Protease Inhibitors in 3T3 Cells
A 44K anti-thrombin-like protease inhibitor, termed protease-nexin, has recently been discovered in the culture medium of human fibroblasts (Baker et al., 1980). It forms heparin-dependent covalent complexes with the catalytic site of serine proteases. The action of heparin consists in accellerating the formation of the complex by inducing a shape change in the inhibitory site of protease-nexin, which confers to this molecule the affinity for the protease. In the present study we show that 3T3 cells shed into the culture medium at least two inhibitors of exogenous urokinase, which form covalent complexes with the serine-protease. The same study, carried out with 3T3-SV transformed cells, shows a ten fold decrease in the production of both inhibitors.
KeywordsConditioned Medium Fibrinolytic Activity Covalent Complex Inhibitory Site Fibrin Plate
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