Figure 2

Influence of MgCl ₂ and ATP concentrations on PAPS synthesis. 26 μM Na₂SO₄ (10 μCi of labeled sulfate) was incubated at 37°C in 20 mM Tris-HCl buffer pH 8.5, 5 mM GTP and supplemented with (A): 2 mM ATP, and variable concentrations of MgCl₂: (◆) 1 mM; (■) 2 mM; (▲) 4 mM; (●) 8 mM or (B): 4 mM MgCl₂ and variable concentrations of ATP: (◆) 4 mM; (■) 8 mM; (▲) 16 mM; (●) 32 mM. The reactions were started by addition of 30 μl of yeast extract.