THE COAGULANT ACTION OF CRYSTALLINE TRYPSIN, CEPHALIN AND LUNG EXTRACTS

Abstract

The thromboplastic action of crystalline trypsin is greatly enhanced by Ca and completely inhibited by sufficient excess of citrate. The recognition of this dependence upon Ca makes possible a direct comparison of the enzyme with a major, somewhat unstable, and non-lipid component of plasma prothrombin and aqueous tissue extracts. The exptl. analysis reveals that a "thromboplastic enzyme" may be postulated, which, under ordinary conditions of thrombin formation, contributes to the mobilization of the essential phospholipid factor. Thrombin formation may be conceived as an enzymic mobilization of cephalin and Ca at the colloidal surface of the protein (prothrombin) substrate, with the resulting elaboration of a substance capable of clotting fibrinogen. The postulated amts. of enzyme are too small to evince gross proteolysis, but syneresis, fibrinolysis, and thrombinolysis may be attributed to the feeble digestive powers of the trypsin-like "thromboplastic enzyme.".