prothrombin
Noun: A protein present in blood plasma that is the inactive precursor (zymogen) of the enzyme thrombin, which is essential for blood clotting. It is synthesized in the liver and requires vitamin K for its production.
Prothrombin is a specific biochemical term used primarily in medical, biological, and clinical contexts to discuss the blood coagulation cascade. - It is often measured via a prothrombin time (PT) test to assess how quickly blood clots. - Its conversion to the active enzyme thrombin is a central step in forming a fibrin clot.
- The doctor ordered a test to check the patient's prothrombin level.
- Vitamin K deficiency can lead to reduced prothrombin synthesis.
- In the coagulation pathway, Factor Xa converts prothrombin into thrombin.
- Prothrombin Time (PT): A common laboratory test that measures the time it takes for plasma to clot after the addition of tissue factor, primarily assessing the extrinsic and common pathways of coagulation which involve prothrombin.
- Prothrombin Complex Concentrate (PCC): A medication containing concentrated clotting factors, including prothrombin, used to reverse the effects of certain blood thinners or treat bleeding disorders.
- Prothrombin Gene Mutation (e.g., G20210A): A genetic variant that can lead to elevated prothrombin levels and an increased risk of abnormal blood clot formation (thrombosis).
- Thrombin (noun): The active serine protease enzyme formed from prothrombin, which converts fibrinogen to fibrin during clot formation.
- Prothrombinase (noun): The enzyme complex (composed of Factor Xa, Factor Va, calcium ions, and phospholipid) that catalyzes the conversion of prothrombin to thrombin.
- Hypoprothrombinemia (noun): A condition characterized by abnormally low levels of prothrombin in the blood.
- Factor II: This is the standard numerical designation for prothrombin within the coagulation factor system.
The term refers exclusively to the specific precursor protein. It does not describe the clotting process itself or the active enzyme (thrombin). Its primary context is the physiology of hemostasis (blood clotting) and related pathologies.
- a protein in blood plasma that is the inactive precursor of thrombin