Abstract
A specific inhibitor for the reaction of the eighth component of guinea pig C was generated in vitro in preparations of partially purified C8 coincidentally with the loss of hemolytic C8 activity during storage at 2°C under conditions of low ionic strength (0.04) at pH 7.5, or after treatment with extremely low concentrations of trypsin. The C8 inhibitor demonstrated physicochemical properties similar to those of hemolytically active C8 in that it was protein in nature, had a sedimentation constant of 7.7 and exhibited extreme lability at 56°C; apparently it was generated from the hemolytically active species of the C8 molecule.
This inhibitor has been called the C8-analogue because it appears to function by competitive binding to and blocking of C7 sites. The reactivities of both hemolytically active C8 and the C8-analogue with the C7 site were influenced in a similar manner by temperature and ionic strength, and the reactions of both were inhibited by Antrypol (Imperial Industries, Ltd., Great Britain). Moreover, EAC7 that had been reacted with the C8-analogue were capable of depleting C9 from the fluid phase of reaction.
