolates were classified into 7 virulence groups. The reaction patterns of the 7 groups in order were: RRRRRRR,RRRRRRS, RRRRRSS, RR/SRRSSS, RRRSSSS, RRSSSSS, RSSSSSS. The virulence frequencies were 7.69, 6.59, 14.29, 12.09, 14.29, 28.57 and 16.48％ respectively. The elementary system for races identification has been established in China based on the results. It will be possible to compare with races in other countries, and the results will facilitate the evelopment of rice resistance breeding to bacterial blight in China. 相似文献
18.
Hong L Koelsch G Lin X Wu S Terzyan S Ghosh AK Zhang XC Tang J 《Science (New York, N.Y.)》2000,290(5489):150-153
Memapsin 2 (beta-secretase) is a membrane-associated aspartic protease involved in the production of beta-amyloid peptide in Alzheimer's disease and is a major target for drug design. We determined the crystal structure of the protease domain of human memapsin 2 complexed to an eight-residue inhibitor at 1.9 angstrom resolution. The active site of memapsin 2 is more open and less hydrophobic than that of other human aspartic proteases. The subsite locations from S4 to S2' are well defined. A kink of the inhibitor chain at P2' and the change of chain direction of P3' and P4' may be mimicked to provide inhibitor selectivity. 相似文献
19.
为探讨茉莉酸甲酯( MeJA)诱导巨桉幼苗防御反应的生化机制及其对桉树枝瘿姬小蜂的抗性效应,在室内采用喷施不同浓度MeJA处理,测定并分析了MeJA对桉叶苯丙氨酸解氨酶( PAL)、超氧化物歧化酶( SOD)、过氧化物酶( POD)和多酚氧化酶(PPO)4种防御酶活性,以及胰蛋白酶抑制剂(TI)和胰凝乳蛋白酶抑制剂(CI)2种植物蛋白酶抑制剂活性的影响。结果表明,喷施MeJA处理24-148 h后,巨桉幼苗叶片PAL、 SOD、 POD和PPO 四种防御酶和TI、 CI两种蛋白酶抑制剂活性均有不同程度的变化;用1.00 mmol·L-1 MeJA处理后桉树枝瘿姬小蜂种群趋势指数为24.13,防治效果达70.98%。 MeJA处理可诱导巨桉幼苗产生明显的防御反应,相关防御酶活性的变化与MeJA浓度和处理时间有关; MeJA可诱导巨桉幼苗产生抗虫性,对桉树枝瘿姬小蜂繁殖力和种群趋势指数产生影响,具有明显的防治效果。 相似文献
20.
戴秋秋 《金陵科技学院学报》2007,23(1):38-41
铬酸盐及其复合配方作为第一代缓蚀剂，因在工业循环水中的缓蚀效率显著，被推为缓蚀剂之首。随着有害Cr^6＋离子的排放受到限制，开发新一代的钼酸盐缓蚀剂就日益引起人们的重视。通过从钼系缓蚀剂抑制腐蚀的环境因素出发，综述了钼系缓蚀剂的进展，并阐明了钼膦系缓蚀剂具有明显的缓蚀协同效应。 相似文献