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

---

Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Determination of the complement titer in the serum and plasm of 120 patients with chronic liver diseases showed that in eight (7%) patients with cirrhosis of the liver, chronic active or chronic inactive hepatitis complement in the serum was less than half in the plasma. The dissociation of complement serum and plasma was due to cold activation of the classical pathway of complement in vitro since serum drawn from these patients at 37 degrees C lost hemolytic activity in 4 hours when transferred to a cold environment. Neither HB antigen nor cryoglobulin participated in this phenomenon. The activation of complement in the cold could be prevented by increasing the ionic strength, or by adding vitamin E or, to a lesser extent its vehicle HCO-60, while heparin, Trasylol, soybean trypsin inhibitor, or hirudin had no effect. Trans-AMCHA prevented activation in one case. It is speculated that a factor appearing as a result of blood clotting is able to activate the classical pathway of complement in the cold; it is probably not related to Hageman factor (factor XII), factor VII, thrombin, kallikrein.
...
PMID:Cold activation of complement i. presence of coagulation-related activator. 5 81

Changes of prekallikrein in the cases with DIC were investigated, i.e., DIC cases including disseminated metastasis of gastric cancer, acute promyelocytic leukemia and endotoxin shock. Therefore, the trigger substances for this paper were the pathologic cells of the leukemia, the cultured well differentiated adenocarcinoma cells and endotoxin. (1) The lysates of the pathologic cells of the leukemia and the cultured cells showed prekallikrein activation. Endotoxin showed prekallikrein activation via factor XII. (2) Serine proteases (factor Xa, thrombin, plasmin and trypsin) activated prekallikrein in the plasma and the purified prekallikrein. (3) Antithrombin III, aprotinin and FOY inhibited prekallikrein activation. Antithrombin III was promoted by heparin in its inhibitory effect.
...
PMID:Changes of prekallikrein in the cases with disseminated intravascular coagulation syndrome. 16 Jan 91

The effect of collagen on isolated platelets, platelet-rich plasma and whole blood has been studied. Collagen failed to generate factor XIa-like activity in mixtures of isolated platelets, collagen and Ca++. Moreover, collagen added to whole blood or platelet-rich plasma containing 125I-factor IX and Ca++, also failed to form cleaved (activated) factor IX. In preliminary studies, lysed endothelial cells were found to enhance the formation of factor Xa and thrombin and to induce cleavage of 125I-factor IX in normal plasma, factor XII and factor-XI-deficient plasma even in the presence of antibody to tissue factor.
...
PMID:The role of endothelial cells and subendothelial components in the initiation of blood coagulation. 51 Oct 12

Factor XII was purified approximately 14 000-fold from bovine plasma by ammonium sulfate fractionation followed by heparin-agarose, DEAE-Sephadex, CM-cellulose, arginine-agarose, and benzamidine-agarose column chromatography. By this method, about 15 mg of protein was purified from 15 L of plasma with an overall yield of 18%. The purified protein was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino-terminal analysis. Bovine factor XII is a glycoprotein with a mol wt of 74 000 as determined by sedimentation equilibrium centrifugation. It contains 13.5% carbohydrate including 3.4% hexose, 4.7% N-acetylhexosamine, and 5.4% N-acetylneuraminic acid. Factor XII is a single polypeptide chain with an NH2-terminal sequence of Thr-Pro-Pro-Trp-Lys-Gly-Pro-?-Lys-His. This sequence is homologous to the reactive-site regions of a number of protease inhibitors. The amino acid sequence of a carboxyl-terminal fragments prepared by cyanogen bromide digestion was found to be Leu-Cys-Ala-Gly-Phe-Leu-Glu-Gly-Gly-Thr-Asp-Ala-Cys-Gln-Gly-Asp-SER-Gly-Gly-Pro-Leu-Val-Cys-Glu-Asp-Glu. This sequence is homologous with the active site of a number of plasma serine proteases including thrombin, factor IXa, factor Xa, and plasmin. These data indicate that bovine factor XII is a precursor to a serine enzyme with an inhibitor sequence and a catalytic site located in the same single polypeptide chain.
...
PMID:Isolation and characterization of bovine factor XII (Hageman factor). 86 Dec 10

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.
...
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.
...
PMID:Studies on the blood clotting and fibrinolytic system in the plasma from a sei (baleen) whale. 96 76

