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:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombolytic therapy paradoxically induces the formation of fibrinopeptide A, fibrin degradation products and thrombin-antithrombin complexes, indicating thrombin generation. Part of the mechanism of this thrombin generation under the influence of thrombolytic agents was unraveled in this study. We measured thrombin with a chromogenic substrate at several time intervals after recalcification of citrated plasma which had been preincubated with urokinase, streptokinase, recombinant tissue plasminogen activator (rt-PA) or recombinant single-chain urokinase-type plasminogen activator (rscu-PA). Thrombin generation induced by the addition of thromboplastin together with calcium (extrinsic pathway) was greatly accelerated in the presence of streptokinase (from about 7 to 2 min), and to a lesser extent in the presence of urokinase, rt-PA or rscu-PA. Similar effects were seen after the addition of calcium to the plasma containing the thrombolytic agent and preincubated with partial thromboplastin (intrinsic pathway). Hirudin quenched the conversion of the chromogenic substrate completely, confirming that thrombin was the active enzyme. Aprotinine did not affect the results, and the effect of streptokinase was also observed in plasminogen-depleted plasma. We conclude that streptokinase, and to a lesser extent other thrombolytic agents, activate the prothrombinase complex directly or indirectly through a calcium-dependent mechanism, independently of plasminogen, with a resulting acceleration of thrombin generation.
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PMID:Thrombin generation induced by the intrinsic or extrinsic coagulation pathway is accelerated by streptokinase, independently of plasminogen. 816 24

The effect of blood access on platelets and clotting factors was investigated in 46 azotemic patients. Arteriovenous fistula was used in 10 patients (AVF group), and polyurethane double-lumen catheters were inserted through the subclavian vein in 6 patients (PUS group) or through the femoral vein in 15 patients (PUF group). Indwelling urokinase-immobilized single-lumen catheters and double-lumen catheters were placed in the femoral vein of 5 patients (UKS group) and 10 patients (UKD group), respectively. Blood cell counts, beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), prothrombin time, and activated partial thromboplastin time were measured before insertion while catheters were indwelling and after catheters were pulled out. Although the platelet count decreased to 83% of the initial value during indwelling in the PUF group and 89% in the PUS group, it did not decrease in the AVF, UKS, and UKD groups. There were no differences between the PUF and PUS groups nor between the UKS and UKD groups. Plasma beta-TG increased in the PUF and UKD groups with indwelling catheters but did not change with the AVF. From these results, we conclude that the AVF did not activate platelets, the urokinase-immobilized catheter activated platelets, and the polyurethane catheter activated and decreased platelets. This might be due to the different surface properties of each blood access. Thus, the urokinase-immobilized catheter seems to be more favorable than the polyurethane catheter for emergency blood access.
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PMID:Effect of blood access on the platelets of azotemic patients initiating dialysis therapy. 821 44

Pharmacokinetics of two doses of the recombinant single-chain urokinase-type plasminogen activator (r-scu-PA) saruplase (40 and 20 mg) and its effect on fibrinolytic and haemostatic parameters were studied in six healthy male subjects using a randomized, double-blind, placebo-controlled, cross-over study. Special precautions were taken to prevent artefactual in vitro effects on fibrinolytic activity. The clearance of saruplase ranged from 310 to 862 ml/min and the apparent volume of distribution of the central compartment was about 8 1. Both doses of saruplase caused alpha 2-antiplasmin consumption, indicating some systemic fibrinolytic activation. However, the 20 mg dose caused no detectable fibrinogen breakdown and only a small increase in total fibrin/fibrinogen degradation products (TDP) (from 0.16 microgram/ml [range 0.14 to 0.19] to 0.78 microgram/ml [range 0.56 to 1.26]), while the 40 mg dose produce a fibrinogen breakdown to an average value of 44% (range 19 to 60%) and TDP increased from 0.12 microgram/ml (range 0.11-0.12) to 2.29 micrograms/ml (range 0.45 to 5.55). The breakdown of fibrinogen was related to the quantity of saruplase converted to active two-chain u-PA (tcu-PA) in vivo (6 to 22% conversion). There were no important effects of saruplase on overall blood coagulation (activated partial thromboplastin time) and platelet function (collagen induced platelet aggregation, urinary [2,3-dinor]-thromboxane B2 excretion and plasminogen activator inhibitor 1 [PAI-1] release from platelets). Saruplase is cleared rapidly from the plasma and a variable amount is converted to tcu-PA. This two-chain form of u-PA probably causes the dose-dependent systemic fibrinolytic activation.
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PMID:Pharmacokinetics of saruplase, a recombinant unglycosylated human single-chain urokinase-type plasminogen activator and its effects on fibrinolytic and haemostatic parameters in healthy male subjects. 823 42

