Heparin-Binding Property of Human Protein C

Abstract

Heparin is well known to interact with various proteins in human plasma [1] which include most of the regulators of coagulation and fibrinolysis such as antithrombin III, heparin cofactor II, protein C inhibitor (PCI), histidine-rich glycoprotein, vitronectin and thrombospondin, and coagulation factors such as factor IX, factor XI, factor XII, prekallikrein, kininogen, fibrinogen, von Willebrand factor and fibronectin. Protein C is the zymogen form of a vitamin K-dependent serine protease present in plasma [2]. Protein C is composed of two chains: the light-chain consists of γ-carboxyglutamic acid (Gla) domain and two epidermal growth factor-like (EGF) domains, and the heavy-chain consists of activation peptide and catalytic domain [3]. It is activated by a thrombin-thrombomodulin complex on the endothelial cell surface and activated protein C (APC), in conjunction with protein S, functions as a regulator of coagulation and also as a stimulator of fibrinolysis [4].