Serrapeptase, a proteolytic enzyme, has been used for the adjuvant treatment of many diseases. However, its fibrinolytic activity is still uncertain. Herein, serrapeptase and in vitro thrombolytic effects were investigated. The results showed that was 1295 U/mg, specific 3867 U/mg protein when toward casein 2800 U/mg. optimum temperature pH 37-40°C 9.0, respectively. At 1 mmol/L, Zn2+, Mn2+ Fe2...