The Reaction between Prothombin and Staphylocoagulase

Abstract

The reaction between prothrombin and staphylocoagulase is studied.a. Optimal amounts of the active reaction product (coagulase-thrombin) are found when equimolar amounts of prothrombin and staphylocoagulase are added together.b. The molecular weight of coagulase-thrombin equals the sum of the molecular weights of staphylocoagulase and prothrombin, both when estimated by gelfiltration and by SDS-polyacrylamide gel electrophoresis.c. The amino acid composition of coagulase-thrombin is not in contrast with the sum of the amino acid compositions of staphylocoagulase and prothrombin.d. In a preparation of coagulase-thrombin the N-terminal amino acids are those of prothrombin (alanine) and staphylocoagulase (aspartic acid).e. An antibody against coagulase-thrombin precipitates both prothrombin and staphylocoagulase but not thrombin.f. It is concluded that the thrombin acitivity in coagulase-thrombin is a result from a stoichiometric reaction between one molecule of prothrombin and one molecule of staphylocoagulase and that limited proteolysis does not play a role in this mechanism.