Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heparin cofactor, a thrombin inhibitor, is purified from human plasma by affinity chromatography on heparin-agarose. The nature of the binding between thrombin and the inhibitor is studied by treatment of the complex with 6 M guanidinium chloride, hydroxylamine, and dilute alkali. The complex is not dissociated during gel chromatography in 6 M guanidinium chloride. This result supports an earlier proposal that formation of the complex includes the formation of a covalent bond. Treatment of dodecyl sulfate-denatured complex with hydroxylamine results in dissociation of the complex to yield free thrombin and heparin cofactor. Hydroxylamine does not dissociate the complex unless it is denatured. The complex is also dissociated in dilute sodium hydroxide (pH 12) solutions. These results indicate that the covalent bond between thrombin and the inhibitor is a carboxylic ester.
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PMID:Evidence for an ester bond between thrombin and heparin cofactor. 6 Jul 92

Protease-like activity which split plasminogen-free fibrin was demonstrated in 2 M KSCN extracts of the lung and spleen of conventional rats. The activity was virtually undetectable in tissue extracts from germ-free rats. The extracts from the conventional rat tissues split fibrin and fibrinogen remarkably at neutral pH, but not casein, when examined using fibrin, fibrinogen-agar and casein-agar plates. The fibrinolytic activity was inhibited by STI and DFP, indicating a serine protease nature. The activity was not inhibited by TLCK, t-AMCHA or dansyl-L-arginine-methylpiperidine amide (a selective synthetic thrombin inhibitor, OM189). It was neither activated nor inhibited by cysteine, KCN or iodoacetic acid. The results obtained indicate that the protease-like activity of the lung and spleen extracted with 2 M KSCN from conventional rats has properties which differ from those of trypsin, plasmin, plasminogen-activator, thrombin, and cathepsin A, B and C.
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PMID:Fibrinolytic activity of lung and spleen extracts observed in conventional but not in germ-free rats. 9 68

Purified human prothrombin was activated, both in the absence and in the presence of thrombin inhibitors (diisopropylfluorophosphate or hirudin), by a coagulant principle isolated from Dispholidus typus venom. The process of activation was monitored by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In the absence of thrombin inhibitor, prolonged incubation of prothrombin with the purified venom yielded thrombin, fragment 1 (F 1) and fragment 2 (F 2). In the presence of diisopropylfluorophosphate, which in the experimental conditions used inhibited only partially the thrombin generated activity, products obtained upon activation of prothrombin by venom were F 1 and a two-chain, disulfide-bridged protein of 58 000 daltons called meizothrombin (des F 1). In the presence of hirudin, which fully inhibited thrombin generated activity, prothrombin activation by the venom did not liberate any fragment, but prothrombin was converted to a derivative composed of two disulfide-bridged polypeptide chains of 48 000 and 37 000 daltons, called meizothrombin. These results are similar to those reported by others when studying the process of prothrombin activation by Echis carinatus venom and allow to conclude that Dispholidus typus venom cleaves a bond linking the A and B chains of thrombin, converting prothrombin into meizothrombin. This enzyme is then responsible for the cleavage of the bond linking F 1 and F 2 and the bond linking F2 the A chain of thrombin.
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PMID:The mechanism of activation of human prothrombin by an activator isolated from Dispholidus typus venom. 10 63

Acylation of bovine prothrombin by cytraconic anhydride results in the formation of the thrombin active site, which provides the degradation of highly specific thrombin substrate, N-bensoyl-Phe-Val-Arg p-nitroanilide. This reaction is inhibited with hirudin, highly specific thrombin inhibitor.
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PMID:[Use of N-benzoyl-phenylalanyl-valyl-arginine p-nitroanilide and hirudin for the detection of enzymatic activity under prothrombin acylation by citraconic anhydride]. 56 96

A number of novel aromatic Tris-amidines have been synthesized and investigated for their antiproteolytic property. The basic structure of the compounds is that of mesitylene where each of the methyl groups has been substituted with a 3- or 4-amidinophenoxy moiety. The compounds displayed considerable activity against trypsin (EC 3.4.21.4) and thrombin (EC 3.4.21.5), but proved most effective against porcine pancreatic kallikrein (EC 3.4.21.8). With this enzyme a Ki value of 2.43-10(-8) M was recorded for alpha,alpha',alpha''-tris(4-amidino-2-bromophenoxy)mesitylene at pH 8.1 and 37 degrees C. The most potent thrombin inhibitor, alpha,alpha',alpha''-tris(3-amidinophenoxy)mesitylene, had a Ki value of 6.51-10(-7) M and was also a strong overall anticoagulant. The inhibitors were able to interfere with the kinin release by human plasma kallikrein at concentrations as low as 1-10(-10) M. However, despite this remarkable antikallikrein effect and the known importance of plasma kallikrein in the activation of Hageman factor (factor XII), the compounds had only little influence on the early stages of blood coagulation.
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PMID:Aromatic Tris-amidines. A new class of highly active inhibitors of trypsin-like proteases. 108 99

