Isolation and characterization of rabbit plasma alpha-1-antiproteinase E.

Alpha-1-antiproteinase E, the fourth isoform of rabbit alpha-1-antiproteinase (alpha-1-antitrypsin) having a glutamic acid at the reactive center, has been purified from the plasma by sequential chromatography on hydroxyapatite and anion-exchange columns. The E form of alpha-1-antiproteinase formed a complex with trypsin, chymotrypsin, elastase, plasmin and pancreatic kallikrein as judged by SDS-PAGE. The E form inhibited elastase in a stoichiometric manner and chymotrypsin moderately, but the inhibition of trypsin was gradual. The F form inhibited trypsin most effectively followed by chymotrypsin and elastase. N-chlorosuccinimide reduced the elastase inhibitory activity of the E form, while the F form was more effectively inactivated by the oxidant.