Factor IXa enhances reconstitution of factor VIIIa from isolated A2 subunit and A1/A3-C1-C2 dimer.

摘要: Heterotrimeric factor VIIIa was reconstituted from isolated A2 subunit and A1/A3-C1-C2 dimer of thrombin-activated human VIII in a reaction that sensitive to pH. Maximal levels at pH 6.0 were as much 20-fold greater than values observed 7.5. The presence IXa phospholipid resulted marked increase physiologic However, the resultant unstable due slow proteolysis A1 subunit. Factor modified by active site-specific reagent dansyl-glutamyl-glycyl-arginyl-chloromethyl ketone (DEGR-IXa) increased level subunits similar extent for unmodified yielded stable VIIIa. This enhancement saturated above 1:1 molar ratio DEGR-IXa could be blocked an anti-factor IX antibody, suggesting DEGR-IXa-dependent reconstitution correlated with assembly X-ase complex. At saturating amount DEGR-IXa, 7.5 approached obtained 6.0. Fluorescence polarization measurements indicated altered binding phospholipid. neither nor alone produced this effect. result suggested both necessary association cofactor IXa. These results suggest model which intrinsic complex stabilizes through inhibition dissociation.