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

alpha-1-Antiproteinase E, the fourth isoform of rabbit cr-l antiproteinase (alpha-1-antitrypsin) having a glutamic acid at the reactive center, has be en purified from the plasma by sequential chromatography on hydroxyapatite and anion-exchange columns. The E form of alpha-1-antiproteinase formed a c omplex with trypsin, chymotrypsin, elastase, plasmin and pancreatic kallikr ein as judged by SDS-PAGE. The E form inhibited elastase in a stoichiometri c manner and chymotrypsin moderately, but the inhibition of trypsin was gra dual. The F form inhibited trypsin most effectively followed by chymotrypsi n and elastase. N-chlorosuccinimide reduced the elastase inhibitory activit y of the E form, while the F form was more effectively inactivated by the o xidant.