Pro-thrombin

a glycoprotein formed and stored in the parenchymal cells of the liver and present in blood in a concentration of approximately 20 mg/100 mL

Description
In the presence of thromboplastin and calcium ion, prothrombin is converted to thrombin, which in turn converts fibrinogen to fibrin, this process resulting in coagulation of blood; a deficiency of pro-thrombin leads to impaired blood coagulation. See pro-thrombin time