Activation <i>vs</i>. inhibition of Zn²⁺-TNAP by MgCl₂ and CaCl₂.

<p><b>a</b>. Dose-response of generated AP activity (mean mA405nm/min) in steady-state (i.e. the slope measured between 60–90 min) for increasing [MgCl₂] and [CaCl₂] at identical AbM2-bound [Zn²⁺-TNAP], measured in Chelex-treated pNPP (1 mM) at pH 9.8; <b>b</b>. TNAP inhibition at high [MgCl₂] and [CaCl₂], measured in Chelex-treated pNPP (1 or 10 mM as indicated) at pH 9.8, in the presence of the indicated concentrations of MgCl₂. Results represent mean ± SD for 3 identical experiments or are representative examples of experiments, performed in 3-fold (b, middle and right panel).