PathwayStep2800 PathwayStep2794 PathwayStep2793 PathwayStep2797 PathwayStep2798 PathwayStep2795 PathwayStep2796 PathwayStep2799 Reversible Hydration of Carbon Dioxide Authored: May, B, 2011-08-06 Carbonic anhydrases reversibly catalyze the hydration of carbon dioxide and directly produce bicarbonate and protons, bypassing the formation of carbonic acid (reviewed in Lindskog 1997, Breton 2001, Esbaugh and Tufts 2006, Boron 2010, Gilmour 2010). 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. There are currently 12 known active carbonic anhydrases in humans. Edited: May, B, 2011-08-06 GENE ONTOLOGYGO:0015701 Pubmed11875253 Pubmed16679072 Pubmed19879980 Pubmed20541618 Pubmed9336012 Reactome Database ID Release 431475029 Reactome, http://www.reactome.org ReactomeREACT_121123 Reviewed: Jassal, B, 2012-05-16 Reviewed: Silverman, DN, 2012-05-16 Carbonic Anhydrase Hydrates Carbon Dioxide (plasma membrane) Carbonic Anhydrase Dehydrates Bicarbonate (plasma membrane) Carbonic Anhydrase Hydrates Carbon Dioxide (cytosol) Carbonic Anhydrase Dehydrates Bicarbonate (cytosol) H+ + HCO3- -> H2O + CO2 H2O + CO2 -> H+ + HCO3- Carbonic Anhydrase Dehydrates Bicarbonate (mitochondria) Carbonic Anhydrase Hydrates Carbon Dioxide (mitochondria)