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)

To determine whether children treated with chronic peritoneal dialysis have a hypercoagulable state, various coagulation and fibrinolytic factor concentrations or activities were measured in 17 children undergoing chronic peritoneal dialysis. The patients had significantly increased activities of factors VII and VIII, and increased concentrations of von Willebrand factor (vWF), fibrinogen, factor XIIIA and factor XIIIS compared to reference values (P less than 0.001 in each case). The activated partial thromboplastin time was prolonged (P less than 0.001) and the thrombin clotting time was decreased (P less than 0.05) in these children. The prothrombin time and activities of factors XII, XI, IX, X, V and II were not significantly different from control values. Protein C concentrations were similar to normal, but antithrombin III concentrations were increased (P less than 0.05). Within the fibrinolytic pathway, decreased concentrations of plasminogen were found (P less than 0.001) and the concentrations of alpha-2-antiplasmin were increased (P less than 0.001). The plasma albumin concentration was below 33 g/l in 13 of the 17 children. The duration of treatment with peritoneal dialysis was directly correlated with vWF concentrations (P less than 0.001) and inversely correlated with factor VII concentrations (P less than 0.01). Of these patients 2 have since had clinical thrombotic episodes. The coagulation abnormalities found may have a role in the occurrence of thrombosis complicating renal transplantation.
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PMID:Coagulation abnormalities in chronic peritoneal dialysis. 239 81

The efficacy of three different protein C activity assays and of protein C antigen determination for the diagnosis of protein C deficiency was studied in 13 protein C deficient patients (11 with type I, 2 with type II deficiency) and in 51 presumably non-deficient patients (control group), both groups being on oral anticoagulant (OAC) treatment. For protein C activity measurement (1) the assay according to Francis (slightly modified) with thrombin activation and measurement of activated protein C in the aPTT system, (2) an assay using Protac activation and chromogenic substrate (Protac-CS) and (3) an assay using Protac activation and the aPTT system (Protac-PTT) were used. Protein C antigen was determined by Laurell immunoelectrophoresis. The three activity assays gave different results, with the highest values obtained by the Protac-CS assay and the lowest values by the Protac-PTT assay. The Francis assay gave intermediate results. Protein C activity and antigen values were significantly lower in protein C deficient patients compared to the control group. Protein C activity tests had a higher discriminative power than the antigen determination. After taking into account the intensity of treatment, by the Francis assay all deficient and non-deficient patients were correctly classified, by the Protac-CS and the Protac-PTT assay 2 and 4 patients, respectively, were misclassified and by the antigen assay 8 patients were misclassified. Calculation of the ratios of protein C activity to factor II activity was of high discriminative power. We conclude that for diagnosis of protein C deficiency protein C activity tests are superior to antigen determination not only in type II but also in type I deficient patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Diagnosis of protein C deficiency in patients on oral anticoagulant treatment: comparison of three different functional protein C assays. 240 42

Protein C, like the other vitamin K-dependent plasma proteins that participate in blood coagulation, except prothrombin, has at least one high affinity calcium-binding site that is independent of gamma-carboxyglutamic acid. Calcium binding to this site is required for activation of protein C by the thrombin-thrombomodulin complex. In an attempt to localize this calcium-binding site, we subjected protein C to limited tryptic digestion. A monoclonal antibody that recognizes a calcium-dependent epitope both in intact protein C, in gamma-carboxyglutamic acid-domainless protein C, and in activated protein C, was used to isolate a fragment from the tryptic digest. The fragment was derived from the light chain of protein C and consisted of the two domains that are homologous to the epidermal growth factor precursor. Half-maximal binding of the intact protein and of the isolated fragment by the antibody occurred at 100-200 microM Ca2+. The results suggest the presence of a Ca2+-binding site in the epidermal growth factor homology region of protein C.
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PMID:Calcium-dependent interaction between the epidermal growth factor precursor-like region of human protein C and a monoclonal antibody. 244 97

Protein C undergoes Ca2+-induced conformational changes required for activation by the thrombin-thrombomodulin complex. A Ca2+-dependent monoclonal antibody (HPC4) that blocks protein C activation was used to study conformational changes near the activation site in protein C. The half-maximal Ca2+ dependence was similar for protein C and gamma-carboxy-glutamic acid-domainless protein C for binding to HPC4 (205 +/- 23 and 110 +/- 29 microM Ca2+, respectively), activation rates (214 +/- 22 and 210 +/- 37 microM), and intrinsic fluorescence of gamma-carboxyglutamic acid-domainless protein C (176 +/- 34 microM). Protein C heavy chain binding to HPC4 was half-maximal at 36 microM Ca2+, although neither the heavy chain nor HPC4 separately bound Ca2+ with high affinity. The epitope was lost when the activation peptide was released. A synthetic peptide, P (6-17), which spans the activation site, exhibited Ca2+-dependent binding to HPC4 (half-maximal binding = 6 microM Ca2+). Thus, each decrease in antigen structure resulted in a reduced Ca2+ requirement for binding to HPC4. Tb3+ and Ca2+ binding studies demonstrated a Ca2+-binding site in HPC4 required for high affinity antigen binding. These studies provide the first direct evidence for a Ca2+-induced conformational change in the activation region of a vitamin K-dependent zymogen. Furthermore, Ca2+ binding to HPC4 is required for antigen binding. The multiple roles of Ca2+ described may be useful in interpretation of other metal-dependent antibody/antigen interactions.
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PMID:The interaction of a Ca2+-dependent monoclonal antibody with the protein C activation peptide region. Evidence for obligatory Ca2+ binding to both antigen and antibody. 244 82

