Catalytic Mechanism of α-Class Carbonic Anhydrases: CO2 Hydration and Proton Transfer

The carbonic anhydrases (CAs; EC 4.2.1.1) are a family of metalloenzymes that catalyze the reversible hydration of carbon dioxide (CO2) and dehydration of bicarbonate (HCO3 −) in a two-step ping-pong mechanism: $$ \mathrm{C}{{\mathrm{O}}_2} + {{\mathrm{H}}_2}\mathrm{O}\leftrightarrow \mathrm{HC}{{\mathrm{O}}_3}^{-} + {{\mathrm{H}}^{+}} $$