Figure 3
Dependence of ATPase on cations, ATP, Mg2+and pH. In (A), the enzyme activity was measured in the presence of various concentrations of NaCl (closed circle), KCl (open square), LiCl (open rhombus) and CaCl2 (closed triangle). Inset shows a double-reciprocal plot of activity versus NaCl concentration. In (B) and (C), the enzyme activity was measured in the presence of various concentrations of ATP and MgCl2, respectively. Inset in (B) shows a double-reciprocal plot of activity versus ATP concentration. In (D), the enzyme activity was measured at various pH values using 20 mM Mes-KOH for pH 6.0-7.0 (closed rhombus), 20 mM Hepes-KOH for pH 7.0-8.5 (closed triangle), 20 mM Tris-HCl for pH 7.5-9.0 (closed circle) and 20 mM Glycine-KOH for pH 9.0-11.0 (closed square). All data are the average of three independent experiments with vertical bars representing standard errors.