Molecular Weights of Human Prothrombin and Thrombin by Electron Irradiation

The enzyme thrombin and its precursor, prothrombin, play central roles in the process of blood coagulation. The availability of purified thrombin and prothrombin has made possible studies of the sizes of these two molecules by ultracentrifugation and other methods (1-5). There is some disagreement among the published figures, and there are little data on human materials. An attempt has been made to estimate the molecular weights of human thrombin and human prothrombin by applying target theory (6). The advantages of this technique are that only small amounts of material are necessary and that, as a rule, the presence of impurities does not affect the molecular weight estimates.