Subtilisin-like serine protease. Cleaves prothrombin at 155-Arg-|-Ser-156, 45-Thr-|-Ala-46 and 316-Tyr-|-Ile-317 to produces meizothrombin(desF1)-like molecules. Degrades fibinogen. Inhibits plasma coagulation. Strongly inhibited by antipain and PMSF. Inhibited by benzamidine and aprotinin by 80% and 17% respectively. Little or no inhibition by EDTA, E-64, iodoacetic acid, leupeptin and FUT-175. Optimum pH is 8.0. Retains over 50% of its activity after treatment for 20 min between pH 7.0 and 11.0. Inactivated by treatment at pH 13.0 and at pH values less than 5.0. Optimum temperature is 55 degrees Celsius. Stable from 25 to 40 degrees Celsius. Activity is reduced considerably by incubation above 40 degrees Celsius for 20 min. Homodimer. Belongs to the peptidase S8 family.