Figure 3.

Effect of T4MA on the PchP activity measured at low Pcho concentrations. Pcho concentration varied between 0.005 mM and 0.04 mM when the activity was measured in the presence of 3 mM Mg²⁺. With 0.003 mM Zn²⁺ as the activator, the Pcho concentration varied between 0.01 mM and 0.05 mM. As was shown in Figure 1, in these assay conditions there was no enzyme inhibition by high substrate concentrations. 3 mM Mg²⁺ and 0.003 mM Zn²⁺ correspond to three times the K_A values that are shown in Table 1. All determinations were performed in 100 mM sodium acetate buffer, pH 5.0. Because several parts of these experiments were performed with low Pcho concentrations, special care was taken to measure the enzyme activity under strict conditions of initial velocity.