IDENTIFICATION AND PURIFICATION OF A 90-KDA MEMBRANE-BOUND ENDOGENOUSINHIBITOR OF MULTICATALYTIC PROTEINASE FROM HUMAN ERYTHROCYTES

We have identified and purified an endogenous inhibitor of multicataly tic proteinase (MCP) from human erythrocyte membranes. The inhibitor s howed a molecular mass of 90 kDa on sodium dodecyl sulfate-polyacrylam ide gel electrophoresis (SDS-PAGE). The inhibitor protein was purified from the erythrocyte membranes using Heparin-agarose and hydroxylapat ite chromatography and the size exclusion on a Biogel A 1.5 m column i n the presence of high salt. The 90-kDa protein inhibited all three pe ptidase activities of MCP; trypsin-like, chymotrypsin-like and peptidy l glutamyl peptide hydrolyzing (PGPH). However, it failed to cause any significant inhibition of caseinolytic activity of MCP, suggesting th at the regulation of proteinase and peptidase activities is distinct. The inhibition of the chymotrypsin-like activity was noncompetitive. T he results suggest that the 90-kDa inhibitor protein may be an importa nt regulator of membrane-bound MCP. (C) 1995 Academic Press, Inc.