Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Lys binding site of kringle 1 and 4 (K1 and K4) of plasminogen (PG) has been modeled on the basis of the three-dimensional structure of kringle 1 of prothrombin and 300- and 600-MHZ proton nuclear magnetic resonance observations. These structures were then compared to the corresponding regions of modeled kringle 1 and 2 of tissue plasminogen activator (PA). The coordinates of the modeled structures have been refined by energy minimization in the presence and absence of epsilon-aminocaproic acid ligand in order basically to remove unacceptable van der Waals contacts. The binding site is characterized by an apparent dipolar surface, the polar parts of which are separated by a hydrophobic region of highly conserved aromatic residues. Zwitterionic ligands such as Lys and epsilon-aminocaproic acid form ion pair interactions with Asp55 and Asp57 located on the dipolar surface; the latter are also conserved in all the Lys binding kringles. The cationic center of the dipolar surface is Arg71, in the case of PGK4, and is composed of Arg34 and Arg71 in PGK1. The doubly charged anionic/cationic interaction centers of the latter might account for the larger binding constants of PGK1 for like-ligands but the modeling suggests that PGK4 might be kinetically faster in binding bulkier ligands. The binding site region of PAK2, which also binds Lys, resembles those of PGK1 and PGK4. Since PAK2 lacks both cationic center Arg residues, ligand carboxylate binding appears to be accomplished though an imidazolium ion of His64, which is located just below the outer surface of the kringle.
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PMID:Lysine/fibrin binding sites of kringles modeled after the structure of kringle 1 of prothrombin. 313 47

We have previously reported paradoxical prothrombotic effects manifest by elevations of fibrinopeptide A (FPA) after administration of streptokinase to patients with acute myocardial infarction. To characterize mechanisms responsible and their dependence on streptokinase (SK) as opposed to other activators of the fibrinolytic system, the present study was performed to compare effects of streptokinase, tissue-type plasminogen activator (t-PA), and urokinase on plasma and on purified prothrombin in concentrations similar to those achieved pharmacologically. The effects of plasmin were assessed to determine the extent to which the elevations of FPA seen could be attributed to activation of plasminogen. Elevations of FPA were observed after incubation of each of the activators with citrated plasma at 37 degrees C for 60 minutes. However, they were most marked with streptokinase (64.5 +/- 4.6 pmol FPA/ml (mean +/- SE) with 100 IU SK/ml, and 77.6 +/- 5.0 pmol/ml with 500 IU SK/ml). Elevations of FPA induced by streptokinase were attenuated by 100 IU/ml heparin [15.2 +/- 1.9 pmol/ml after 100 IU of SK (p less than 0.001 compared with results with streptokinase without heparin)]. Human plasmin, 2.5 CTA/ml, caused changes similar to those induced by streptokinase. The minimal elevations of FPA induced by t-PA or urokinase (less than 10 pmol/ml without heparin) were not significantly attenuated by heparin. Incubation of barium citrate adsorbed plasma (vitamin K factor depleted) with streptokinase markedly attenuated elevation of FPA. Addition of prothrombin (1.5 microM) and streptokinase (100 IU/ml) to the barium citrate adsorbed plasma elicited elevations of FPA similar to those induced by streptokinase in citrated plasma. Amidolytic activity with the "thrombin" substrate H-D-phenylalanyl-L-pipecolyl-L-arginine-p-nitroanilide dihydrochloride (S-2238) was evident when streptokinase, plasminogen (0.24 microM), and prothrombin (1.5 microM) were incubated in buffer. Thus, concentrations of streptokinase that are low in terms of therapeutic blood levels activate prothrombin in plasma, likely due to activation of plasminogen. Neither tissue-type plasminogen activator nor urokinase in pharmacologically comparable concentrations increase thrombin activity appreciably perhaps because of less intense activation of plasminogen. Consideration of the prothrombotic effects observed may be relevant to selection of specific agents for therapeutic thrombolysis, to appropriate titration of dose, and to the need for the use of heparin conjointly with particular activators of the fibrinolytic system such as streptokinase.
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PMID:Differential effects of activation of prothrombin by streptokinase compared with urokinase and tissue-type plasminogen activator (t-PA). 313 87

