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Related to thrombin: antithrombin, Thrombin time


see blood clottingblood clotting,
process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood vessel openings.
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an enzyme of the hydrolase class, a major element in the blood-clotting system of man and animals. It is present in blood in the form of the inactive precursor prothrombin and is activated by prothrombinase, or active thromboplastin. Chemically, thrombin is a glycoprotein with a molecular weight of about 40,000; it contains about 5 percent carbohydrate.

Thrombin was isolated in crystalline form in 1972 by the American physiologist W. Seegers and his associates. It is similar in primary and tertiary structure to the serine proteolytic enzymes such as trypsin. A thrombin molecule consists of two polypeptide chains linked by a disulfide bond. The A chain of bovine thrombin contains 49 amino acid radicals, and the B chain, 265 radicals. The active center of the enzyme, as well as the carbohydrate constituent, are located in the B chain. Thrombin exists in several active forms, which differ in the structure of the B chain.

The main function of thrombin is to convert fibrinogen into fibrin. Thrombin hydrolyzes four arginyl-glycine bonds in the fibrinogen molecule. Four peptides then split off to form a fibrin monomer, which becomes polymerized into the fibrin clot that is the basis of a thrombus. The reactions of limited proteolysis with the participation of thrombin are accompanied by the activation of Factor XIII (fibrin stabilizing factor) and of Factors V and VIII, which take part in the reactions of the internal blood-clotting mechanism. Thrombin aids in platelet aggregation and in clot retraction. A relative excess of thrombin in the body has been shown to automatically initiate the activity of the anticoagu-lating system. This is accompanied by the introduction of heparin and the activator of plasminogen into the bloodstream, substances that help maintain the blood’s liquid state.

Thrombin is inactivated by diisopropyl fluorophosphate, which blocks the hydroxyl group of serine that enters the active center, and by other inhibitors characteristic of the serine proteinase group. Thrombin is inactivated in blood by the plasma antithrombins α2-macroglobulin, antithrombin III, and/or heparin. A specific nonplasma thrombin inhibitor is the polypeptide hirudin, found in the buccal glands of leeches.

Thrombin is used to arrest capillary bleeding by the application of fibrin foam soaked in thrombin to the affected surface.


Magnusson, S. “Thrombin and Prothrombin.” In The Enzymes, 3rd ed., vol. 3. New York–London, 1971.
“A New Thrombin: Purification, Aminoacid Composition, and Crystallization.” Thrombosis Research, 1972, vol. 1, p. 533.



An enzyme elaborated from prothrombin in shed blood which induces clotting by converting fibrinogen to fibrin.
References in periodicals archive ?
As the only topical hemostat from recombinant DNA origin approved in the United States and Canada, Recothrom can be used in pediatric and adult patients with or without antibodies to bovine-derived thrombin.
The clinical use and immunologic impact of thrombin in surgery.
Percutaneous thrombin is increasingly being used and considered a standard option in treatment of pseudoaneurysm.
Thrombin generation was evaluated by sampling the clotting mixture at regular time intervals into a test tube containing fibrinogen.
The importance of thrombin as a key promoter of atherosclerosis has only been shown in animal models [9, 10].
Thrombin is a spray or syringe, and is often used with gelatin foam (Thrombi-Gel) or matrix (FloSeal) (Biologies 2008;2:593-9).
The current assay methods use citrated plasma and are based on inhibition of bovine thrombin or Xa.
When the particles encounter thrombin, the thrombin cleaves the peptides at a specific location, releasing fragments that are then excreted in the animals' urine.
10 mm) is a relative contra-indication for thrombin injection because of a slightly higher risk of distal embolisation.
3) Direct thrombin inhibitors (Parenteral): These drugs are especially useful in cases of heparin induced thrombocytopenia (HIT).
To our mind, a study on prothrombin time, thrombin clotting time and number of platelets aiming at assessment of blood clotting mechanisms and stages can facilitate diagnosis and surgical treatment of oil and gas facility workmen.