Abstract
Plasmin was found to acquire resistance to the inhibition by α2-plasmin inhibitor (α2PI) on incubation at 37°C in 50% glycerin whereas its amidase activity was preserved. This resistance is ascribable to the reduction of the affinity of plasmin to α2PI, since the ability of plasmin to form the complex with α2PI was proved to decrease on incubation. The reduced affinity of pre-incubated plasmin was recovered by incubation with α2PI. The pre-incubation presumably causes a reversible change in the conformation of theα2PI-binding site of plasmin. The use of freshly prepared plasmin solution is recommended for the assay of plasmaα2PI if such an acquired resistance of plasmin is undesirable.
