Chapter 9B Inhibitors: protein C

Abstract

This chapter highlights protein C, its structure, function, and mode of activation. In the anticoagulant protein C system, interactions between proteins and cells, primarily endothelial cells, are important and resemble those that occur between certain clotting factors and platelets. Protein C has only been purified from bovine and human plasma. In all purification procedures, inhibitors of proteolytic enzymes, such as diisopropylphosphofluoridate (DFP) and benzamidine are used to minimize the proteolytic degradation of protein C. The plasma concentration of bovine and human protein C is about 4–5 mg/l and the recoveries for the different purification procedures vary between 20% and 30%. Bovine protein C is a glycoprotein with an apparent molecular weight of 56,000-58,000, as judged by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Protein C is first shown to be activated to a serine protease by incubation with trypsin, after which [ 3 H]DFP is incorporated in its heavy chain. The activation peptides from human and bovine protein C show little sequence similarity except that both have several negatively charged amino acids.