Summary
We have discovered and charact enzed a novel coagulation
factor Xa inhibitor from the salivary gland of the black fly, Simulium vittatum. Salivary
glands were surgically dissected from the flies and a crude salivary gland extract
was tested for inhibition of a number of coagulation assays. The gland extract inhibited
both thrombin and factor Xa. Tic purify further the factor Xa inhibitor, a factor
Xa affinity column was utilized. Final purification of the black fly factor Xa inhibitor
was achieved by reverse-phase C8 microbore high pressure liquid chromatography. Inhibition
of factor Xa was nearly stoichiometric by the purified inhibitor with no inhibitor
of thrombin detected. SDSpolyacrylamide gel electrophoresis indicated the inhibitor
had a molecular weight of 18,000 and sequence analysis of the inhibitor revealed a
blocked amino terminus. These data indicate that the blood-sucking black fly has evolved
a highly potent inhibitor of mammalian coagulation factor Xa to disrupt its host normal
hemostatic clotting mechanisms.
