1. Treatment of crude concentrates of streptokinase with protamine results in removal of about 90 per cent of the nitrogenous material, including nucleic acid and protease inhibitor, with little or no loss of activity.

2. Streptokinase solutions undergo reversible inactivation with changes in pH. The rate and extent of inactivation are dependent on pH, being greatest over a very narrow range about pH 5. The rate and extent of inactivation are also a function of temperature, both increasing with the temperature of incubation. The rate of reactivation is a function of pH and temperature, increasing as either is raised. However, as the temperature is raised above about 23°C., or the pH above about 9, a secondary, irreversible inactivation of streptokinase occurs.

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