Biochemistry, Antithrombin III

Excerpt

Antithrombin is a plasma glycoprotein consisting of 432 amino acid residues integral in the regulation of the coagulation process during bleeding. Antithrombin most notably binds to serine proteases factor II (thrombin), factor IXa, and factor Xa which inhibits the blood clotting process involved in the coagulation cascade pathway. As part of the normal physiological response to bleeding, platelets circulating the plasma become initially activated by multiple factors produced from endothelial cells to aggregate and form a plug. Circulating fibrinogen is then converted into fibrin by thrombin through a series of protease activations, which constitute the reactions of the coagulation cascade pathway. Fibrin acts to stabilize the initial platelet-created plug which determines the completion of the clot formation.

Antithrombin is among the number of regulatory mechanisms of the coagulation cascade which provides a counter mechanism to clot formation. It serves as up to 80% of the inhibitory component to thrombin formation, as well as factor IXa and factor Xa inhibition. Deficiency in antithrombin has clinical links to increased risks of thrombosis, thromboembolism, and associated complications associated with a hypercoagulable state. This activity aims to provide a generalized understanding of the biochemical properties of anti-thrombin, present an overview of its structure in correlation to its function regarding interactions with serine proteases and heparin.