FIG. 3.

pH dependence of CsoSCA k_cat for CO₂ hydration. Turnover numbers were calculated by fitting initial rates (8 to 15 independent determinations for each data point) to the Michaelis-Menten equation as described in Materials and Methods and were plotted as log(k_cat) versus pH (○, rCsoSCA; □, broken carboxysomes; ⋄, intact carboxysomes). The buffer/indicator pairs and wavelengths used were MES/chlorophenol red (A₅₇₄) at pH 5.5 to 6.8; MOPS/p-nitrophenol (A₄₀₀) at pH 6.8 to 7.5; HEPES/phenol red (A₅₅₇) at pH 7.5 to 8.0; and TAPS/m-cresol purple (A₅₇₈) at pH 8.0 to 9.0.