In vitro effect of proteases on human and rat plasma α-macroglobulin activity

Human plasma α₂- macroglobulin activity decreased upon incubation for 12 hours at 37°C in the presence of aminopeptidase (5 μg/0.1 ml), while the immunoreactivity of the inhibitor did not significantly alter under the same conditions. This observation indicates that the inhibitor protein was not extensively degraded on treatment with aminopeptidase. Inactivation of α₂ - macroglobulin by aminopeptidase was found to be a pH and temperature dependent process. While Streptomyces caesiptosus protease (5 μg/0.05 ml) inactivated partially purified human plasma α₂-macroglobulin within fifteen minutes of incubation at 37°C, the action of Streptomyces griseus (15 μg), pronase (15 μg) and aminopeptidase (5μg) appeared to be time dependent. The α-macroglobulin activity in ten fold diluted rat plasma was completely abolished in the presence of Bacillus amyloliquifaciens protease (15μg) whereas, moderate inactivation was observed in the presence of Streptomyces griseus protease (15 μg) and Streptomyces caesiptosus protease (15 μg), upon incubation at 37°C for 12 hours.