Isolation and characterization of rat alpha-1-antitrypsin

From 330 ml of rat serum, 222 mg of alpha-1-antitrypsin have been isolated and purified with an overall yield of approximately 20%. The preparation was homogeneous by the criteria of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, sedimentation equilibrium centrifugation, and immunoelectrophoresis. Rat alpha-1-antitrypsin exhibited Mr = 47,000 +/- 1,500 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 45,000 +/- 1,000 by equilibrium ultracentrifugation; the sedimentation coefficient (s20,w) was 3.29. Rat alpha-1-antitrypsin exhibited a trypsin-combining ratio (moles of trypsin inhibited/mol of alpha-1-antitrypsin) of 0.88. Rat alpha-1-antitrypsin showed significant differences in amino acid composition when compared to human alpha-1-antitrypsin, particularly in lysine, glutamic acid, arginine, methionine, and tyrosine content. Rat alpha-1-antitrypsin contains 14.3 residues/mol of N-acetylglucosamine, 5.0 residues/mol of mannose, 4.2 residues/mol of galactose, and 5.8 residues/mol of sialic acid. Monospecific antibody produced in a rabbit against our purest preparation of rat alpha-1-antitrypsin does not cross-react immunologically against human, calf, fetal calf, mouse, or chicken sera. The availability of a pure preparation of rat alpha-1-antitrypsin as well as the specific alpha-1-antitrypsin antibody will facilitate studies on the biosynthesis and secretion of this important protease inhibitor in an appropriate animal model.