Figure 2.

pH profiles of k_cat^ex/K_eff^CO2 (μM⁻¹ s⁻¹) for the hydration of CO₂ catalyzed by variants of HCA II: wild type (black, ●); V143A (blue, △); V143I (red, ■); and V143L (green, ◇). Data were obtained from rates of depletion of ¹⁸O from CO₂ measured by membrane inlet mass spectrometry at 25 °C in solutions containing 25 mM ¹⁸O-enriched CO₂/bicarbonate. No buffers were added.