Figure 3. Chemical rescue plots for R301A-PTDH.

(A) Brønsted plot depicting the observed rates of phosphite oxidation by R301A in the presence of various rescue reagents at pH 7.25 as a function of their pK _a. β = 1.03±0.09 (r² = 0.96). (B) Dependence of the rate of chemical rescue on the concentration of aminoguanidine at pH 7.0 (black squares), pH 7.5 (red circles), and pH 8.0 (blue triangles). All data was corrected for the pH-dependence of k _cat,R301A (see Figure S4). Also shown is the expected activity at pH 7.5 (red dashed line) and pH 8.0 (blue dashed line) based on the observed activity at pH 7.0 if the active reagent were the unprotonated aminoguanidine. Experiments were performed in duplicate; when error bars are not visible, the error was smaller than the marker.