The isoelectric point of thrombin and its behaviour compared to prothrombin at some solid surfaces.

We have shown that the isoelectric point of thrombin is high and that thrombin is a cation at the pH of blood. On the other hand, prothrombin has a low isoelectric point, being more anionic at the pH of blood. It was also found that thrombin adsorbs readily to surfaces, especially negatively charged surfaces, like behenic acid surfaces at pH 8.2. Furthermore, thrombin adsorbed onto behenic acid was active in the sense that it coagulated fibrinogen. The significance of the electric charge of the thrombin molecule in the mechanism of atherosclerosis is discussed.