Enzymatic characterization of GST-ygiF PPPase activity.
(A) Enzyme activity as a function of PPPi concentration. The curve was obtained by non-linear fitting to the Michaelis-Menten equation. The Mg2+ concentration was 5 mM. (B) PPPase activity as a function of pH at 0.5 mM Mg2+. (C) PPPase activity as a function of Mg2+ concentration. (D) Inhibition of PPPase activity by Ca2+ in the presence of Mg2+ (5 mM). If not otherwise stated, the substrate concentration was 0.5 mM and the incubation was carried out at 50°C and at pH 8.5. (Means ± SD, n = 3).