Partial primary structure of human alpha 2-antiplasmin-homology with other plasma protease inhibitors.

Human alpha 2-antiplasmin was digested with trypsin and with chymotrypsin and about 70 percent of the amino acids were sequenced and aligned in peptides ranging from 2 to 33 residues. Here we report five sequences of 21 to 33 residues. When these were compared with the primary structures of antithrombin III, alpha 1-antitrypsin and ovalbumin, which belong to the same protein superfamily (Hunt and Dayhoff [1980] Biochem Biophys Res Commun 95: 864-871), three peptides showed clear homologies with these proteins, indicating that alpha 2-antiplasmin also belongs to that superfamily. In addition, alpha 2-antiplasmin appeared to contain at least one internal homology.