Meta-Biol

• Pathways

Carbonic anhydrase VA (CA5A, Nagao et al. 1993, Franchi et al. 2003, Nishimori et al. 2007) and carbonic anhydrase VB (CA5B, Fujikawa-Adachi et al. 1999, Nishimori et al. 2005, Nishimori et al. 2007) hydrate carbon dioxide in mitochondria to yield bicarbonate and a proton. Carbonic anhydrase deprotonates water to yield a zinc-hydroxyl group and a proton which is transferred to external buffer molecules via histidine or glutamate residues in carbonic anhydrase. The hydroxyl group reacts with carbon dioxide in the active site to yield bicarbonate. A water molecule displaces the bicarbonate and the reaction cycle begins again (reviewed in Lindskog 1997). Depending on the concentrations of reactants the reaction is reversible.