Figure 5. Time course of LcA reaction using various concentrations of SNAP25 (A), and linear plots of reaction rate (k_obs) calculated at various time points versus SNAP25 concentrations (B).

Each reaction mixture contained 0.2/ml BSA, 5 mM DTT, and 250 µM ZnCl₂, 0.34 nM LcA, and 50 mM Na-HEPES, pH 7.4. The bars inside symbols represent standard deviation of three assays. The lines connecting the data points in B were generated by curve fitting using the Michaelis-Menten equation k_obs = (k_cat×[S])/(K_m+[S]) in a KaleidaGraph software package. K_m and k_cat values derived from these curves are reported in Table 2.