The two final phases in the haemostatic process, plasma coagulation with the formation of a fibrin clot, and fibrinolysis leading to the dissolution of fibrin clots, are reviewed. Coagulation may be initiated either by reactions occurring between components of the blood alone, the intrinsic pathway, or by reactions which also involve tissue components, termed the extrinsic pathway. In the diagnosis of coagulation disorders, it is convenient to divide the intrinsic pathway into three phases. In phase 1, resulting in the activation of factor (f) X, are involved f XII, XI, VIII and IX, platelet phospholipids, and calcium. In phase 2, prothrombin is converted to thrombin by f Xa in conjunction with f V, phospholipids, calcium. In phase 3, thrombin converts fibrinogen to fibrin, which is then stabilized by f XIII. Antithrombin III is the most important inhibitor. The key component in fibrinolysis is plasminogen, which under the influence of various activators is converted to plasmin. Plasmin is a serine protease and its main in vivo target is fibrin. Alpha 2-antiplasmin and a fast-acting inhibitor of tissue plasminogen activator are the most important inhibitors.
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PMID:Coagulation and fibrinolysis. 332

125I-labeled heparin cofactor II (HCII) was mixed with plasma and coagulation was initiated by addition of CaCl2, phospholipids, and kaolin or tissue factor. In the presence of 67 micrograms/ml of dermatan sulfate, radioactivity was detected in a band which corresponded to the thrombin-HCII complex (Mr = 96,000) upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. No other complexes were observed. The thrombin-HCII complex was undetectable when 5 units/ml of heparin was present or when prothrombin-deficient plasma was used. In experiments with purified proteases, HCII did not significantly inhibit coagulation factors VIIa, IXa, Xa, XIa, XIIa, kallikrein, activated protein C, plasmin, urokinase, tissue plasminogen activator, leukocyte elastase, the gamma-subunit of nerve growth factor, and the epidermal growth factor-binding protein. HCII inhibited leukocyte cathepsin G slowly, with a rate constant of 8 X 10(4) M-1 min-1 in the presence of dermatan sulfate. These results indicate that the protease specificity of HCII is more restricted than that of other plasma protease inhibitors and suggest that the anticoagulant effect of dermatan sulfate is due solely to inhibition of thrombin by HCII.
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PMID:The protease specificity of heparin cofactor II. Inhibition of thrombin generated during coagulation. 383 15

The aim of these studies was to investigate different regimens of thrombolytic therapy and oral anticoagulation, and to evaluate the effects of streptokinase (SK), heparin and warfarin in the treatment of deep vein thrombosis (DVT). Low-dose SK, although controlled according to the fibrinogen levels, did not provide improved thrombolysis compared to conventional high-dose SK, and more postthrombotic changes were registered after an average of 3 years. Furthermore, serious hemorrhagic side-effects occurred, which makes this regimen inexpedient. Various regimens of local venous infusion of SK were tried, and with a dose of 4,000 IU/h for 72 h in combination with heparin a thrombolytic effect was achieved, albeit not greater than usually observed with conventional SK. Systemic hypofibrinogenemia and hemorrhage were not avoided. A hitherto not described side-effect with bullous dermatitis was reported. Venographic severity of calf vein thrombosis displayed a statistically significant correlation to long-term hemodynamic changes, as assessed with foot volumetry, after an average of 5 years. This correlation was stronger for the size of the thrombus after initial treatment than for the size at diagnosis. Thus it seems important to treat calf vein thrombosis with heparin in order to limit the extent of the thrombus, thereby reducing long-term sequelae. During heparin treatment, an average reduction of the thrombi of 17% was observed. This reduction was significantly correlated to a short duration of symptoms but not to parameters of heparin therapy or fibrinolytic components. However, patients with substantial thrombolysis had high plasmin-alpha 2-antiplasmin (PAP) levels, and those with high tissue plasminogen activator (t-PA) inhibitor levels and remarkably also those with high t-PA antigen levels had no lysis. The concentration of t-PA antigen showed a significant increase during heparin infusion, whereas that of PAP and t-PA inhibitor was not influenced. By applying more intensive initial oral anticoagulation, stable therapeutic prothrombin time (PT)-levels were achieved one day earlier and the duration of heparin infusion could be equally reduced compared to the conventional regimen (4.4-5 days vs 5.4-6 days). The activity of coagulation factors II, VII, IX and X had dropped to the same level with both regimens the day heparin was discontinued, observed. The effectiveness of oral anticoagulation after DVT was studied in 596 patients treated for a total of 4450 months.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Studies on the medical treatment of deep vein thrombosis. 391 82

