Some Biochemical and Electrophoretic Studies on Purified Prothrombin, Factor VII (Proconvertin) and Factor X (Stuart)

1. Complete separation of prothrombin, factors VII and X has been achieved by conventional fractionation technic followed by starch gel electrophoresis.

2. The glycoprotein nature of bovine prothrombin has been confirmed.

3. In addition to hexose and hexosamine, substantial quantities of a hitherto unrecognized constituent, neuraminic acid, have been demonstrated. When included with the other carbohydrates, the total sugars comprise a substantial fraction of prothrombin.

4. In electrophoretic mobility the preponderance of proteins and total neuraminic acid correlate closely with the biologic prothrombin activity.

5. Scission of neuraminic acid by neuraminidase does not result in destruction of the prothrombin, which can subsequently still be converted to thrombin.

6. Significant quantities of neuraminic acid are also found in preparations rich in factors VII and X but devoid of prothrombin. These fractions are relatively low in protein. Here, too, cleavage of neuraminic acid does not destroy biologic activity.

7. Treatment with neuraminidase results in some changes in electrophoretic mobility of some of the protein, resulting in the appearance of a slower moving protein fraction devoid of biologic activity. The mobility of factor VII was slightly altered, but that of factor X remained unchanged.