Functional Properties of Two Different Molecular Forms of α2-Plasmin Inhibitor release_5p7z5saberh7tly6fp6ymcus7q

Abstract

The α2-plasmin inhibitor in plasma exists in at least two molecular forms (1). One form (PB) binds to plasminogen-Sepharose. The other form (NPB) comprising around 0.4 of the total amount of the inhibitor in plasma does not bind to plasminogen-Sepharose. PB was purified by affinity chromato-graphy (1) while NPB was partially purified by conventional methods (2). Both inhibitor forms inhibited plasmin in a fast reaction and the change in catalytic concentration of plasmin with increasing concentrations of both forms was a linear function. At identical active site concentrations of the two forms (titrated with pNPGB-titrated plasmin) PB produced a more marked inhibition of urokinase-induced fibrinolysis. Similanly PB produced a more marked decrease of the binding af Lys-plasminogen to fibrin than NPB. The results indicate that an equilibrium between the 2 forms may be important for the biological regulation of the inhibition of plasmin.
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