It is a cyclic pentapeptide physiologically active substance produced by fungus F165, and contains four components: A, B, C and D. U937 cells dissolved about 0.8μg fibrin when cultured with fibrin eggs. A, B, C and D all promote the dissolution of fibrinolytic proteins. A 32μmol/L, B 9.8μmol/L, C 24μmol/L, D 7.5μmol/L can enhance the dissolution of cell fibrin by 1.5 times.