title: Activation of a pro-enzyme by a stoichiometric reaction with another protein. The reaction between prothrombin and staphylocoagulase.
abstract: The reaction between prothrombin and staphylocoagulase was investigated and the following conclusions were drawn: (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 when estimated both by gelfiltration and by sodijm dodecylsulphate-polyacrylamide gel electrophoresis. (c) The amino acid composition of coagulase-thrombin cannot be distinguished from the sum of the amino acid compositions of prothrombin and staphylocoagulasd. (d)in a preparation of coagulase-thrombin the N-terminal amino acids are those of prothrombin (alanin) and staphylocoagulase (aspartic acid). (e) An antibody against coagulase-thrombin precipitates prothrombin and staphylocoagulase but not thrombin. (f) We put forward the hypothesis that the thrombin activity in coagulasethrombin is the result of a stoichiometric reaction between one molecule of prothrombin and one molecule of staphylocoagulase, and limited proteolysis does not play a role in this mechanism.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001777:Blood Coagulation; D003030:Coagulase / Q000276:immunology / Q000378:metabolism*; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D004950:Esterases / Q000378:metabolism; D008970:Molecular Weight; D011516:Prothrombin / Q000276:immunology / Q000378:metabolism*; D013917:Thrombin / Q000276:immunology / Q000378:metabolism
chemical_list: D000596:Amino Acids; D003030:Coagulase; D004792:Enzyme Precursors; D011516:Prothrombin; D004950:Esterases; D013917:Thrombin