Twelve amino acid sequences of kringle-forming polypeptides were compiled from the known sequences of urokinase A-chain (human), a tissue-type plasminogen activator (human), prothrombin (human and bovine), and plasminogen (human). Their sequence homologies with maximum match were examined by a computer program. A homology alignment and graphic matrix analyses did show that they had a great degree of homology. All the cysteine residues responsible for the kringle structures of urokinase and the tissue-type plasminogen activator were confidently preserved as well as other proteins. A phylogenetic tree was then reconstructed, and the A- and S-chain of bovine and human prothrombins were accounted for the measurement of the evolutionary time span. It was found that urokinase had a larger time span, as much as 60 million years (MY), than the tissue-type plasminogen activator. A common ancestral element of the kringle-related serine proteases was placed at around 500 MY ago, as old as the diversion of the alpha- and beta-chains of hemoglobin. Thus, the kringle-families have undergone a substantial evolutionary divergence. Moreover, they can be subgrouped into three subfamilies: plasminogen activators, plasminogen, and prothrombin A-chains, the last being the most distantly diverged prothrombin S-chains.
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PMID:Homology of kringle structures in urokinase and tissue-type plasminogen activator: the phylogeny with the related serine proteases. 393 78

This study was performed to characterize selected pharmacologic properties and effects on the fibrinolytic system of tissue-type plasminogen activator synthesized by recombinant DNA technology (rt-PA) in 12 patients treated for coronary thrombosis. rt-PA was infused parenterally (by the intracoronary route in four patients and intravenously in eight) in doses of 8.3, 12.5, or 16.7 micrograms/kg/min for 30 to 60 min, yielding a total dosage of 20 to 40 mg/patient. The drug induced coronary thrombolysis in 10 of the 12 patients treated (83%), including six of the eight given rt-PA intravenously. No bleeding complications were encountered. Serial blood samples were obtained before, during, and after infusion of rt-PA and analyzed for t-PA antigen (i.e., immunoassayable rt-PA protein), functional fibrinolytic activity attributable to rt-PA, fibrinogen, plasminogen, alpha 2-antiplasmin, fibrinogen degradation products, prothrombin time, activated partial thromboplastin time, and protamine-corrected thrombin time. Pretreatment plasma t-PA antigen levels averaged 16.5 +/- 5(SD) ng/ml. Peak plasma values were generally proportional to dose, averaging 3330 +/- 1201 ng/ml. Approximately 90% of peak level was reached in 30 min, with a plateau at peak reached within 40 min. Functional t-PA activity increased monotonically in a comparable fashion. Curves for disappearance of both t-PA antigen and functional activity from plasma were monoexponential for at least two half-lives (r = .99 for both) and were concordant. The observed half-lives were similar, averaging 8.3 and 9.1 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Clinical pharmacology in patients with evolving myocardial infarction of tissue-type plasminogen activator produced by recombinant DNA technology. 403 68

A simple RIA method for B beta 15-42 RPs has been evaluated in our laboratory to investigate experimental and clinical fibrinolytic states. The assay utilizes bentonite precipitation to remove cross-reacting fibrinogen. Due to the heterogeneity in molecular weights of the B beta RPs, the results are expressed as nanograms per milliliter. The linear range of the assay is 2 to 40 ng/ml, with a capability of detecting up to 200 ng/ml. A special anticoagulant mixture (heparin or EDTA/aprotinin) is required for sample collection. Certain precautions in the care and handling of specimens are also necessary. Increased levels of B beta RPs were observed in the following conditions: malignancy (associated with increased release of tissue plasminogen activators), pancreatitis, liver diseases, pregnancy, and postexercise testing (associated with increased release of tissue plasminogen activators). Increased levels of B beta RPs were also found during thrombolytic therapy, anabolic steroid treatment, prothrombin complex concentrate therapy, blood component therapy, and low molecular weight heparin subcutaneous therapy (associated with an increase in tissue plasminogen activator release). Our studies suggest that B beta RPs are sensitive molecular markers of the endogenous activation of fibrinolytic system and may provide useful diagnostic information on a pathologic process that often remains undetectable by routine laboratory methods.
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PMID:Diagnostic efficacy of a simple radioimmunoassay test for fibrinogen/fibrin fragments containing the B beta 15-42 sequence. 651 20

