prothrombin


prothrombin
/proh throm"bin/, n. Biochem.
a plasma protein involved in blood coagulation that on activation by factors in the plasma is converted to thrombin. Also called thrombogen.
[1895-1900; PRO-1 + THROMBIN]

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Carbohydrate-protein compound in plasma essential to coagulation.

In response to bleeding, a complex series of clotting-factor interactions leads to its conversion by thromboplastin to thrombin, which transforms fibrinogen in plasma into fibrin. Fibrin and platelets combine to form a clot. Hemophilia is caused by a hereditary lack of one of the clotting factors. Vitamin K is needed to synthesize prothrombin, so conditions that impair the vitamin's absorption result in prothrombin deficiency and a tendency to prolonged bleeding.

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 glycoprotein (carbohydrate-protein compound) occurring in blood plasma and an essential component of the blood-clotting (coagulation) mechanism. Prothrombin is transformed into thrombin by a clotting factor known as factor X or prothrombinase; thrombin then acts to transform fibrinogen, also present in plasma, into fibrin, which, in combination with platelets from the blood, forms a clot (a process called coagulation). Under normal circumstances, prothrombin is changed into thrombin only when injury occurs to the tissues or circulatory system or both; therefore, fibrin and blood clots are not formed except in response to bleeding.

      Hypoprothrombinemia, a deficiency in prothrombin, is characterized by a tendency to prolonged bleeding. It is usually associated with a lack of vitamin K, which is necessary for the synthesis of prothrombin in the liver cells. In adults the condition occurs most commonly in cases of obstructive jaundice, in which the flow of bile to the bowel is interrupted—bile being necessary for the intestinal absorption of vitamin K. It can also result from a general impairment in liver and intestinal-cell function or overdose of warfarin and related therapeutic anticoagulants (anticoagulant).

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Universalium. 2010.

Look at other dictionaries:

  • Prothrombin — is a coagulation (clotting) factor. It is needed for the normal clotting of blood. There is a cascade of biochemical events that leads to the formation of the final clot. In this cascade, prothrombin is a precursor to thrombin. Because… …   Medical dictionary

  • prothrombin — prothrombin. См. фактор II свертывания крови. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Prothrombīn — Prothrombīn, s. Fibrin …   Meyers Großes Konversations-Lexikon

  • Prothrombin — ⇒ Thrombin …   Deutsch wörterbuch der biologie

  • prothrombin — [prōthräm′bin] n. [ PRO 1 + THROMBIN] a factor in the blood plasma that combines with calcium to form thrombin during blood clotting: it is a precursor of thrombin and is synthesized by the liver in the presence of vitamin K …   English World dictionary

  • Prothrombin — Thrombin Oberflächenmodell nach PDB  …   Deutsch Wikipedia

  • Prothrombin — Pro|throm|bin [↑ pro u. ↑ Thrombin] Syn.: Thrombogen, Faktor II: in der Leber gebildetes Glykoprotein vom MG 72 000, das unter Einwirkung verschiedener Blutgerinnungsfaktoren zum Gerinnungsenzym Thrombin abgebaut wird. * * * Prothrombin,   im… …   Universal-Lexikon

  • prothrombin — protrombinas statusas T sritis chemija apibrėžtis Trombino pirmtakas, kraujo plazmos baltymas. atitikmenys: angl. prothrombin rus. протромбин …   Chemijos terminų aiškinamasis žodynas

  • prothrombin — trombinas statusas T sritis ekologija ir aplinkotyra apibrėžtis Hidrolazių klasės fermentas – kraujo krešėjimo reakcijos fermentas, fibrinogeną verčiantis fibrinu. atitikmenys: angl. prothrombin; thrombin; thrombosin vok. Thrombin, n;… …   Ekologijos terminų aiškinamasis žodynas

  • prothrombin — noun Etymology: International Scientific Vocabulary Date: 1898 a plasma protein produced in the liver in the presence of vitamin K and converted into thrombin in the clotting of blood …   New Collegiate Dictionary


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