Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Exposure of purified Hageman factor (HF, Factor XII) to phenylglyoxal hydrate (PHG), an agent reacting with arginine residues in protein, inhibited its coagulant properties upon subsequent exposure of negatively charged agents. Once HF had been exposed to kaolin or ellagic acid, however, subsequent addition of PHG was much less inhibitory. PHG had no effect upon the ability of HF to bind to negatively charged surfaces. PGH also inhibited preparations of activated PTA (Factor XI) and thrombin, and, when incubated with plasma, reduced the titer of coagulable fibrinogen, PTA Christmas factor (Factor IX), antihemophilic factor (Factor VIII), Factor VII, Stuart factor (Factor X), proaccelerin (Factor V) and prothrombin (Factor II), and to a lesser degres, HF.
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PMID:Inhibition of Hageman factor, plasma thromboplastin antecedent, thrombin and other clotting factors by phenylglyoxal hydrate (38500). 23 67

Plasma proteins which interfere with blood coagulation have often been described in patients with systemic lupus erythematosus (SLE). The most frequent type interferes with the conversion of prothrombin to thrombin and thus prolongs the prothrombin time. Infrequently, SLE patients exhibit anticoagulants which appear to block the earlier stages of coagulation such as those involving factor VIII or the formation of activated factor XI (factor XIa). The anticoagulant reported here was studied by means of a sequential clotting system utilizing crude coagulation factors and was noted to interfere with the action of activated plasma thromboplastin antecedent (PTA) during the activation of factor IX. This anticoagulant was found in gamma-globulin-rich ethanol fractions of plasma. After gel filtration, it was found principally in fractions containing IgM globulins but also, to a lesser extent, in IgG-rich fractions. In this respect, it is similar to anticoagulants reported in certain other cases of SLE. Attempts to confirm the immunoglobulin nature of the anticoagulant by immunoabsorption were, however, inconclusive
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PMID:Studies on a circulating anticoagulant in systemic lupus erythematosus: evidence for inhibition of the function of activated plasma thromboplastin antecedent (factor XIa). 23 89

Serial coagulation studies were performed in 26 pediatric patients with acute lymphoblastic leukemia during initial induction therapy with vincristine, prednisone, and L-asparaginase. Prolongation of screening coagulation tests was frequent: prothrombin time (in 16 of 26 patients), partial thromboplastin time (23/26) and thrombin time (21/26). In all 26 patients fibrinogen levels fell below .20 g/100 ml and 16 had levels below .10 g/100 ml. Sixteen patients had plasma coagulation factor assays performed. In these 16 patients, Factor XI was less than 40% in 14 and Factor XI was less than 70% in 9, with only a few scattered low levels of other factors. There were no clinical bleeding episodes. Coagulation abnormalities returned to normal at the completion of L-asparaginase therapy while the patients remained on vincristine and prednisone.
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PMID:The effect of L-asparaginase of plasma coagulation factors in acute lymphoblastic leukemia. 26 3

A study was carried out on mechanisms, independent of activated Factor XI, capable of activating Factor IX. The reaction product of tissue factor and Factor VII functioned as a potent Factor IX activator in the assay system used. Activated Factor IX itself activated Factor X; thrombin failed to activate Factor IX. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis confirmed that the reaction product of tissue factor and Factor VII activated Factor IX, with replacement of the band corresponding to native factor IX [molecular weight (Mr) 55,000] by bands corresponding to the heavy chain (Mr 27,000) and light chain (Mr 17,000) of activated Factor IX. When either Factor VII or calcium ions were left out of incubation mixtures, the band of native Factor IX persisted unchanged. Contact of blood with tissue factor represents a second mechanism, bypassing activated Factor XI, for the activation of Factor IX during hemostasis. It may help to explain the discrepancy between the mild bleeding of hereditary Factor XI deficiency and the severe bleeding of hereditary Factor IX deficiency.
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PMID:Activation of factor IX by the reaction product of tissue factor and factor VII: additional pathway for initiating blood coagulation. 27 51

