Which of the following is not a naturally occurring anticoagulant in the body?

Antithrombin 3 is a circulating protease inhibitor that binds to serine proteases blocking their activity as a clotting factor. Activated protein c along with cofactor protein s inactivates factors 5 and 8 and inactivates inhibitors of tissue plasminogen activator increasing formation of plasmin.Von Willebrand factor helps in platelet aggregationRef: Ganong&;s Review of medical physiology, 24th edition.Pg no.78,566