Effect of EGR-factor IXa and factor X on the inactivation of factor VIIIa by human APC and protein S.

(A) Factor VIIIa activity was determined for reactions containing 200 nmol/L factor VIIIa alone (open diamonds), factor VIIIa plus 40 nmol/L APC, and 400 nmol/L each EGR-factor IXa and factor X in the absence (open circles) and presence (closed circles) of 250 nmol/L protein S. (B) Residual A1 (circles) and A2 (squares) subunits were determined for the above reactions. Open and closed symbols represent the absence and presence of protein S, respectively.