Thromboplastin and Platelet Factor 3: Protein and Phospholipid Components Required for Procoagulant Activity

Characteristics of bovine brain and lung thromboplastins and platelet factor 3 are compared, emphasizing protein and phospholipid moieties involved in procoagulant activity. Isolated tissue and platelet procoagulant lipoproteins were separated into lipid and protein fractions by repeated ethanolic extraction. Lipid composition and quantitation was ascertained by thin layer chromatography. The protein-free lipid mixture functioned as a partial thromboplastin. Protein fractions were purified by deoxycholate solubilization, gel filtration, and chromatography on diethylaminoethyl cellulose. Comparative biochemical properties were determined by gel filtration, Polyacrylamide gel electrophoresis, sedimentation velocity and by carbohydrate and amino acid composition. Purified protein components were devoid of enzymatic activity. They were also free of procoagulant activity on prothrombin or au top roth rombin III (Factor X) unless they were combined with one or more phosphatides of ethanolamine (PE), choline (PC), serine (PS), or inositol (PI). The proteins of thromboplastin appear to have homologous biochemical characteristics and phospholipid requirements for expression of proeoagulant activity, while differences in platelet factor 3 activity relate to differences in both protein and phospholipid requirements.

(Supported by USPHS, NIH Grant HL 14142).