A lupus-type anticoagulant which causes strong inhibition of the partial thromboplastin time with kaolin (PTTK), the stypven time, and the thrombin generation tests has been investigated. All tests for platelet function were normal, as were all specific coagulation factor assays with the exception of a slightly reduced factor XI in this patient. A diethylaminoethyl-cellulose-immunoglobulin (DEAE-cellulose-IgG) fractionation of the patient's plasma produced two peaks containing inhibitory activity in the PTTK test. The first of these peaks had a cloudy appearance, suggesting the presence of immunoglobulin aggregates. Studies with IgG aggregates prepared from normal IgG and from the patient's IgG demonstrated that such aggregates were not the cause of inhibition. It was possible to neutralize the inhibitory activity of the purified IgG but not platelet-poor plasma (PPP) with a rabbit anti-IgG. The inhibition of the patient's PPP in the thrombin generation, the contact product, and the stypven time tests were corrected by the inclusion in the test system of platelets activated either by aggregation due to adenosine diphosphate (ADP) or formalin fixation and washing. These studies lend support to earlier findings that platelets interact at several sites in the coagulation cascade.
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PMID:Demonstration of a platelet bypass mechanism in the clotting system using an acquired anticoagulant. 73 36

Partially purified human antihemophilic factor (AHF, factor VIII), when treated with high concentrations of salt, has been shown to dissociate into two components: one, of relatively low molecular weight, possesses procoagulant activity, and the other, of higher molecular weight, forms precipitates with heterologous antiserum against AHF and supports ristocetin-induced platelet aggregation. The ease of separation suggests that the two components in the native state might be held together by noncovalent bonds. Earlier observations do not exclude the possibility that the subunits may be covalently bonded in nature but might be severed by plasma proteolytic enzymes during laboratory manipulation. The issue was examined by preparing partially purified AHF from fresh human plasma in the presence of protease inhibitors, including benzamidine, soybean trypsin inhibitor, epsilon-aminocaproic acid, heparin, and hirudin. Under these conditons, gel filtration in the presence of 0.25 M calcium chloride and 0.001 M benzamidine resulted in its separation into two components, having properties identical to those separated in the absence of these protease inhibitors. The inhibitor mixture blocked generation and action of streptokinase- and kaolin-activated plasmin from plasma, and protected both plasma AHF and partially purified AHF from the action of thrombin. Surface-induced activation of PTA (factor XI) was partially inhibited, and that of Christmas factor (factor IX) was completely inhibited. This observation provides further evidence that in the native state the high- and low-molecular-weight components of preparations of antihemophilic factor are held together by noncovalent bonds.
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PMID:Evidence that functional subunits of antihemophilic factor (Factor VIII) are linked by noncovalent bonds. 94 7

Collagen is believed to be involved in the initial events in haemostasis and has been shown by others to cause platelet aggregation and release, and also to initiate the intrinsic pathway of coagulation. The present experiments provide evidence whihc suggests how these many effects of collagen may be involved in haemostasis. It is shown here that collagen releases platelet constituents by two different pathways. Collagen causes platelets washed free of loosely adsorbed coagulation factors to release constituents. This activity, is therefore, independent of the intrinsic pathway of coagulation, and is not inhibited by heparin or hirudin. Collagen also releases platelet constituents by an alternative pathway which is inhibited by heparin and hirudin and is independent of factor XII, but is dependent on factor XI, subsequent factors in the intrinsic pathway of coagulation and calcium. These results suggest that collagen-induced release of platelet constituents is in part due to a direct effect on the platelet, and , in part, to an indirect effect involving coagulation factors and mediated by thrombin. The present results suggest that irreversible aggregation by collagen is also mediated by thrombin. The possible significance of this dual action of collagen in the haemostatic process is shown in Fig 7.
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PMID:Evidence that colagen releases human platelet constituents by two different mechanisms. 95 63

