Biochemical Studies on the Fibrinolytic Activity of Hemolytic Streptococci I. Isolation and Characterization of Fibrinolysin

The fibrinolytic activity of hemolytic streptococci designates the capacity of cultures of the organisms to liquefy rapidly human fibrin clot (1). The lyric action is referable to the presence in the culture of an extracellular substance, characteristically elaborated by those strains of hemolytic streptococci which are derived from patients suffering with acute streptococcus infections. Investigation of the phenomenon has included studies concerning the mechanism involved in the reaction and consideration of a possible relationship to the more general problem of infection and resistance (2). The biochemical studies to be described in this and the succeeding communication deal with two aspects of the phenomenon. This report is concerned with the isolation and characterization of the active fibrinolytic principle elaborated by the organisms. Methods are described by which the lytic substance may be removed from culture filtrates, concentrated, and partially purified. Some of the physical properties of the active preparations are described. The second paper (3) deals with the biochemical action of the lyric substance and the nature of the end-products. The phenomenon of fibrinolysis induced by the bacterial agent consists of a rapid change of fibrin from its solid clotted form to a soluble substance. The transformation, therefore, as it occurs in vitro, is readily visible, since the coagulated gel is not disturbed by inversion of the test tubes and the process of liquefaction converts the