A number of novel aromatic Tris-amidines have been synthesized and investigated for their antiproteolytic property. The basic structure of the compounds is that of mesitylene where each of the methyl groups has been substituted with a 3- or 4-amidinophenoxy moiety. The compounds displayed considerable activity against trypsin (EC 3.4.21.4) and thrombin (EC 3.4.21.5), but proved most effective against porcine pancreatic kallikrein (EC 3.4.21.8). With this enzyme a Ki value of 2.43-10(-8) M was recorded for alpha,alpha',alpha''-tris(4-amidino-2-bromophenoxy)mesitylene at pH 8.1 and 37 degrees C. The most potent thrombin inhibitor, alpha,alpha',alpha''-tris(3-amidinophenoxy)mesitylene, had a Ki value of 6.51-10(-7) M and was also a strong overall anticoagulant. The inhibitors were able to interfere with the kinin release by human plasma kallikrein at concentrations as low as 1-10(-10) M. However, despite this remarkable antikallikrein effect and the known importance of plasma kallikrein in the activation of Hageman factor (factor XII), the compounds had only little influence on the early stages of blood coagulation.
...
PMID:Aromatic Tris-amidines. A new class of highly active inhibitors of trypsin-like proteases. 108 99

The patient described had paroxysmal nocturnal hemoglobinuria associated with recurrent arterial as well as venous thrombosis. Study of platelet function revealed hypersensitivity to epinephrine, adenosine 5'phosphate (ADP) and collagen as judged by their ability to aggregate platelets as well as to release 14C serotonin. The release of total nucleotides was also markedly increased over normal with all aggregating agents. The abnormality was localized to the platelet since aggregation occurred when the patient's platelets were resuspended in normal plasma but not when normal platelets were incubated in the patient's plasma. Presumptive evidence for ongoing intravascular coagulation was an increase in fibrinogen derivatives of heavier molecular weight than the native protein presumably a result of thrombin action. However, factor XII was not activated and fibrinolysis was not increased. Complement component levels and antithrombin concentrations were also normal. The findings in this case suggest that hypersensitive platelets may contribute to the intravascular coagulation that is manifested by the increased incidence of thrombosis in patients with paroxysmal nocturnal hemoglobinuria.
...
PMID:Platelet hypersensitivity and intravascular coagulation in paroxysmal nocturnal hemoglobinuria. 119 Feb 56

Blood coagulation may be activated by the extrinsic or intrinsic pathways. The extrinsic clotting system is put into action by tissue thromboplastin, originating from injured tissue cells, but also from damaged leukocytes and erythrocytes. Tissue thromboplastin is a phospholipoprotein with an enzymatic component, capable of converting the clotting factor VII to its activated form, factor VIIa, which in turn activates factor X. The factor Xa-complex (containing also factor Va, phospholipid, and calcium) is the prothrombinconverting principle. The intrinsic clotting system is based on factors which are contained in the circulating blood. Its activation requires the availability of phospholipid and of activated factor XII (factor XIIa), or factor XIa. Factor XII is activated by collagen, i.e., whenever the vascular endothelium is injured, and to a lesser extent also by "activated" blood platelets. Platelets in turn are activated primarily by thrombin, collagen, and, in a self-perpetuating process, since all these materials are released from activated platelets, also by adenosine-5-diphosphate, adrenaline, and serotonin. The activation of platelets leads to a variety of morphological and biochemical alterations, culminating in their aggregation and in the selective release from storage organelles of different substances, among them those mentioned above. Of particular importance is the fact that in the course of platelet alterations, procoagulant phospholipid also becomes available on the platelet surface. The significance of the activation of the intrinsic system is seen in the possibility of the initiation of a self-sustained process which, after a primary event, e.g. vascular or cellular injury, will continue to convert prothrombin into thrombin. The effects of endotoxin on the blood clotting system show striking species differences. In the rabbit, endotoxin, with the involvement of factors of the complement system, will directly act upon blood platelets and thus initiate intravascular, intrinsic coagulation. In man, endotoxin remains without a direct effect on platelets and alternative possibilities of initiating thrombin formation must be considered. One possibility is extrinsic activation via tissue thromboplastin from injured leukocytes. Another pathway, which is supported by several experimental findings, starts out with endotoxin-mediated endothelial damage. Endothelial cells are in fact severely affected by endotoxin and may even be removed from the vascular wall, thus making accessible the subendothelial activator of factor XII. Thrombin in turn affects the vascular endothelium: therefore, one initiated, the process of intravascular activation of coagulation will perpetuate, this the more as platelets in turn will be stimulated into activity. The possible intervention of other vasoactive factors must also be considered...
...
PMID:[Activation of the blood coagulation system during gram-negative infections and endotoxemias]. 122 91

In the PRP of anaphylactic rats, ADP, collagen and thrombin induced platelet aggregation was considerably reduced. Reduced aggregability could be transferred to normal platelets by suspending them in the PPP of anaphylactic animals and the impaired aggregation of platelets from animals undergoing anaphylaxis could be restored by exchanging their plasma for that of normal controls. Ellagic acid, a known activator of factor XII, produced similar alterations as obtained in anaphylactic shcok. It is suggested that the inhibition of platelet aggregation is due to the anaphylactic activation of factor XII and this mechanism may be of importance in rat anaphylaxis.
...
PMID:Reduced aggregability of platelets in rat anaphylaxis. 126 97


1 2 3 4 5 6 7 8 9 10 Next >>

---