A Limulus intracellular coagulation inhibitor, designated LICI, was isolated from hemocytes of the Japanese horseshoe crab (Tachypleus tridentatus), using three steps of chromatography, including dextran sulfate-Sepharose CL-6B, Sephacryl S-200, and Mono S. LICI is a single-chain glycoprotein with an apparent M(r) = 48,000 estimated by SDS-polyacrylamide gel electrophoresis. It blocks the amidolytic activities of Limulus lipopolysaccharide-sensitive serine protease, factor C, by forming a covalent 1:1 complex with the protease. The second-order rate constant for inhibition of factor C was 2.5 x 10(6) M-1 s-1 at 37 degrees C. LICI also inhibited human alpha-thrombin, rat salivary kallikrein, bovine plasmin, and trypsin but not Limulus clotting enzyme, Limulus factor B, bovine factor Xa, human factor XIa, human tissue plasminogen activator, human urokinase, chymotrypsin, elastase, and papain. Glycosaminoglycans such as heparin and heparan sulfate had no effect on the inhibitory activity. A cDNA coding for LICI was isolated from a hemocyte cDNA library. The open reading frame of the 1,257-base pair cDNA codes for the mature protein of 394 amino acids, of which 223 residues were confirmed by amino acid sequence analysis. LICI shows significant sequence identities to members of the serpin superfamily, such as human plasminogen activator inhibitor type 2 (40%) and human monocyte/neutrophil elastase inhibitor (39%). LICI contains a putative reactive site, -Arg-Ser-, at the corresponding position present in several inhibitors of the serpin superfamily. The subcellular localization, determined using an anti-LICI polyclonal antibody, indicated that LICI colocates with the Limulus serine protease zymogens in large granules in the hemocyte.
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PMID:A Limulus intracellular coagulation inhibitor with characteristics of the serpin superfamily. Purification, characterization, and cDNA cloning. 827 48

A 37-year-old woman with increasing dyspnoea over several months suddenly developed severe ortho- and tachypnoea as well as cyanosis of the lips and acrocyanosis. Pulmonary angiography revealed massive bilateral pulmonary emboli with a systolic pulmonary artery pressure of 75 mm Hg. Phlebography demonstrated a thrombotic occlusion of the deep veins of the left leg extending to the distal femoral vein. Thrombolysis treatment was started via an indwelling pulmonary artery catheter (500,000 IU urokinase and 10,000 IU heparin as bolus, then 1 mill. IU urokinase and 1,000 IU heparin per hour). After two hours an incomplete left-sided paresis occurred (involving ocular and facial muscles, dysarthria, left arm and left leg) and the thrombolytic infusion was stopped. But cerebral computed tomography (CT) did not demonstrate any intracerebral haemorrhage. The heparin infusion was restarted (partial thromboplastin time between 70 and 90 s). CT examinations during the next few days showed the development of an ischaemic infarction in the distribution of the right medial cerebral artery. Angiography demonstrated occlusion of the right internal carotid artery. The diagnosis of a paradoxical embolus was supported by easy cardiac catheter passage through a patent foramen ovale. Subsequent pulmonary angiography demonstrated a thrombus-free pulmonary arterial circulation with a normal pulmonary arterial pressure. There was gradual and extensive regression of the incomplete hemiparesis.
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PMID:[Paradoxical cerebral embolism during fibrinolysis therapy in deep vein thrombosis and pulmonary embolism]. 820 47

