FIGURE 5.

Inhibition of NeuTTM PPPase by divalent cations. A, inhibition by Ca²⁺ and Mn²⁺ in the presence of Mg²⁺ is shown. The incubation medium contained 0.5 mm PPP_i, 5 mm MgCl₂, 50 mm Na-CHES, pH 9.7, at 37 °C. B, shown is the effect of increasing concentrations of Mg²⁺ (calculated free Mg²⁺) on NeuTTM PPPase activity in the presence or absence of Ca²⁺ ions at 50 °C. The incubation medium contained 0.5 mm PPP_i, 50 mm Na-CHES, pH 9.7. C, shown is the effect of increasing concentrations of ZnSO₄ on the PPPase activity of NeuTTM. The incubation medium contained 0.5 mm PPP_i, 5 mm MgCl₂, 50 mm Na-CHES, pH 9.7, at 37 °C. Results are the mean ± S.D., n = 3.