The effect of plasmin on the aPTT coagulant activity of F.IX and F.IXa.

Purified human F.IX or F.IXa (4 μM of each) was incubated either alone (control) or with plasmin (50 nM) in HBS/Ca, pH 7.4 at 37°C. At selected times, 2 aliquots of the same reaction mixtures were removed and assayed for either F.IX aPTT coagulant activity after addition to 2.2 μM of VFK-CMK (A and B) or analyzed by reducing SDS-PAGE (see Figure 2). The relative F.IX and F.IXa aPTT coagulant activity (normalized to the time = 0 sample in each case) versus incubation time with (closed circles) and without (open circles) added plasmin is illustrated in A and B, respectively.