The use of prothrombin activating snake venoms to measure human prethrombin 2: absence of prethrombin 2 in serum.

The activation of the prothrombin intermediate, Prethrombin 2, has been studied in order to establish test systems that would enable identification of Prethrombin 2 in serum and Factor IX concentrates. While activation of Prethrombin 2 by Taipan Snake Venom (TSV) was slow and incomplete, inclusion of approximately molar amounts of prothrombin fragments F1 or F1.2 markedly enhanced the amount of thrombin formed by TSV. This effect could also be obtained by the inclusion of serum. Neither normal serum nor Factor V deficient serum contain any identifiable Prethrombin 2. On the other hand substantial amounts of Prethrombin 2 are present in Factor IX concentrates used for the treatment of Christmas Disease (Hemophilia B).