Objective: To purify and characterize a novel factor Ⅹ activator

FⅤe-1 from Daboia russelli siamensis (Myanmar) venom. Methods: Methods: FⅤe-1 was purified from Daboia russelli siamensis (Myanmar) venom by ion-exchange chromatography on CM-Sephadex C-50

and gel filtration on SuperdexTM 75 column.The hemostatic activity of FⅤe-1 was determined based on chromogenic substrates. The fibrinogen-clotting activity of FⅤe-1 was also determined. Thermal stability

PH stability

enzyme activity

and inhibition of FⅤe-1 were determined by its remaining procoagulant activity. N-teminal sequence was determined by the method of automated Edman degradation. Results: FⅤe-1 was achieved by chromatography with a molecular weight of 13

808 and an isoelectric point of 4.6. The hemostatic activity of 0.5 mg FⅤe-1 was equal to that of 1.5625 u thrombin or that of 54.93ng RVVⅩ. FⅤe-1 primarily activated FⅩ

however

had no effect on prothrombin and fibrinogen. The suitable pH and temperature range of FⅤe-1 was 6.5-7.5 and 25-60℃

respectively. The activity of FⅤe-1 was enhanced by Ca2+ ion and inhibited by EDTA and DTT. The N-terminal sequence was NH2-N-L-Y-Q-F-G-E-M-I-N. Conclusion: FⅤe-1 is a factor X-activating enzyme

which could activate FⅩ to FⅩa

but have minimal effect on prothrombin and fibrinogen.