Venom of the ant Pseudomyrmex sp. Further characterization of two factors that affect human complement proteins

Two factors in the venom of the tropical ant Pseudomyrmex sp. had potent anti-complementary activity. The first (F1) was resistant to boiling and had the properties of a polysaccharide or glycoprotein. It had no effect on purified C4 and C2, but caused activation of C1, resulting in the consumption of C4 and C2 in normal human serum. F1 appeared to activate C1 by forming a complex with a nonimmunoglobulin factor in normal human serum. The serum factor was not C1q. The second venom factor (F2) was heatlabile (56°C, 30 min), and was identified as a trypsin-like enzyme. It hydrolyzed α-N-benzoyl-DL-arginine p-nitroanilide HCl and was inhibited by soybean trypsin inhibitor, but not by EDTA. It caused inactivation of purified complement components, but not components in serum, presumably because of natural serum inhibitors. F1 and F2 were closely associated in native ant venom. After gel filtration of the venom, two complement inactivators were eluted. They had m.w. of 175,000 and 32,500 daltons, but F1 and F2 were associated with both m.w. species. F1 and F2 migrated together after electrophoresis on polyacrylamide gels, and both were identified in the ultrafiltrate of ultrafiltration membranes having an m.w. cut-off of 10,000 daltons. The results of this report and previous studies show that ant venom is a potent activator/inactivator of components in both the classical and alternative complement pathways.