Hydrolyzes fibrin. Activated by Mg(2+) and Fe(2+) ions. Inhibited by Cu(2+) ions and EDTA. Activity is unaffected by Ca(2+), Ba(2+), Zn(2+), K(+) and Mn(2+) ions. Optimum pH is 6.0. Active from pH 5.0 to 8.0 at 37 degrees Celsius, above pH 8.0 stability decreases rapidly. Optimum temperature is 25 degrees Celsius. Active between 15 and 45 degrees Celsius, however activity rapidly decreases after 1 hour incubation at temperatures above 40 degrees Celsius. Belongs to the peptidase S1 family.