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)

Thrombin not only plays an important role in thrombosis and haemostasis but may also be involved in other pathological situations such as the progression of atherosclerotic plaque formation, inflammatory response and neurodegenerescence. It is therefore important to be able to control the action and/or the generation of this enzyme. With this aim in view, a great number of synthetic or recombinant direct thrombin inhibitors have recently been made. They block either the thrombin catalytic site or an anion-binding exosite which is a recognition site for some of its substrates (fibrinogen, thrombin receptor, thrombomodulin, heparin cofactor II) or act on both sites. Some of these inhibitors have revealed a number of advantages over heparin in experimental animal models of thrombosis and haemorrhagic risk. On-going clinical studies with some candidates will establish their real interest for patients.
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PMID:Direct thrombin inhibitors. 130 May 40

A patient with an 18 year history of recurrent arterial thrombosis and no evidence of atherosclerosis or embolism of cardiac origin presented with a prolonged thrombin clotting time when performed with human thrombin. The bovine thrombin clotting time was only slightly prolonged. During 30 months of follow-up, the thrombin time fluctuated, but remained prolonged. The patient has been treated with an oral anticoagulant for the past 8 years, with no thrombotic recurrence. The inhibitor activity was due to the presence of polyclonal IgGs which bound to thrombin-Sepharose. The influence of IgGs purified from the patient's serum was compared to the influence of normal IgGs in several systems exploring the catalytic activity of thrombin and the binding of the enzyme to macromolecular substrates through secondary binding site(s). We found that the IgGs did not impair the catalytic activity toward small synthetic substrates, but inhibited the binding of thrombin to fibrinogen, thrombomodulin and heparin cofactor II. Such proteins are known to require a secondary binding site of thrombin to interact with the enzyme. The anti-thrombin antibody might have resulted from an abnormal generation of thrombin. This would be the consequence of the process favouring thrombosis. Alternatively, the autoantibody might have favoured thrombosis primarily, by impairing natural antithrombotic mechanisms triggered by thrombin.
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PMID:Partial characterization of an autoantibody recognizing the secondary binding site(s) of thrombin in a patient with recurrent spontaneous arterial thrombosis. 132 Mar

The sick neonate may develop spontaneous or catheter-related thromboses, which must in part reflect poor regulation of the formation and activities of the coagulation enzyme, thrombin. We hypothesized that the balance between the generation and inhibition of thrombin may differ in sick neonates compared with healthy neonates. Fifty neonates with respiratory failure requiring mechanical ventilation and 40 healthy neonates were studied on d 1 of life. All neonates had normal coagulation screening tests and a platelet count greater than 150 x 10(9)/L. Plasma pools from neonates with similar gestational age (GA), birth weight, and health status were prepared. Eight plasma pools from 40 healthy neonates of GA 30-38 wk were compared with six plasma pools from 30 sick neonates of GA 30-38 wk. An additional four plasma pools prepared from 20 sick neonates of GA less than 30 wk were studied. Thrombin generation was measured by amidolysis of a chromogenic substrate, S2238, after defibrination, contact activation, and recalcification of the test plasmas. The contributions of antithrombin III, heparin cofactor II, and alpha 2-macroglobulin as inhibitors of 125I-thrombin were quantitated by SDS-PAGE followed by autoradiography and densitometry. Thrombin generation was similar for both healthy and sick neonates of GA 30-38 wk. However, the inhibition of thrombin was impaired in plasma from sick neonates of GA 30-38 wk compared with plasma from healthy neonates of GA 30-38 wk (4.37 +/- 0.22 versus 5.21 +/- 0.21 nmol; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Thrombin inhibition is impaired in plasma of sick neonates. 137 86

Plasminogen activator inhibitor 1 (PAI-1), a member of the serpin superfamily of proteins, has been demonstrated previously to interact functionally with the glycosaminoglycan heparin (Ehrlich, H.J., Keijer, J., Preissner, K. T., Klein Gebbink, R., and Pannekoek, H. (1991) Biochemistry 30, 1021-1028). Heparin specifically enhances the rate of association between PAI-1 and thrombin about 2 orders of magnitude, whereas no effect is detected with other serine proteases (e.g. factor Xa). For the heparin-dependent serpins antithrombin III and heparin cofactor II, basic amino acid residues in and around the helix D subdomain were proposed to be involved in the binding of glycosaminoglycans. Here we employed site-directed mutagenesis of full-length PAI-1 cDNA to identify the amino acid residues that mediate heparin binding. To that end, 15 single-point mutants of PAI-1, each having individual arginyl, lysyl, or histidyl residues replaced by a neutral (alanyl) residue ("ala-scan"), and one double mutant were constructed, expressed in Escherichia coli, and purified to apparent homogeneity. The purified biologically active proteins were subjected to the following analyses: (i) heparin-dependent inhibition of thrombin; (ii) heparin-dependent formation of sodium dodecyl sulfate-stable complexes with thrombin; and (iii) binding to and elution from heparin-Sepharose. Based on the data presented, we propose that the amino acid residues Lys65, Lys69, Arg76, Lys80, and Lys88 constitute major determinants for heparin binding of PAI-1. These residues are located in and around the helix D domain and are conserved in the other heparin-dependent thrombin inhibitors, antithrombin III and heparin cofactor II.
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PMID:Elucidation of structural requirements on plasminogen activator inhibitor 1 for binding to heparin. 137 44

