Observations on a Pro-esterase Associated with Partially Purified First Component of Human Complement (C'1).

Abstract

A procedure for partial purification of human C''l is described. Under certain conditions of pH, ionic strength, and temperature, partially purified C''l loses its hemolytic activity and gains complement-inactivating and esterase properties. This preparation is designated "converted C''l". Complement-inactivating activity of "converted C''l" is directed primarily against C''4; esterase activity is demonstrable using p-toluene-sulfonyl-L-arginine methyl ester (TAMe) as substrate. A correlation exists between disappearance of hemolytically active C''l during "conversion" reaction and the parallel appearance of complement-inactivating and esterase properties. The possible role of C''l as a pro-esterase is discussed.