The use of first generation plasminogen activators, urokinase, streptokinase and tissue plasminogen activator has revolutionized thrombolytic therapy for myocardial infarction and ischaemia, and potentially stroke. However, thrombolytic therapy employing these activators is limited by reocclusion of the very arteries being opened, which follows in a small but significant number of patients. The development of second generation plasminogen activators, e.g. staphylokinase and anisoylated plasminogen streptokinase activator complex, has not alleviated the problems encountered with classical plasminogen activators. It is now widely recognized that aberrant platelet aggregation induced primarily by thrombin, rather than plasmin, is one of the major causes of recurrent thrombosis following pharmacologic thrombolysis. Agents that (a) inhibit enzymatic and/or coagulant activity of thrombin, (b) block binding of thrombin to its receptor, and (c) interfere with the generation of thrombin by the prothrombinase complex may compromise haemostasis resulting in haemorrhage. We recently demonstrated that thrombin-induced platelet aggregation is accompanied by cleavage of aggregin, a putative ADP-receptor on the platelet surface, and that these events are indirectly mediated by intracellularly activated calpain expressed on the surface. In this review, we discuss the known mechanisms of thrombin-induced platelet aggregation and suggest relative advantages of potential pharmacological agents, being developed in our laboratory, over those that have been previously developed and tested. These inhibitors selectively prevent aggregation of platelets induced by thrombin by inhibiting calpain expressed on the surface. Moreover, one of these inhibitors which blocks thrombin-induced platelet aggregation does not interfere with other platelet responses mediated by thrombin or platelet aggregation induced by other agonists, such as, ADP, collagen, phorbol myristate acetate and thromboxane A2 mimetics. This selectivity could reduce the chances of perturbing the formation of a haemostatic plug.
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PMID:Reocclusion after thrombolytic therapy: strategies for inhibiting thrombin-induced platelet aggregation. 832 74

Both human and bovine prothrombin fragment 2 (the second kringle) have been cocrystallized separately with human PPACK (D-Phe-Pro-Arg)-thrombin, and the structures of these noncovalent complexes have been determined and refined (R = 0.155 and 0.157, respectively) at 3.3-A resolution using X-ray crystallographic methods. The kringles interact with thrombin at a site that has previously been proposed to be the heparin binding region. The latter is a highly electropositive surface near the C-terminal helix of thrombin abundant in arginine and lysine residues. These form salt bridges with acidic side chains of kringle 2. Somewhat unexpectedly, the negative groups of the kringle correspond to an enlarged anionic center of the lysine binding site of lysine binding kringles such as plasminogens K1 and K4 and TPA K2. The anionic motif is DGDEE in prothrombin kringle 2. The corresponding cationic center of the lysine binding site region has an unfavorable Arg70Asp substitution, but Lys35 is conserved. However, the folding of fragment 2 is different from that of prothrombin kringle 1 and other kringles: the second outer loop possesses a distorted two-turn helix, and the hairpin beta-turn of the second inner loop pivots at Val64 and Asp70 by 60 degrees. Lys35 is located on a turn of the helix, which causes it to project into solvent space in the fragment 2-thrombin complex, thereby devastating any vestige of the cationic center of the lysine binding site. Since fragment 2 has not been reported to bind lysine, it most likely has a different inherent folding conformation for the second outer loop, as has also been observed to be the case with TPA K2 and the urokinase kringle. The movement of the Val64-Asp70 beta-turn is most likely a conformational change accompanying complexation, which reveals a new heretofore unsuspected flexibility in kringles. The fragment 2-thrombin complex is only the second cassette module-catalytic domain structure to be determined for a multidomain blood protein and only the third domain-domain interaction to be described among such proteins, the others being factor Xa without a Gla domain and Ca2+ prothrombin fragment 1 with a Gla domain and a kringle.
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PMID:Structures of the noncovalent complexes of human and bovine prothrombin fragment 2 with human PPACK-thrombin. 838 13