Serum amyloid P protein (SAP) is a heparin-binding protein that is found in blood and connective tissues including some types of vascular basement membrane. In this article we present evidence that SAP is capable of blocking the anticoagulant effects of glycosaminoglycans. SAP neutralized the catalytic effect of heparin on the thrombin-antithrombin III reaction more effectively than vitronectin, histidine-rich glycoprotein, fibronectin, and high-molecular-weight kininogen and almost as effectively as platelet factor 4. SAP also blocked the effects of heparin and dermatan sulfate on the inhibition of thrombin by heparin cofactor II. We found evidence for the formation of a high-affinity 1:1 complex between SAP and heparin and for inhibition of binding of both thrombin and antithrombin III to heparin-Sepharose by SAP. We conclude that SAP may account for much of the heparin-neutralizing capacity of plasma under some conditions and that basement-membrane-bound SAP may modulate extravascular coagulation by blocking the anticoagulant effects of basement membrane glycosaminoglycans.
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PMID:Neutralization of the anticoagulant effects of glycosaminoglycans by serum amyloid P component: comparison with other plasma and platelet proteins. 137 16

Orgaran is a mixture of glycosaminoglycans extracted from animal mucosa. It consists of heparan, dermatan and chondroitin sulfate; a small proportion of heparan sulfate (4%) has high affinity for antithrombin III (AT III). Orgaran is devoid of heparin or heparin fragments. Orgaran catalyses the inactivation of factor Xa and thrombin. Compared to heparin and most low-molecular-weight heparins, Orgaran has a much higher anti-Xa/anti-IIa ratio. The inactivation of factor Xa is mediated by AT III and that of thrombin by both AT III and heparin cofactor II. Compared to heparin, which is a strong inhibitor of thrombin generation, Orgaran has only moderate inhibitory effects on thrombin generation. Orgaran shows minimal or no effects on platelet function in vitro or in vivo. It inhibits the formation of various types of thrombi (clot-like and mixed thrombi) with approximately the same potency as heparin. Both the high- and low-affinity fraction for AT III contribute to the antithrombotic activity. In contrast to heparin, Orgaran does not inhibit platelet deposition in experimental mixed thrombi unless very high doses of the heparinoid are used. Orgaran is more efficacious than heparin in preventing the extension of established venous thrombosis. Orgaran promotes less bleeding-enhancing activity than heparin in various experimental models. In addition, compared to heparin, it has only minimal effects on platelet degranulation during hemostatic plug formation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Orgaran (Org 10172): its pharmacological profile in experimental models. 137 65

We investigated heparin cofactor II (HC II) levels and their relationship to other haemostatic factors in the elderly in comparison with antithrombin III (AT III). We measured plasma HC II activity levels in 166 subjects aged from 61 to 99 years using a chromogenic method. HC II levels (94.4 +/- 18.5%) in the healthy elderly subjects were significantly (p less than 0.001) lower than in 40 healthy adult controls under 60 years of age (mean age: 51.5 years; 111.6 +/- 21.2%). HC II levels in the elderly subjects decreased further with age (r = 0.308, p less than 0.001) and the extent of the decrease was more marked than that for AT III (r = 0.179, p less than 0.05). There was no significant sex difference in HC II levels in the elderly. HC II levels correlated significantly with AT III levels and with acute phase reactants including sialic acid, fibrinogen, and PAI-1. HC II levels also correlated with factor VII, plasminogen, alpha 2-plasmin inhibitor, serum lipid, pseudocholinesterase, and albumin levels. These correlations were also found for AT III except active PAI-1 and tPA-PAI-1 complexes, but the correlations with acute phase reactants were stronger for HC II than AT III. We divided 154 elderly subjects into 4 groups by their pseudocholinesterase and albumin levels to estimate the effect of nutritional status on antithrombin activity in the elderly. HC II levels were normal in the elderly subjects with a good nutritional state (103 +/- 18%), but were significantly decreased in those with malnutrition (85 +/- 15%, p less than 0.001). AT III levels also showed the same tendency. These results indicate a decrease in the reserve capacity to inhibit thrombin generation at sites of atherosclerosis in response to trigger events. The deficiency of two major antithrombin factors in the elderly may indicate a tendency to thrombosis, especially in individuals with malnutrition. When considering the clinical significance of HC II, several other parameters, including age, nutritional status, hepatic synthetic ability, and the presence or absence of acute phase reaction should also be assessed.
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PMID:Heparin cofactor II deficiency in the elderly: comparison with antithrombin III. 138 49

