Effects of temperature, pH, and inhibitors on the procoagulant characterization of FIa, a factor X activator from the venom of Daboia russellii siamensis (Myanmar)

Abstract

FIa, a factor X activator, was isolated from the venom of Daboia russellii siamensis (Myanmar) after a series of chromatographic separations. FIa displayed procoagulant activity by shortening plasma recalcification time and converted human factor X (FX) to activated human factor X (FXa) by cleaving the heavy FX chain, possibly at the Arg51-Ile52 peptide. FIa was positive in a glycoprotein staining test, demonstrating that it is a glycoprotein. Optimal temperature and pH values were important for FIa procoagulant activity. Procoagulant activity was maintained above 85% of the initial activity at pH 7.0 approximately 8.0, and showed equally maximum activity at temperatures ranging from 30 to 50 degrees C. In addition, FIa procoagulant activity was completely inhibited by EDTA (5 mM), but not by PMSF (10 mM), suggesting that it is a metalloproteinase.