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)

Factor VIII (antihemophilic factor) is the protein that is deficient or defective in patients with classical hemophilia and Von Willebrand syndrome. Factor VIII in plasma is thought to be associated in a complex with the highest molecular weight multimers of another glycoprotein, Von Willebrand protein. Highly purified human factor VIII appears to have an Mr of between 200,000 and 300,000 and to consist of several polypeptide chains. The concentration of factor VIII in plasma is around 100-200 ng/ml, equivalent to around 1 nM. The purified proteins retain one or more of the known properties of factor VIII, including the acceleration of factor IXa-mediated activation of factor X, ability to be activated by thrombin and factor Xa, inactivation by activated protein C, and by human antibodies to factor VIII. Among the known clotting factors, factors VIII and V are exceptional in not possessing enzymatic activity. Factors IXa and VIII and X appear to form a functional complex, all of which need to be present and active simultaneously for optimal activation of factor X. The mechanism by which factor VIII promotes activation of factor X by factor IXa is not known, but the major effect is to increase the rate of the reaction. Following treatment of factor VIII with thrombin, a new and smaller polypeptide Mr around 70,000 +/- 5,000 is produced. Factors IXa and Xa also have been reported to activate factor VIII. It is not known whether limited proteolytic cleavage is required absolutely for the expression of factor VIII activity or if it only increases an activity already expressed by the uncleaved protein. Factor VIII is inactivated by thrombin and by activated protein C. Thus, factor VIII can be modulated by at least four of the serine proteases in the clotting system. A major goal for future research is to increase our understanding of the role in blood clotting played by factor VIII, and to apply this information to clinical problems which result from inherited abnormalities of factor VIII.
...
PMID:Factor VIII: structure and function in blood clotting. 642 37

Human factor VIII procoagulant protein (factor VIII) was purified using a modification of our previously described method, in which Sephacryl S-400 elution, rather than QAE-cellulose chromatography, served as the final purification step. The protein had a specific activity of more than 2500 U/mg and consisted of a single polypeptide (Mr 100 000) when analyzed by SDS-polyacrylamide gel electrophoresis. Factor VIII was shown to be a glycoprotein by staining with periodic acid-Schiff's reagent following electrophoresis. Treatment of factor VIII with a mixture of exo- and endoglycosidases caused a reduction by about 50% in the intensity of periodic acid-Schiff staining, as determined by scanning densitometry, and an increase in electrophoretic mobility (equivalent to a new Mr 95 000). Removal of this portion of the total carbohydrate had no significant effect on factor VIII clotting activity or on thrombin potentiation of clotting activity. The in vivo survival curves of a native and sugar-depleted 125I-labeled factor VIII both showed similar patterns of initial rapid decay to 60 and 40% activity, respectively, followed by a one-half decay time of 4 h for both. These results suggest that the carbohydrate portion of human factor VIII does not contribute significantly to either clotting function in vitro or to biological turnover in vivo.
...
PMID:The effect of carbohydrate depletion on procoagulant activity and in vivo survival of highly purified human factor VIII. 643 Mar 52

Fifty batches of Factor VIII concentrates from 12 producers were characterized in a long-term follow-up. The following parameters were measured: Factor VIII: C, Factor VIIIR: AG, Factor VIII: Rcof, specific activity (U Factor VIII: C/mg protein), fibrinogen, IgG, IgM, IgA, isoagglutinins, Hbs-AG, heparin-like activity, thrombin-like activity, antithrombin III, Factor VIII-stability at room temperature, and the rate of complete dissolution of the lyophilizate. In most preparations there was an unacceptable batch-to-batch variation of both Factor VIII complex and contaminating proteins, which exceeded the inter-assay coefficient of variation of the applied test systems. Nevertheless, different brands could be recognized by their typical protein pattern. The results obtained suggest that the standardization of Factor VIII concentrates of unknown composition is still accompanied by considerable risks.
...
PMID:In vitro characterization of commercial Factor VIII concentrates: long-term follow-up. 643 Mar 69

