Functional assessment of genetic variants of alpha 1-antitrypsin.

The specific activity of thirteen genetic variants of the protease inhibitor alpha 1-antitrypsin (alpha 1AT) has been determined. Elastase inhibitor activity was assayed protein substrates (elastin and gelatin) and the synthetic substrate N-tert-butoxy-carbonyl-L-alanine p-nitrophenyl ester. The synthetic substrate alpha-N-benzoyl-DL-arginine p-nitroanilide HCl was used to assay trypsin inhibitor activity. The specific activity of alpha 1AT was expressed as serum inhibition/immunological concentration of alpha 1AT. Sera of PI type FM had reduced specific activity with elastase, but not with trypsin. With the possible exception of MP, no other variants showed significant differences in specific activity when compared with normal PI type M.