Аннотация:1. A procedure for partial purification of human C'1 is described. 2. Under certain conditions of pH, ionic strength, and temperature, partially purified C'1 loses its hemolytic activity and gains complement-inactivating and esterase properties. This preparation is designated “converted C'1”. 3. Complement - inactivating activity of “converted C'1′”is directed primarily against C'4; esterase activity is demonstrable using TAMe as substrate. 4. A correlation exists between disappearance of hemolytically active C'1 during “conversion'reaction and the parallel appearance of complement-inactivating and esterase properties. 5. The possible role of C'1 as a pro-esterase is discussed.
