Figure 3.

Catalytic constants of F226 variants via ¹⁸O exchange. Data for each variant are represented throughout as follows: HCA II, solid black square (■); F226I, open triangle (Δ); F226L, cross (X); F226W, open circle (○). (A) Calculation of k_cat/K_M (M⁻¹ μs⁻1) versus pH from Eq. 3. (B) The pH profile for the rate constant R_H2O/[E] (μs⁻¹) used in calculation of the proton transfer constant, k_B, and pK_a values via Eq. 4.