We report a prospective study in nine consecutive adult patients with acute promyelocytic leukaemia (APL). The study objective was to assess the prevalence of activation of blood coagulation and/or activation of fibrinolysis in APL. Coagulation and fibrinolytic parameters relevant to the objective included antithrombin III, plasminogen, fibrin/fibrinogen degradation products and alpha-2 antiplasmin activity and antigen levels. The results of this study revealed consistently normal antithrombin III levels, both before and in the course of antileukaemic treatment. Plasminogen levels were slightly decreased or normal. However, a distinct alpha-2 antiplasmin activity deficiency in all patients was observed with levels even reaching zero in three patients, during chemotherapy. Alpha-2 antiplasmin activity levels were consistently lower than the alpha-2 antiplasmin antigen levels. The in vitro binding of alpha-2 antiplasmin activity to fibrin clots was severely reduced which appeared to be due to the reduced alpha-2 antiplasmin plasma levels. Upon crossed-immunoelectrophoresis against alpha-2 antiplasmin antiserum two alpha-2 antiplasmin antigen peaks were observed in the plasma of all nine patients. All abnormalities were reversible 4 d after completion of chemotherapy. In a second series of 12 consecutive APL patients we confirmed the consistency of the alpha-2 antiplasmin activity deficiency and normal antithrombin III plasma levels. In addition Protein C activity and antigen levels were normal or near normal in 10 and reduced in two patients. Thrombin-antithrombin III complexes were increased in 10 and normal in two patients. We conclude that some activation of blood coagulation is present in APL (increased thrombin-antithrombin III complex levels) but its contribution to the coagulopathy seems to be minor (normal antithrombin III and only slightly reduced protein C levels). The observed reduced alpha-2 antiplasmin content of the fibrin clot in vitro may result in vivo in a fibrin clot that is highly susceptible to fibrin degradation, thus aggravating the coagulopathy in APL.
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PMID:Acquired alpha-2-antiplasmin deficiency in acute promyelocytic leukaemia. 246 Jan 26

A patient with microvascular thrombosis and thrombocytopenia was found to have a high-titre lupus anticoagulant. The biological effects of the patient's lupus anticoagulant were studied using whole patient serum and plasma. Staph Protein A eluate, and affinity-purified lupus anticoagulant. The latter was isolated by immunoadsorption of serum onto cardiolipin/phosphatidylserine/cholesterol liposomes. Each source of lupus anticoagulant demonstrated 'anticoagulant' activity, defined as prolongation of a modified kaolin clotting time, and contained antibody which bound to endothelial monolayers. Each interfered with thrombin-mediated prostacyclin release from endothelial cells, but had no effect on arachidonate-induced prostacyclin release. In addition, the lupus anticoagulant selectively blocked platelet aggregation in response to thrombin, but not in response to arachidonate, ADP or epinephrine. Lupus anticoagulant also reduced thrombin-stimulated shifts in cytosolic calcium. Thrombin-mediated membrane inositol metabolism and total thrombin binding to endothelium were unaffected by lupus anticoagulant, and another endothelial anticoagulant function related thrombin binding. Protein C activation by thrombomodulin, was not altered. We conclude that the binding of lupus anticoagulant to endothelial cells and platelets does not prevent all thrombin signalling events, but does interrupt prostacyclin production.
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PMID:Lupus anticoagulant induces a selective defect in thrombin-mediated endothelial prostacyclin release and platelet aggregation. 249 19

The profile of blood coagulation and fibrinolysis was studied in detail in eight patients with acute thrombotic thrombocytopenic purpura (TTP). In the majority of the patients, fibrinogen, factor XIII, antithrombin III, alpha 2-plasmin inhibitor, plasminogen, and alpha 2-macroglobulin were normal, whereas FDP, plasmin-alpha 2-plasmin inhibitor complex, and tissue-type plasminogen activator antigen were marginally or moderately elevated. Low fibronectin values were observed in four patients. Protein C and C4b-binding protein were nearly normal, whereas total protein S and free protein S were reduced in five and six patients, respectively. A positive correlation was found between total protein S and C4 and between free protein S and C3. von Willebrand factor antigen (vWf:Ag) and ristocetin cofactor (RCof) were either normal or elevated, but RCof/vWf:Ag ratio was decreased in seven patients. Crossed immunoelectrophoresis and sodium dodecyl sulfate (SDS)-agarose gel electrophoresis revealed that the large vWf multimers were either absent from or relatively decreased in all patients except one. In addition, one patient had unusually large vWf multimers, and a low-molecular-weight vWf fragment was apparently observed in three patients. These findings indicate that the intravascular generation of thrombin and plasmin was minimal in TTP and suggest that the alterations of the vWf molecule were caused not only by consumption through its participation in platelet thrombus formation but also by accelerated proteolysis. Low protein S values would be related to the immunological abnormalities underlying TTP.
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PMID:Coagulation studies in thrombotic thrombocytopenic purpura, with special reference to von Willebrand factor and protein S. 252 Dec 76