Aprotinin reduces blood loss after cardiopulmonary bypass, but may sensitize recipients and is expensive. Tranexamic acid, a synthetic antifibrinolytic, has less disadvantages, but opinions differ regarding its efficacy. We studied three groups of patients undergoing cardiopulmonary bypass for coronary disease: recipients of aprotinin (total dose 4.2 x 10(6) kallikrein inhibiting units, n = 14), recipients of tranexamic acid (total dose 20 mg/kg body weight, n = 15), and nonmedicated controls (n = 14) during 24 hours after cardiopulmonary bypass. Compared with controls, aprotinin reduced blood loss, the number of patients requiring transfusions, and the mean number of transfused red cell units (all with p < 0.05), whereas the recipients of tranexamic acid did not differ either from aprotinin recipients or from controls. Aprotinin and tranexamic acid both mitigated the early postoperative reduction of adenosine diphosphate-induced platelet aggregation seen in the controls (p < 0.05). Postoperative increases of plasma concentrations of the prothrombin activation fragment F1 + 2 and the thrombin-antithrombin III complex showed an activation of intravascular coagulation, without any intergroup differences. The balance between concentrations of tissue plasminogen activator and the type 1 plasminogen activator inhibitor disclosed an activation of fibrinolysis, without differences between the groups. The concentrations of D-dimer, a breakdown product of cross-linked fibrin, remained at baseline in the recipients of aprotinin and tranexamic acid but tripled in the controls (p < 0.05). By contrast, the plasma antiplasmin activity was equally depressed in the tranexamic acid and the control groups but decreased less in the recipients of aprotinin (p < 0.05). This discrepancy may reflect the different modes of action of the two agents, which may make aprotinin more efficacious than tranexamic acid in the "nonfibrinolytic" act of protecting platelet function against attack by plasmin during cardiopulmonary bypass.
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PMID:Comparison of the effects of aprotinin and tranexamic acid on blood loss and related variables after cardiopulmonary bypass. 752 12

We compared peritoneal dialysis effluents from 18 CAPD patients who had not suffered from peritonitis during the last 6 months (group 1) with the effluents from five patients with acute peritonitis (group 2), measuring activation markers of coagulation and fibrinolysis. These markers included prothrombin fragment F1 + 2 (F1 + 2), thrombin-antithrombin III complex (TAT), fibrin monomer (FM), and fibrin degradation products (FbDP). In the dialysate of group 1 we found remarkably high levels of F1 + 2, TAT and FM concomitant with a high concentration of FbDP, indicating a high rate of intraperitoneal fibrin turnover. The balance between peritoneal generation and degradation of fibrin was disturbed in untreated patients of group 2, who had significantly higher levels of coagulation markers and a higher ratio between FM and FbDP. Seven days after treatment with intraperitoneal administration of antibiotics and heparin, F1 + 2, TAT, FM and FbDP decreased significantly. To evaluate the role of mesothelial cells (MC) in the high peritoneal fibrin turnover we investigated the expression of tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), plasminogen activator inhibitor type-1 (PAI-1), and tissue factor in cultured human peritoneal MC under basal conditions and after exposure to tumour necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), or bacterial lipopolysaccharide (LPS). The exposure of MC to TNF alpha or to a lesser extent IL-1 alpha or LPS reduced their fibrinolytic activity by decreasing t-PA production and increasing PAI-1 synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Imbalance between intraperitoneal coagulation and fibrinolysis during peritonitis of CAPD patients: the role of mesothelial cells. 756 82


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