Activated porcine Factor IX is irreversibly inhibited by an active site histidine-directed serine protease inhibitor, dansyl-glutamyl-glycyl-arginyl-chloromethylketone (DEGR-CK). The kinetics of inhibition are second order up to inhibitor concentrations of 10(-5) M. The apparent second-order rate constant (in 0.20 M NaCl, pH 8.0) is 1.7 X 10(4) M-1 min-1, which is considerably lower than values reported for Factor Xa, thrombin, plasmin, and kallikrein. Reaction of increasing concentrations of DEGR-CK with Factor IXa, followed by analysis of residual enzymatic activity, yields 1.2 mol DEGR-CK/mol protein, indicating 1:1 stoichiometry for the DEGR-CK/Factor IXa interaction. DEGR-Factor IXa is a potent anticoagulant in vitro. A concentration of 1 nM causes 50% inhibition of the ability of normal porcine-citrated plasma to correct either Factor VIII- or Factor IX-deficient plasmas (intrinsic pathway factors). In contrast, more than 100 nM DEGR-Factor IXa is required to cause 50% inhibition of Factor VII (extrinsic pathway) or Factor X (common pathway) assays. Activation of porcine Factor VIII:C by thrombin in the presence of DEGR-Factor IXa and phosphatidylcholine-phosphatidylserine vesicles reveals that DEGR-Factor IXa markedly stabilizes the spontaneous loss of Factor VIII:Ca activity as does unmodified Factor IXa [P. Lollar, G.J. Knutson, and D. N. Fass (1984) Blood 63, 1303-1308]. These results suggest that DEGR-Factor IXa incorporates into the intrinsic pathway Factor X-activator enzymatic complex, and also that stabilization of Factor VIII:Ca by this complex is independent of the active site of Factor IXa. Inhibition of Factor IXa by DEGR-CK results in the first reported irreversible active-site-modified derivative of this enzyme. DEGR-CK promises to be a useful reagent in the study of the Factor X activator complex. Conceivably, its specific anticoagulant properties could have future clinical benefit.
...
PMID:Inhibition of activated porcine factor IX by dansyl-glutamyl-glycyl-arginyl-chloromethylketone. 643 27

Previous studies have demonstrated the binding of Factors IX and IXa to cultured bovine aortic endothelial cells. The present study examines the interaction of Factors IX, IXa, and Xa with the luminal surface of calf aortas, shown by microscopic examination to have a continuous layer of endothelium. Radioimmunoassay of Factor IX showed that 74 fmol/10(6) cells of Factor IX could be eluted from freshly prepared aortic segments. Binding of 3H-Factors IX and IXa to aortic segments was saturable, and comparable to binding in previous studies using cultured endothelial cells. Preincubation of aortic segments with 3H-Factor IXa and von Willebrand factor (VWF)/Factor VIII, followed by washing and addition of Factor X, resulted in formation of Factor Xa. The addition of prothrombin to these activation mixtures resulted in formation of thrombin. Exogenous phospholipid and Factor V were not required for Factor X and prothrombin activation on the intact native endothelium. Incubation of 125I-Factor Xa with the vessel segments resulted in most of the tracer being complexed with antithrombin III originally present on the aortic segment (3.8 pmol antithrombin III/10(6) cells). The Factor Xa-antithrombin III complex was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis exclusively in the supernatants. 125I-Factor Xa not complexed with antithrombin III bound specifically to the vessel segment. The time course of binding was biphasic, consisting of an initial more rapid reversible phase followed by a slower irreversible phase. The latter phase correlated with the formation of a covalent complex (Mr, 76,000) between 125I-Factor Xa and a vessel-localized protein presumably distinct from antithrombin III. The activation of prothrombin by vessel-bound Factor Xa was inhibited by anti-bovine Factor V IgG, suggesting that there is interaction of Factor Xa with a Factor V-like molecule provided by the endothelial cell surface. Addition of antibody to antithrombin III prevented formation of Factor Xa-antithrombin III and thrombin-antithrombin III complexes in the supernatant and increased apparent thrombin activity 30-50-fold. These studies demonstrate that freshly obtained vessels with a continuous layer of native endothelium can support activation of Factor X and prothrombin: vessel-bound Factor IXa can activate Factor X in the presence of VWF/Factor VIII. Factor Xa can also bind to the vessel and participate in the activation of prothrombin. The apparent efficiency of prothrombin activation, however, is dampened by the presence of functional antithrombin III on the vessel wall.
...
PMID:A coagulation pathway on bovine aortic segments leading to generation of Factor Xa and thrombin. 643 37

An experimental animal model of disseminated intravascular coagulation (DIC) induced by the co-infusion of coagulant-active phospholipid and activated Factor X (Factor Xa) is described. The infusion of Factor Xa at a dose of 6.6 X 10(-12) mol/kg with phosphatidylcholine/phosphatidylserine (PCPS) lipid vesicles at a dose of 4.0 X 10(-8) mol/kg was associated with significant falls in the levels of fibrinogen and Factors V and VIII, and a bleeding diathesis developed. Assays of Factors V and VIII were performed by a one-stage prothrombin time and activated partial thrombin time system, respectively. In additional experiments, the effect of the same dose combination of Factor Xa/PCPS on Factor V kinetics was studied by preinfusing 125I-labeled Factor V. After Factor Xa/PCPS infusion, Factors VIII and V were reduced at 2 min by 90 and 50% of the preinfusion levels, respectively, and at 1 h by 80 and 75%, respectively. During the same period, there was little change in the total circulating radioactivity. Autoradiography indicated small but detectable levels of circulating proteolytic products of Factor V that comigrated with peptides obtained by the incubation of Factor V with Factor Xa and activated protein C. The majority of radioactivity remained associated with the intact single-chain precursor Factor V. These observations suggested maintenance of the precursor pool after the onset of DIC. This was confirmed by performing two-stage assays of Factors V and VIII, whereby each was completely converted to the active cofactor, i.e., Va and VIII:Ca, by preincubation of the test sample with thrombin before assaying in a one-stage system as before. The Factor V levels assayed by the two-stage procedure did not change appreciably over 1 h. The Factor VIII levels fell but corrected within 1 h at a time when the level measured by a one-stage assay remained depressed. These results indicate that in the dog, infusion of Factor Xa/PCPS induces changes characteristic of DIC, and this is associated with the appearance of Factor V peptides characteristic of the expression of Factor Xa and activated protein C-like activities. The differences noted between the one-stage and two-stage assays suggest that the one-stage assay is measuring the activated fraction of each cofactor and not the total level of the available precursor for each activated species. The results suggest a close correlation between the activated fraction of both cofactors and the hemostatic abnormality that occurs in DIC.
...
PMID:Studies of Factors V and VIII:C in an animal model of disseminated intravascular coagulation. 643 44

