Abstract
The phospholipases C from Bacillus cereus and Clostridium perfringens showed different affinities for the thromboplastic suspensions used in the one-stage prothrombin time system. In the presence of colistin sulfate the affinities were reversed. In each case one enzyme would further degrade the thromboplastic material following destruction by the other enzyme. The results indicate that a negative zeta potential of the micelles is probably optimal for both clotting activity and susceptibility to B. cereus enzyme, whereas the opposite charge inhibits clotting but renders the substrate more susceptible to C. perfringens enzyme.