A recent report described a thrombin inhibitory activity in the soluble fraction of human placenta and the cytosolic fraction of K562 cells. Isolation and characterization of the functionally inactive 35-38-kDa placental form of this protein revealed that it was a novel serine proteinase inhibitor (Coughlin, P. B., Tetaz, T., and Salem, H. H. (1993) J. Biol. Chem. 268, 9541-9547). In the present study, we observed a 67-kDa sodium dodecyl sulfate (SDS)-stable complex when 125I-thrombin was incubated with the cytosolic fraction of a monkey kidney epithelial cell line, BSC-1. This complex was not observed in either the particulate cell fraction extracted with 0.2% Triton X-100 or medium conditioned by cells, suggesting that the thrombin-complexing factor is confined to the cytoplasm. The cytoplasmic antithrombin activity was purified to apparent homogeneity from the cytosol of BSC-1 cells previously pulsed with [35S]methionine by a combination of heparin-agarose chromatography, Mono Q fast protein liquid chromatography, and anhydrotrypsin-Affi-Gel 10 affinity chromatography. Analysis of the affinity-purified preparation by SDS-polyacrylamide gel electrophoresis and fluorography revealed a single protein with an apparent molecular mass of 38 kDa. The purified 38-kDa protein inhibited the amidolytic activities of thrombin, trypsin, urokinase, and factor Xa but not that of elastase. Incubation of the 38-kDa protein with excess thrombin identified approximately 60% of the labeled 38-kDa protein in an SDS-stable 67-kDa complex. The purified 38-kDa inhibitor was cleaved with cyanogen bromide and the isolated peptides subjected to microsequencing. Amino acid sequence obtained for a region within this protein exhibited significant homology with human antithrombin III and plasminogen activator inhibitors 1 and 2. This homologous peptide contained the full complement of residues designated as highly conserved in helix F of the greater serine proteinase inhibitor superfamily. In addition, an internal sequence of GGGGDIHQGF was found in the monkey cytoplasmic inhibitor, which is identical to that reported for an internal sequence of the human placental inhibitor. These findings confirm the existence of a novel cytoplasmic serine proteinase inhibitor in mammalian cells and provide additional details of its molecular properties. The physiological function of this novel serine proteinase inhibitor in cytoplasm is unknown.
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PMID:Isolation and characterization of an intracellular serine proteinase inhibitor from a monkey kidney epithelial cell line. 840 7

The myxoma and malignant rabbit fibroma poxviruses are lethal tumorigenic viruses of rabbits whose virulence is modulated by the production of a virus-encoded secreted serine proteinase inhibitor, SERP-1. This viral protein was detected in medium harvested from myxoma and malignant rabbit fibroma virus-infected cells, and its inhibitory profile has been characterized by gel and kinetic analysis. SERP-1 forms complexes with and inhibits the human fibrinolytic enzymes plasmin, urokinase, and two-chain tissue-type plasminogen activator (association rate constants 3.4 x 10(4), 4.3 x 10(4), and 3.6 x 10(4) M-1 s-1 respectively). It is also able to inhibit C1S, the first enzyme in the complement cascade with an association rate constant which was unaffected by the addition of heparin (1.3 x 10(3) M-1 s-1). SERP-1 acts as a substrate for and is cleaved by thrombin, porcine trypsin, human neutrophil elastase, porcine pancreatic elastase, thermolysin, subtilisin, bovine alpha-chymotrypsin, and factor Xa. Incubation with kallikrein and cathepsin G had no effect. The structure of SERP-1 has been modeled on other members of the serpin family which revealed the characteristic serpin architecture apart from the absence of the D-helix. Structural analysis and kinetic assays demonstrate that the absence of this region does not prevent inhibitory activity and furthermore allow the identification of cysteine residues involved in internal and intermolecular disulfide bonding.
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PMID:Inhibition of plasmin, urokinase, tissue plasminogen activator, and C1S by a myxoma virus serine proteinase inhibitor. 841 56

The local infusion of urokinase may be complicated by hemorrhage. Except for maintaining fibrinogen levels above 100 mg/dL, no other criteria exist for titrating the dose of urokinase to avoid hemorrhagic complications. A retrospective examination of the fibrinolytic and coagulation states was performed on 11 patients receiving local high-dose urokinase (240,000 U/hr) and heparin for thrombolysis of acute occlusions to identify parameters other than fibrinogen levels that may correlate with bleeding complications. Five patients experienced bleeding complications, 3 of whom had partial thromboplastin time (PTT) values greater than 150 seconds. None of the five patients having hemorrhagic complications had fibrinogen levels below 100 mg/dL at any time. Urokinase began to enhance the effect of heparin on PTT values as a result of reducing fibrinogen levels. In 10 of 11 patients this effect caused PTT values to at least double when compared with heparin alone. This substantial rise in PTT occurred only after fibrinogen levels approached 200 mg/dL in 8 of 11 patients. Although the number of patients is small, these data suggest that when heparin is used during thrombolysis, closer PTT monitoring should be carried out as fibrinogen levels begin to decline, especially when they approach 200 mg/dL, to avoid excessive PTT elevations and subsequent bleeding.
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PMID:Combined effects of urokinase and heparin on PTT values during thrombolytic therapy. 843 4


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