A method for specifically removing or isolating plasmin(ogen) or plasmin in presence of fibrinogen from a mixture containing plasmin(ogen) or plasmin by contacting the mixture with a rigid amino acid wherein the amino group of the amino acid and the carboxylic group of the amino acid are about 6-8 Angstroms, preferably about 7 Angstroms apart and the rigid amino acid is covalently bound to the support via the amino group of the amino acid.