CRYSTALLINE HUMAN UROKINASE: SOME PROPERTIES.

Human urokinase, an enzyme which activates plasminogen, has been crystallized. Repeated recrystallization yielded preparations of maximum specific activity; such preparations revealed only one component when subjected to polyacrylamide gel disc electrophoresis. Studies with the ultracentrifuge demonstrated that urokinase undergoes a concentration-dependent reversible association at pH 6.8. When the partial specific volume of the enzyme is assumed to be 0.735 milliliters per gram at 10 degrees C, Archibald measurements indicate the molecular weight of urokinase to be 53,000.