Protein C activation by alpha-thrombin on the surface of endothelial cells depends on an essential membrane-glycoprotein cofactor, thrombomodulin. In the present study we have monitored the activity of thrombin-thrombomodulin complexes on human saphenous-vein endothelial cells (HSVEC) or on the endothelial cell line EA.hy 926. Cell monolayers were exposed for 5 min to 8.5 nM human alpha-thrombin and then washed to remove unbound thrombin. The cells were then incubated at 37 degrees C for 5-180 min. At the end of the respective incubation periods, purified human protein C (120 nM) was added in order to assay the activity of the thrombin-thrombomodulin complexes present on the cell surface. HSVEC pre-exposed to thrombin retained their full capacity to promote protein C activation up to 90 min after free thrombin was removed. This capacity then decreased slowly to reach 56% of control value after 180 min of incubation. Original activity was 3.8 +/- 0.9 pmol of activated protein C formed/min per ml per 10(6) cells (mean +/- S.E.M., n = 5). The capacity of protein C activation of EA.hy 926 cells remained constant for 120 min after free thrombin was removed, then decreased to 76% of control after 180 min. Original activity was 2.0 +/- 0.4 pmol of activated protein C formed/min per ml per 10(6) cells (mean +/- S.E.M., n = 3). Similar results were obtained with cells fixed with 3% paraformaldehyde. However, during the 5-180 min incubation period, non-fixed cells of both types were capable of significantly internalizing fluorescent acetylated low-density lipoprotein. In the experimental protocol used here, an eventual inhibition of thrombin internalization by protein C can be excluded, as protein C is only added at the end of the incubation period. We conclude that there is no evidence of rapid internalization of thrombin-thrombomodulin complexes on HSVEC or the EA.hy 926 cell line, as assessed by the ability of membrane-bound thrombin to activate protein C.
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PMID:Stability of the thrombin-thrombomodulin complex on the surface of endothelial cells from human saphenous vein or from the cell line EA.hy 926. 254 86

A complex composed of factor Xa and phospholipid vesicles assembled in the presence of calcium ions catalyzes a discrete cleavage of the heavy chain of bovine protein C that is indistinguishable from that produced by thrombin as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This cleavage generates an active site capable of hydrolyzing small substrates and inactivating factor Va function in the prothrombinase complex. Activation of protein C by factor Xa requires both calcium ions and phospholipid vesicles and proceeds at a rate an order of magnitude greater than that observed for alpha-thrombin in solution. gamma-Carboxyglutamic acid-domainless protein C is not activated by factor Xa, consistent with the requirement for phospholipid and distinguishing this reaction from protein C activation by thrombin. Thrombomodulin serves as a cofactor for the factor Xa-catalyzed reaction, forming a 1:1 complex with factor Xa (apparent Kd = 5.7 X 10(-10) M) and stimulating the saturated rate of protein C activation by factor Xa (kcat = 149 min-1) to levels comparable with the thrombin-thrombomodulin complex. Protein C activation by factor Xa is not inhibited by the specific thrombin inhibitor dansyl-N-(3-ethyl-1,5-pentanediyl)amide but is inhibited by antithrombin III, tripeptide-chloromethyl ketones, and the monoclonal antibody alpha-BFX-2b that is highly specific for factor Xa. These data indicate that thrombomodulin is promiscuous in its role as a cofactor and suggest the existence of an alternative pathway for protein C activation in vivo.
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PMID:The activation of bovine protein C by factor Xa. 255 Apr 35

Changes in the protein C-thrombomodulin (PC-TM) system in relation to other coagulofibrinolytic parameters were examined in 25 patients undergoing open heart surgery. Although all patients were given heparin, a decrease in antithrombin III (ATIII) and progressive increase in thrombin-ATIII complex (TAT) and fibrinopeptide A (FPA) levels were noted during cardiopulmonary bypass, which indicated that heparinization did not completely inhibit the formation of thrombin and its function. C1-inactivator (INA) resistant fibrinolytic activity increased markedly during CPB, in parallel with the change of tissue plasminogen activator antigen (t-PA;Ag), which indicates that fibrinolytic activity during CPB is mainly of extrinsic origin caused by t-PA. Protein C antigen (PC;Ag), protein S antigen (PS;Ag), and thrombomodulin antigen (TM;Ag) were all decreased significantly during CPB. This is considered to reflect the activation and consumption of the PC-TM system in response to generated thrombin. Furthermore, enhancement of the extrinsic fibrinolytic system is easily explained by the action of activated PC, which counteracts plasminogen activator inhibitor (PAI-1), to cause enhancement of t-PA activity.
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PMID:The role of the protein C-thrombomodulin system in physiologic anticoagulation during cardiopulmonary bypass. 255 68


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