Figure 7. Effect of Ca² on heparin- or sulfated galactan-catalyzed inactivation of GD-factor Xa by antithrombin.

Inactivation of recombinant GD-factor Xa (0.5 nM) by antithrombin (5 nM) was monitored at increasing concentrations of heparin (squares) and sulfated galactan (circles) in TS/PEG buffer, containing either 10 mM CaCl₂ (closed symbols) or 20 mM EDTA (open symbols). The total volume of reaction mixture was 100 μL. After 60 s, the remaining factor Xa activity was determined by the addition of S-2238 or S-2765 susbtrate (25 μL of a 200 μM solution), and substrate hydrolysis was monitored as described in the legend of Fig. 3. *p < 0,05 for ○ vs.●.