Irreversible Inhibition of Trypsin by the Disulfide Form of Human Alpha-1 Proteinase Inhibitor

Authors: 0ya 0RTAPAMUK, Nilgün SÜMER, İnci ÖZER

Abstract: The inhibitory properties of the disulfide form of human a-1 proteinase inhibitor (a-1-Pl) were studied, using bovine trypsin as the target protease. Antiprotease activity was found to be kinetically irreversible; treatment of the enzyme-inhibitor complex with a-2 macroglobulin failed to restore the observed esteratic activity of trypsin. a-1-Pl*E was unstable to SDS-PAGE under reducing conditions: A single protein band was observed, with Mr corresponding to 52 000. The results were compared to reports on the reduced (sulfhydryl) form of a-1-Pl, where the enzyme-inhibitor complex is stable both kinetically and electrophoretically. The difference between the two forms of a-1-Pl suggests that the electrophoretic stability of reduced a-1-Pl*E complexes may be due to the presence of an intermolecular disulfide bond between the two proteins.

Keywords: Alpha-1 protienase inhibitor, protease inhibiton.