A protein chosen from the group consisting of: i) proteins comprising the sequence SEQ ID NO: 2 or SEQ ID NO: 25, preferably consisting of SEQ ID NO: 2 or of the association of SEQ ID NO: 25 and SEQ ID NO: 26, wherein said sequence comprises: a mutation A consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, or a double mutation A and B consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, and the replacement of arginine in position 275 of SEQ ID NO: 2 or SEQ ID NO: 25 by serine, ii) proteins comprising a sequence having at least 90% homology with SEQ ID NO: 2, said proteins comprising mutation A or double mutation A and B, or proteins comprising a sequence having at least 90% homology with SEQ ID NO: 25, said proteins comprising mutation A or double mutation A and B; wherein said proteins have fibrinolytic activity, and iii) proteins consisting of a fragment of SEQ ID NO:2, said fragment consisting of the Kringle 2 domain and the catalytic domain, said proteins comprising mutation A or double mutation A and B. i) proteins comprising the sequence SEQ ID NO: 2 or SEQ ID NO: 25, preferably consisting of SEQ ID NO: 2 or of the association of SEQ ID NO: 25 and SEQ ID NO: 26, wherein said sequence comprises: a mutation A consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, or a double mutation A and B consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, and the replacement of arginine in position 275 of SEQ ID NO: 2 or SEQ ID NO: 25 by serine, a mutation A consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, or a double mutation A and B consisting of the replacement of tryptophan in position 253 of SEQ ID NO: 2 or SEQ ID NO: 25 by a hydrophilic amino acid chosen from arginine, aspartic acid, glutamic acid, lysine, asparagine, glutamine, serine, threonine, tyrosine and histidine, and the replacement of arginine in position 275 of SEQ ID NO: 2 or SEQ ID NO: 25 by serine, ii) proteins comprising a sequence having at least 90% homology with SEQ ID NO: 2, said proteins comprising mutation A or double mutation A and B, or proteins comprising a sequence having at least 90% homology with SEQ ID NO: 25, said proteins comprising mutation A or double mutation A and B; wherein said proteins have fibrinolytic activity, and iii) proteins consisting of a fragment of SEQ ID NO:2, said fragment consisting of the Kringle 2 domain and the catalytic domain, said proteins comprising mutation A or double mutation A and B.