Determination and properties of the fibrinolysis accelerating substance (FAS) in Japanese fermented soybean "natto"

Using trypsin-fibrin plate method, strong activity of the fibrinolysis acce lerating substance (FAS) was proved in water extract of Japanese fermented soybean "natto". In 7 commercial natto preparations, high concentrations of 74,100 +/- 54,500 units (equivalent to mug surfactin)/100 g wet weight (Me an +/- SD) were detected. FAS strongly accelerated not only the activities of direct fibrin degradating enzymes such as plasmin, trypsin, and earthwor m protease, but also that of the plasminogen activator (urokinase) and pro- urokinase activator (nattokinase). It was easily separated as dark yellow p owder from natto extract by two-step procedures of acid-precipitation (pH 2 .0) and ethanol treatment (soluble fraction). The final yield and purity fr om 1 kg natto were about 817,000 units (dry weight 4.6 g) and 177.6 units/m g, respectively.