Search results
Results from the WOW.Com Content Network
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The process of coagulation involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of ...
To produce thrombin, the prothrombinase complex cleaves two peptide bonds in prothrombin, one after Arg 271 and the other after Arg 320. [1] Although it has been shown that factor Xa can activate prothrombin when unassociated with the prothrombinase complex, the rate of thrombin formation is severely decreased under such circumstances.
Therefore, although the coagulation cascade can be triggered in vitro through the intrinsic pathway only, in vivo coagulation is triggered by the extrinsic pathway. However, the model better describing how coagulation works is the so-called cell-based model, a more integrated picture of the whole process, in which phospholipid surfaces, such as ...
Blood coagulation pathways in vivo showing the central role played by thrombin. Factor Xa is the activated form of the coagulation factor X, also known as thrombokinase. Factor X is an enzyme, a serine endopeptidase, which plays a key role at several stages of the coagulation system. Factor X is synthesized in the liver.
This measures the quality of the extrinsic pathway (as well as the common pathway) of coagulation. The speed of the extrinsic pathway is greatly affected by levels of functional factor VII in the body. Factor VII has a short half-life and the carboxylation of its glutamate residues requires vitamin K.
HMWK is one of four proteins which interact to initiate the contact activation pathway (also called the intrinsic pathway) of coagulation: the other three are Factor XII, Factor XI and prekallikrein. HMWK is not enzymatically active, and functions only as a cofactor for the activation of kallikrein and factor XII. It is also necessary for the ...
Thrombin (Factor IIa) (EC 3.4.21.5, fibrose, thrombase, thrombofort, topical, thrombin-C, tropostasin, activated blood-coagulation factor II, E thrombin, beta-thrombin, gamma-thrombin) is a serine protease, that converts fibrinogen into strands of insoluble fibrin, as well as catalyzing many other coagulation-related reactions.
Factor XI (FXI) is produced by the liver and circulates as a homo-dimer in its inactive form. [9] The plasma half-life of FXI is approximately 52 hours. The zymogen factor is activated into factor XIa by factor XIIa (FXIIa), thrombin, and FXIa itself; due to its activation by FXIIa, FXI is a member of the "contact pathway" (which includes HMWK, prekallikrein, factor XII, factor XI, and factor IX).