Regulation of Proteinase Activity by High Molecular Weight Inhibitors: Biosynthesis of Rat α-Macroglobulins

Many proteolytic reactions occur in blood plasma during coagulation, fibrinolysis and complement activation. Particularly during inflammatory processes proteinases such as elastase, collagenase and cathepsin G are released by granulocytes and macrophages1-3. Due to their capability to destroy connective tissues in many organs, these proteinases represent a severe hazard for the organism. It is therefore essential that activated proteinases in plasma are controlled. One way to regulate proteinase activities is by specific inhibitors4-6. Proteinase inhibitors account for about 20% of total proteins in normal rat plasma. Among them there are three proteinase inhibitors of high molecular weight and a wide inhibitory spectrum: α1-macroglobulin, α2-macroglobulin and α1-inhibitor37-13. They belong to the same superfamily and are characterized by their particular mechanism of interaction with proteinases resulting in enzymatically active complexes7,12.