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A bacterium, producing a fibrinolytic enzyme, was screened from a decaying rice plant. The bacterium was identified as Bacillus subtilis by morphological, biochemical, and physiological properties and named Bacillus subtilis BK-17. The fibrinolytic enzyme (BK) was purified from supernatant of Bacillus subtilis BK-17 culture broth. The molecular weight was 31 kDa as determined by SDS-PAGE. The effect of temperature, pH, and plasminogen on the activity of the bacillokinase (BK) was analysed and the activity was compared with urokinase. The optimal temperature and pH were 50℃ and pH 7, pH 8, respectively. The BK activity was inhibited to 45%, 35%, and 23% with lmM EDTA, Zn^(2+), and Ca^(2+), respectively. However, Mg^(2+), Mn^(2+), and Co^(2+) ions did not have any significant effect on the enzyme activity. The BK showed the activity in the both plates, plasminogen-free fibrin plate and plasminogen-rich fibrin plate. The result indicates that the BK can directly act the fibrin. In comparison of fibrinolytic activity with urokinase on the fibrin plate, the BK shows about 20 folds higher activity than that of the urokinase.
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