Enzymatic inactivation of heparin cofactor II by a proteinase (proteinase-1) isolated from Echis carinatus venom.

Heparin cofactor II was enzymatically inactivated by incubation with Echis carinatus venom in the presence of calcium. The initial rate of inactivation increased proportionately with the addition of heparin to a final concentration of 50 micrograms/ml. A proteinase, termed proteinase-1, was purified 17.5-fold from the venom which also enzymatically inactivated heparin cofactor II in the presence of calcium. The initial rate of heparin cofactor II inactivation by proteinase-1 was not increased by heparin at concentrations as high as 200 micrograms/ml. Heparin cofactor II was not inactivated by either unfractionated venom or proteinase-1 in the absence of calcium. The results indicate that heparin cofactor II, like antithrombin III, is susceptible to enzymatic inactivation by metalloproteinases in snake venoms.