Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

By devising and applying quantitative methods for the assay of thrombin and autoprothrombin C and by developing techniques for their purification, it was possible to obtain information about the function and properties of antithrombin. The inhibitor is a protein for which the initial purification steps consist of removing fibrinogen from plasma by heating to 56 degrees for 3 min, removing prothrombin complex by absorption on barium carbonate, absorbing the antithrombin on aluminum hydroxide, and eluting with phosphate buffer. Antithrombin is limited in its capacity to neutralize thrombin activity, and, under some conditions, the rate of inhibition was accelerated, but equivocal results were involved. Heparin cofactor was found to be essential for retarding the formation of thrombin, and, by inference, it is essential for retarding the formation of autoprothrombin C. Heparin cofactor and antithrombin III are the same. Thrombin absorbs on fibrin, and this has been referred to as the "antithrombin I effect." Interference with the thrombin-fibrinogen reaction by mixtures of antithrombin III and heparin is called the "antithrombin II henomenon." The acceleration of thrombin inactivation at the time thrombin forms is called the "antithrombin IV effect." It was discovered that antithrombin III neutralizes thrombin, as well as autoprothrombin C. The inhibitor and the enzyme form a mutual depletion system. To assay for antithrombin III, a standard quantity of thrombin (about 1,100U/ml) was reacted with antithrombin III for 2 hr. The percent thrombin inactivated was then measured. In random samples of human blood, a wide range of antithrombin III concentration was found. The inhibitor is relatively stable in plasma and serum. It is not changed in concentration when Dicumarol therapy is instituted. Ether extraction of plasma reduces antithrombin III activity. Seitz filtration of plasma did not remove activity. Under special conditions, antithrombin III enhances esterase activity of thrombin. Under special conditions, thrombin regenerates from the thrombin-antithrombin III complex. Antithrombin III neutralizes the activity of prethrombin-E and thrombin-E; consequently, an active histidine center found in the B1 chain of thrombin is not essential for the binding of antithrombin. Autoprothrombin II-A activity was neutralized by antithrombin III. Autoprothrombin C was found to be neutralized by antithrombin III; the amounts required varied with the molecular forms of autoprothrombin C. Thrombin and autoprothrombin C apparently occupy the same binding sites on antithrombin III. An equation was developed to account for all the known characteristics of antithrombin III functions. The kinetic aspects of thrombin neutralization were found to correspond exactly with those of autoprothrombin C. Antithrombin III is a high-capacity inhibitor of the two most powerful enzymes in blood coagulation.
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PMID:Antithrombin III: a backward glance o'er travel'd roads. 4 4

Ether precipitation of globulins from the supernatant fraction of prothrombin complex concentrate, followed by adsorption on tricalcium phosphate and elution gives a beta2 fraction termed Bridge anticoagulant neutralizing agent (BANA). Although this is completely free of all known blood clotting factors, it improves recalcification time, PTT and thromboplastin generation of hemophilic plasma. It also counteracts the effect of factor VIII inhibitor. Ultrasonic elution produced more activity per mg N than did citrate elution. The possibility is discussed of incorporating BANA preparation in the routine fractionation of plasms without reduction in the yield of factor VIII or prothrombin comples concentrate.
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PMID:Ultrasonic purification of Bridge anticoagulant neutralizing agent (BANA) and a study on its effect on factor VIII inhibitor. 43 13

It has been possible to duplicate in the hemophilic dog four of the major experiments which have suggested in humans an "anticephalin" hypothesis for the pathogenesis of hemophilia. The experiments in the dog have been considerably extended, as compared with the human experiments, by a variety of techniques. I. Asbestos was placed in contact with hemophilic dog plasma, and the clotting time became shorter. When transfused, this plasma had no effect on the defective prothrombin utilization of hemophilic dogs, in contrast to untreated normal plasma. II. The ionic strength of native dog plasma and dog plasma citrated (38 per cent sodium citrate) then recalcified (0.2 M CaCl(2)) were calculated. The ionic strength of the native plasma was approximately 0.15 while that of the citrated plasma was approximately 0.21. Conductivity and freezing point determinations on the plasmas described above were consistent with the idea that the ionic strength of the citrated plasma was significantly higher. The biphasic dilution curve, to which much significance has been attached in arriving at the "anticephalin" hypothesis, can be produced readily in the dog. Diluting dog plasma with "iso-ionic" or "hyper-ionic" NaCl solution abolished the biphasic phenomenon. Dilution with distilled water exaggerated the biphasic curve. These experiments suggest that the biphasic curve is an artifact of uncontrolled ionic strength. III. The prothrombin utilization rates of undiluted whole hemophilic dog blood and hemophilic dog blood diluted 1:2 with 0.85 per cent NaCl were found to be the same. IV. Ether extraction of both normal and hemophilic dog plasma removed fibrinogen and reduced somewhat the concentration of prothrombin. In treated normal plasma AHF was reduced to the level of untreated hemophilic plasma, thus producing a quasi-hemophilic plasma. Defibrination and ether extraction of both normal and hemophilic dog plasma "generated" clotting activity which shortened the clotting time of hemophilic plasma and was active in the thromboplastin generation test. The activity "generated" by defibrination and ether extraction of dog plasma was adsorbed by a BaSO(4) suspension and shown, therefore, not to be the anti-hemophilic factor (AHF). Transfusion of ether-extracted normal or hemophilic dog plasma into hemophilic dogs had no effect on the prothrombin utilization rate, unlike untreated normal plasma which had a marked effect. Thus, four of the main lines of evidence supporting the "anticephalin" hypothesis were duplicated in the dog. However, by extending the experiments it was found that all were explainable on bases other than the presence of "anticephalin." Such an hypothesis is not necessary, therefore, to explain the pathogenesis of canine hemophilia. The apparent identity of hemophilia in the two species suggests that the hypothesis is also not applicable to humans.
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PMID:The pathogenesis of hemophilia; an experimental analysis of the anticephalin hypothesis in hemophilic dogs. 1344 37