Detailed coagulation studies were done prospectively on 43 patients with biliary atresia who had undergone Kasai operation (hepatic portoenterostomy). Patients were divided into three groups based on levels of factor V, factor II, and Echis II and/or response to vitamin K: no coagulopathy (46.5% of patients); coagulopathy of liver disease (30.2% of patients); and coagulopathy of vitamin K deficiency (23.3% of patients). Patients with the coagulopathy of liver disease had significantly lower levels of factors XII, V, and antithrombin III as well as longer thrombin times than patients with no coagulopathy or vitamin K deficiency. Factor V levels were decreased only in patients with more advanced liver disease; normal levels of factor V were not usually helpful in differentiating liver disease and vitamin K deficiency. The prothrombin time, factor VII-X levels, and factor II levels were significantly different for all three groups; the most abnormal values occurred in the vitamin K-deficient group. Comparison of the Echis II level to factor II coagulant activity was helpful in deciding whether a coagulopathy was due to liver disease, vitamin K deficiency, or both. Factor VIII levels were elevated in all groups. Factor VIII coagulant activity was significantly higher by the two-stage (TGT) method than by the one-stage (PTT) method. Hypersplenism causing neutropenia and thrombocytopenia was commonly seen after the age of 5 years. Vitamin E deficiency was more common than vitamin K deficiency; however, all vitamin K-deficient patients were vitamin E deficient. Coagulation status correlated well with hepatobiliary scan data, but not serum bilirubin levels. Recommendations for treatment of patients with vitamin K deficiency and/or liver disease are discussed.
...
PMID:The multiple coagulopathies of biliary atresia. 669 16

Fresh frozen plasma (FFP), was shock-frozen to -25 degrees C within six hours after blood donation. The platelet count was reduced to 20 000/mm3. Aliquots were stored at -20 degrees C and -40 degrees C up to 24 months. Quick, PTT, factor V, VIII, IX, thrombin, antithrombin III, plasminogen, plasma-prekallikrein and kallikrein were determined monthly. With respect to the parameters investigated there was no significant difference between storage at -20 degrees C and -40 degrees C. Factor VIII loss was 10% after 12 months of storage. The activity of factor IX and V remained unchanged during 12 months, then factor V increased during storage. The other parameters did not change. Our study indicates quality of FFP seems not primarily depend on storage temperature, but an optimal preparation technique is much more important.
...
PMID:[Stability of blood coagulation factors in deep frozen fresh plasma by storage at -20 degrees C and -40 degrees C]. 670 85

Factor VIII/von Willebrand factor (vWF) was sought by immunofluorescence in or on canine platelets and blood vessels. None was found on normal canine platelets and little was present in normal canine arteries, veins and capillaries compared with normal human blood vessels. However, free granules of vWF were scattered in platelet-rich canine plasma and occasional granules appeared on small clumps of platelets when ristocetin or collagen was added to the plasma. When the same platelets were suspended in human plasma and ristocetin or collagen was added, more clumps were formed and more vWF (human) was associated with these clumps. When thrombin was added to canine platelets in either canine or human serum, more solid, small clumps of platelets were formed and stained with anti-vWF sera. When thrombin was added to canine platelets in either canine or human plasma, a single large clot was formed which stained brightly for vWF.
...
PMID:Some immunofluorescent observations on factor VIII/von Willebrand factor in dogs. 677 99

Peritoneal fluid does not clot spontaneously on collection, due to a lack of prothrombin activation, consequent upon a virtual absence of factors V and VIII. Factor VIII related antigen is present in peritoneal fluid in only very small amounts, suggesting that this factor is excluded from the peritoneal cavity, probably by virtue of its size. Slight thrombin activity is demonstrated by the presence of fibrin monomers in the fluid. That peritoneal fluid also contains fibrinolytic activity is shown by high levels of plasminogen and plasmin-antiplasmin complexes, though no plasminogen activator could be detected. No differences were found in clotting and fibrinolytic activities, between fluid taken from these patients with, and those without, laparoscopic evidence of pelvic endometriosis.
...
PMID:Clotting and fibrinolytic activities in peritoneal fluid. 677 52


<< Previous 1 2 3 4 5 6 7 8 9 10

---