title: The effect of alpha 2-macroglobulin on the interaction of alpha 1-proteinase inhibitor with porcine trypsin.
abstract: The rate of dissociation of the alpha 1-proteinase inhibitor:porcine trypsin complex was compared with that in the presence of alpha 2-macroglobulin. In the presence of the latter inhibitor the dissociation was more rapid and active alpha 1-proteinase inhibitor could be recovered in the mixture. However, no active inhibitor could be detected after dissociation in the absence of alpha 2-macroglobulin. This recovery of active alpha 1-proteinase inhibitor from complexes with porcine trypsin is the first demonstration of a thermodynamic equilibrium between this inhibitor and proteinase. Consequently, the transfer of trypsin from complexes with alpha 1-proteinase inhibitor to alpha 2-macroglobulin may be explained as a passive phenomenon which does not require a physical collision between alpha 2-macroglobulin and the alpha 1-proteinase inhibitor:porcine trypsin complex. The dissociation of the complex occurs more rapidly in the presence of alpha 2-macroglobulin because this inhibitor complexes trypsin leaving the alpha 1-proteinase inhibitor:porcine trypsin complex by both the irreversible breakdown step and by reversible dissociation of the complex.
mesh_terms: D000818:Animals; D006801:Humans; D007700:Kinetics; D013552:Swine; D014357:Trypsin / Q000378:metabolism*; D014361:Trypsin Inhibitors; D000515:alpha 1-Antitrypsin / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: D014361:Trypsin Inhibitors; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins; D014357:Trypsin