RVV
1. FX ———-> FXa
Ca+2
2. Chromogenic substrate ———-> Peptide + pNA (color)
FXa
The method is based on a two-stage principle. In stage one, Factor X is activated in the presence of calcium to Factor Xa (FXa) by the activator Russell’s Viper Venom (RVV). In stage two, the generated FXa hydrolyses the chromogenic substrate, thus liberating the chromophoric group, pNA. The color is then read with a spectrophotometer at 405 nm. The generated FXa and thus the intensity of color is proportional top the FX activity in the sample.