FVa-degrading capacity of recombinant APC variants.

To investigate the efficiency of the various APC variants in an FVa-degradation system, FVa (0.8 nM) from normal (A-B) or FV Leiden (C-D) plasma was incubated at 37°C for 10 minutes with increasing concentrations (A,C) of the various APC variants in the presence of 25 μM phospholipid vesicles (PS/PC, 10:90, wt/wt). The remaining FVa activity was measured with the PTase assay as described in “Materials and methods.” Alternatively, a time course was performed using 0.4 nM APC, and the FVa activity was followed over time using normal FVa (B) or FVa Leiden (D). Concentration courses of FVa inactivation by WT APC and QGNSEDY-APC were measured both in plasma system and plasma-purified FV system. QGNSEDY-APC, (▴); SEDY-APC, (▵); GNED-APC, (▿); QGN-APC, (■); WT APC, (●). Dotted lines with shaded symbols represent the results obtained with plasma-purified FVa. Note the logarithmic y-axes. Each point is the mean of 2 independent experiments performed in duplicate. The error bars were too small to be seen.