Heparin cofactor, a thrombin inhibitor, is purified from human plasma by affinity chromatography on heparin-agarose. The nature of the binding between thrombin and the inhibitor is studied by treatment of the complex with 6 M guanidinium chloride, hydroxylamine, and dilute alkali. The complex is not dissociated during gel chromatography in 6 M guanidinium chloride. This result supports an earlier proposal that formation of the complex includes the formation of a covalend bond. Treatment of dodecylsulfate-denatured complex with hydroxylamine results in dissociation of the complex to yield free thrombin and heparin cofactor. The complex is also dissociated in dilute NaOH (pH 12) solutions. These results indicate that the covalent bond between thrombin and the inhibitor is a carboxylic ester.
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PMID:Evidence for the formation of an ester between thrombin and heparin cofactor. 118 Sep 62

The present study investigated whether or not thrombin may affect the induction of nitric oxide (NO) synthase caused by interleukin-1 beta in cultured smooth muscle cells (SMCs) from the rat aorta. The release of nitrite, an oxidation product of NO, from interleukin-1 beta-activated SMCs was inhibited by thrombin. The inhibitory effect of thrombin was prevented by hirudin, a thrombin inhibitor, and required the presence of thrombin during the induction period. Under bioassay conditions, the perfusate from interleukin-1 beta-activated SMCs relaxed endothelium-denuded rat aortic rings precontracted with phenylephrine. The perfusate from untreated SMCs or cells exposed to thrombin alone or to interleukin-1 beta in combination with thrombin relaxed only minimally the detector blood vessel. These observations demonstrate that thrombin inhibits the production of NO by the inducible NO synthase in cultured vascular SMCs.
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PMID:The inducible nitric oxide synthase is impaired by thrombin in vascular smooth muscle cells. 128 51

The jawed leech, Hirudinaria manillensis is closely related to Hirudo medicinalis, both belonging to the same family Arhynchobdellida. From Hirudo, two potent peptide inhibitors, hirudin (a thrombin inhibitor) and eglin (an elastase/chymotrypsin inhibitor) have been characterised in detail. During our studies to isolate thrombin inhibitor from the leech Hirudinaria a potent inhibitor, analogous to eglin, was also detected. Results indicate that this inhibitor, which we have named 'GELIN', is significantly different from eglin. Gelin was isolated and purified to homogeneity by ion exchange chromatography and reverse phase HPLC. The isoelectric point of Gelin was estimated to be 4.55, in contrast to 6.45 for eglin. The molecular weight of Gelin was similar to eglin, as estimated by SDS-PAGE. Amino-terminal sequence analysis of the first 29 residues show no sequence homology with eglin or any other serine protease inhibitors. Circular dichroism studies showed that the secondary structure of Gelin has no helix, 58% beta sheets and 42% random structures compared to 19% helix, 56% beta sheets and 25% random structures in eglin. Like eglin, Gelin inhibits elastase, cathepsin G and chymotrypsin but has little or no activity towards plasmin, thrombin, pepsin and trypsin. These data suggest that the elastase inhibitors from these two species of leech are fundamentally different in structure, indicative of independent evolutionary origin.
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PMID:Biochemical characterisation of a pancreatic elastase inhibitor from the leech Hirudinaria manillensis. 128 66

Hirudin is a potent and specific thrombin inhibitor: compared with heparin thrombin inhibition occurs directly and does not require the presence of plasma cofactors. Recombinant hirudin is well tolerated in animals and in healthy volunteers. Its clearance half-life after IV administration range from 1 to 2 hours and its bioavailability after subcutaneous administration reaches 75%. In most of the experimental models the ratio of the haemorrhagic side effect against the antithrombotic efficacy is satisfactory. Hirudin analogs are mono or bivalent according to their recognition site on thrombin. Bivalent derivatives (Hirulogs) have been mostly evaluated: they exhibit pharmacologic properties similar experimental to that of recombinant hirudin and have been successfully used in several thrombosis models and in healthy volunteers. Taking into account these data the most appropriate use for hirudin and hirudin derivatives should be clinical situations where the role of thrombin is important or which are only partially controlled by heparin therapy.
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PMID:[Hirudin and hirudin fragments]. 129 82

We asked the question, "Can thalassemic erythrocytes play some role in alteration of the hemostatic system?", because clinical examination of thalassemic patients shows symptoms and signs related to alterations in hemostatic and circulatory systems, and thalassemic erythrocytes are different from normal erythrocytes. We obtained one of the answers to the question: The erythrocytes of postsplenectomized patients of beta-thalassemia/HbE disease could stimulate their own platelets to aggregate spontaneously. To know the role of erythrocytes in platelet aggregation, we wanted to examine the effect of thalassemic erythrocytes on the coagulation system by focusing of PF3-like activity of erythrocytes, because PF3-like activity of the ghosts of erythrocytes had been reported. For the study, we tried to develop a technique that was accurate and sensitive enough to detect PF3-like activity of blood. The system we developed was the following: 1) We activated the intrinsic coagulation pathway of commercial standard plasma by ellagic acid. 2) CaCl2, a fixed amount of PF 3 and synthetic thrombin inhibitor MD 805 were added to the reaction mixture. 3) At a fixed time, thrombin activity in the mixture was measured by using S-2238 as a substrate. At full activation of the contact system by ellagic acid, the amount of thrombin formed in a certain time depended on the amount of PF3-like substances such as cephalin, freeze-thawed platelets or ghosts of erythrocytes added to the test system, indicating that PF3-like activity of those substances can be measured by the activity of thrombin generated in a fixed time.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Development of a new method for detection of platelet factor 3 like activity. 129 93


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