Anticoagulant protein which binds to the gamma-carboxyglutamic acid-domain regions of factors IX (F9) and factor X (F10) in the presence of calcium with a 1 to 1 stoichiometry. Also inhibits platelet aggregation by binding to platelet glycoprotein Ibalpha (GP1BA) and functioning as a blocker of von Willebrand factor (VWF). Is devoid of hemorrhagic and lethal activities. Possess antithrombotic and thrombolytic activities. Also hydrolyzes the Aalpha-chain of fibrinogen (FGA). Does not affect the Bbeta-chain (FGB) and the gamma chain (FGG).