Experimental Factor Ontology identifier EFO_0004633 (protein C measurement) is is a quantification of Protein C, also known as autoprothrombin IIA and blood coagulation factor XIV,] is a zymogenic (inactive) protein, the activated form of which plays an important role in regulating blood clotting, inflammation, cell death and maintaining the permeability of blood vessel walls in humans and other animals. Also known as: coagulation factor XIV.