Blood clotting and fibrinolytic systems were studied in the plasma of a sei whale (Balaenoptera borealis). The sei whale belongs to the suborder baleen whales of the order Cetacea. Whale plasma had a greatly prolonged kaolin-activated partial thromboplastin time and was deficient in Hageman factor (factor XII), Fletcher factor (a plasma prekallikrein), and PTA (factor XI). All other clotting factor activities were present in amounts comparable to that of normal human plasma. Whale plasminogen was activated by human urokinase, but not by streptokinase. Whale plasma contained inhibitory activities against thrombin, activated Stuart factor, activated PTA, activated Fletcher factor, and plasmin.
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PMID:Studies on the blood clotting and fibrinolytic system in the plasma from a sei (baleen) whale. 96 76

Isolated deficiencies of factors VII and XI are both rare. Not surprisingly, therefore, combined factor VII and XI deficiency has not been reported previously. We report here a kindred with a combined heterozygous deficiency for both factors VII and XI. The proposita is a 28-year-old woman who had both a prolonged prothrombin time (PT) and a prolonged activated partial prothrombin time (APTT) associated with a mild bleeding tendency. Coagulation studies were performed on the six available members of this kindred. The PT and APTT were normal or mildly abnormal in five of these individuals. Factor VII coagulant activity (VII:C) varied from 0.33 to 0.77 units/ml in affected subjects. In contrast, the concentration of factor VII-related antigen for the six individuals ranged from 0.68 to 2.10 units/ml. Comparable factor VII:C levels were obtained when each subject's plasma was tested with either a rabbit or a human thromboplastin reagent. Factor XI coagulant activity was less than 0.5 units/ml in three of the six subjects and normal (approximately 1.0 units/ml) in the other three. The concentrations of thrombin-antithrombin-III and prothrombin fragment 1.2 were within normal limits for all individuals. In addition to being associated with heterozygous factor XI deficiency, the abnormal factor VII molecule in the plasma of affected individuals in this kindred appears to represent a newly described mutation. This is suggested by the pattern of reactivity with thromboplastin from different species, the normal tissue factor binding and the bleeding tendency in heterozygous individuals in this kindred.
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PMID:A novel congenital haemostatic defect: combined factor VII and factor XI deficiency. 148 4

The intrinsic pathway of blood coagulation is activated when factor XIa, one of the three contact-system enzymes, is generated and then activates factor IX. Factor XI has been shown to be efficiently activated in vitro by surface-bound factor XIIa after factor XI is transported to the surface by its cofactor, high molecular weight kininogen (HK). However, individuals lacking any of the three contact-system proteins--namely, factor XII, prekallikrein, and HK--do not suffer from bleeding abnormalities. This mystery has led several investigators to search for an "alternate" activation pathway for factor XI. Recently, factor XI has been reported to be autoactivated on the soluble "surface" dextran sulfate, and thrombin was shown to accelerate the autoactivation. However, it was also reported that HK, the cofactor for factor XIIa-mediated activation of factor XI, actually diminishes the thrombin-catalyzed activation rate of factor XI. Nonetheless, it was suggested that thrombin was a more efficient activator than factor XIIa. In this report we investigated the effect of fibrinogen, the major coagulation protein in plasma, on the activation rate of factor XI. Fibrinogen, the preferred substrate for thrombin in plasma, virtually prevented autoactivation of factor XI as well as the thrombin-mediated activation of factor XI, while having no effect on factor XIIa-catalyzed activation. HK dramatically curtailed the autoactivation of factor XI in addition to the thrombin-mediated activation. These data indicate that factor XI would not be autoactivated in a plasma environment, and thrombin would, therefore, be unlikely to potentiate the activation. We believe that the "missing pathway" for factor XI activation remains an enigma that warrants further investigation.
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PMID:Fibrinogen blocks the autoactivation and thrombin-mediated activation of factor XI on dextran sulfate. 145 98


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