Three species of oversulfated fucans having different sulfate contents (the ratio of sulfate/total sugar residues, 1.38-1.98) were prepared by chemical sulfation of a fucan sulfate (sulfate/sugar ratio, 1.28) isolated from the brown seaweed Ecklonia kurome. The anticoagulant activities of the oversulfated fucans were compared with that of a parent fucan with respect to activated partial thromboplastin time (APTT) and thrombin time (TT) in plasma. The respective activities (for APTT and TT) of the oversulfated fucans increased to 110-119% and 108-140% of the original values with increase in their sulfate content. The anticoagulant activity with respect to APTT (173 units/mg) of an oversulfated fucan (sulfate/sugar ratio, 1.98) was higher than that (167 units/mg) of heparin used as a standard. The heparin cofactor II-mediated antithrombin activity of the oversulfated fucans also increased significantly with increase in sulfate content. The maximum activity was higher than those of the parent fucan and heparin. However, the increment of the anticoagulant and the antithrombin effects gradually decreased with increase in the sulfate content of the fucans. These results indicate that the effects of the fucan sulfate are dependent on its sulfate content until a plateau is reached.
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PMID:Anticoagulant and antithrombin activities of oversulfated fucans. 139 92

We measured plasma heparin cofactor II (HC II) activity in patients with disseminated intravascular coagulation (DIC) due to various underlying diseases together with the levels of antithrombin III (AT III), pseudocholinesterase (a marker of hepatic synthesis), and various haemostatic molecular markers. Both HC II and AT III were decreased in DIC secondary to all the underlying diseases studied, except acute promyelocytic leukemia (APL), when compared with healthy subjects. The lowest HC II and AT III levels was observed in coagulopathy secondary to liver disease, the HC II level in sepsis was the second lowest. In DIC due to APL, the decrease in HC II was not accompanied by a decrease in AT III. Thus, we divided all 124 samples tested into APL and non-APL groups. The HC II level correlated positively with fibrinogen and plasminogen in both the APL and non-APL groups. In the APL group, the HC II level had a significant negative correlation with the thrombin-AT III complex (TAT), fibrinogen/fibrin degradation products, and D-dimer levels as well as the prothrombin time, while AT III showed no correlations with any of the haemostatic parameters. These results suggest that HC II may be consumed preferentially by thrombin in APL patients with DIC, and thus may spare the consumption of AT III. Accordingly, HC II seems to be a superior indicator of DIC than AT III in APL patients. Moreover, replacement therapy with HC II instead of AT III may be useful to treat DIC associated with APL. In the non-APL group, the HC II levels were positively correlated with the levels of AT III and pseudocholinesterase activity. This indicates that plasma HC II levels are closely related not only to consumption coagulopathy but also to hepatic synthetic activity, as is the case for plasma AT III.
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PMID:Preferential consumption of heparin cofactor II in disseminated intravascular coagulation associated with acute promyelocytic leukemia. 141 8

Anticoagulation effect of chitosan sulfate ester and some mechanisms of its influence on hemostasis were studied in vitro. The chitosan sulfate ester catalyzed more effectively inactivation of the enzymes involved in the inner pathway of blood coagulation affecting only slightly the activity of outer pathway factors. The ester, similarly to heparin, inhibited blood coagulation mainly via accelerated thrombin inactivation by means of blood plasma antithrombin III. Inhibition of the enzyme coagulation activity using heparin cofactor II occurred only at high concentrations of chitosan sulfate ester in blood plasma. Besides, the ester decreased the thrombin catalytic activity in reactions with natural and synthetic peptide substrates. Thus, anticoagulation effect of chitosan sulfate ester is similar to that of heparin.
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PMID:[Mechanisms of anticoagulant effect of chitosan sulfuric acid ester]. 149 85


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