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° C, Archibald measurements indicate the molecular weight of urokinase to be 53,000.