BioPAX pathway converted from "Reversible hydration of carbon dioxide" in the Reactome database.

Reversible hydration of carbon dioxide

This event has been computationally inferred from an event that has been demonstrated in another species.

The inference is based on the homology mapping from PANTHER. Briefly, reactions for which all involved PhysicalEntities (in input, output and catalyst) have a mapped orthologue/paralogue (for complexes at least 75% of components must have a mapping) are inferred to the other species. High level events are also inferred for these events to allow for easier navigation.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp 4.2.1.1 Carbonic anhydrase hydrates carbon dioxide (cytosol) Carbonic anhydrase hydrates carbon dioxide (cytosol) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 113528 1 cytosol GO 0005829 carbon dioxide [ChEBI:16526] carbon dioxide Reactome //www.joaskin.com ChEBI 16526 Reactome DB_ID: 29356 1 water [ChEBI:15377] water ChEBI 15377 Reactome DB_ID: 111627 1 hydrogencarbonate [ChEBI:17544] hydrogencarbonate ChEBI 17544 Reactome DB_ID: 70106 1 hydron [ChEBI:15378] hydron ChEBI 15378 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995368 CA1,2,3,7,13:Zinc [cytosol] Converted from EntitySet in Reactome. Each synonym is a name of a PhysicalEntity, and each XREF points to one PhysicalEntity GO 0004089 GO molecular function Reactome Database ID Release 77 9995369 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995369 Reactome Database ID Release 77 9995375 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995375 Reactome R-CFA-1475026 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475026.1 Carbonic anhydrase I (CA1, Khalifah 1971, Simonsson et al. 1982, Ren and Lindskog 1992), carbonic anyhydrase II (CA2, Tibell et al. 1984, Jones and Shaw 1983, Pesando 1975, Ghannam et al. 1986), carbonic anhydrase III (CA3, Carter et al. 1979, Tu et al. 1990, Tu et al. 1994, Tu et al. 1998, Silverman et al. 1993), carbonic anhydrase VII (CA7, Bootorabi et al. 2010, Gitto et al. 2010) hydrate carbon dioxide 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.
CA2 and CA7 have high catalytic activity, CA1 has low activity (10% of the activity of CA2), and CA3 has very low activity (1% of the activity of CA2). CA1 and CA2 are found in erythrocytes. CA2 is also found in kidney, lung, and white muscle where it facilitates diffusion of carbon dioxide. CA3 is found in red muscle where it participates in resistance against oxidative stress. 20578724 Pubmed 2010 Structural and kinetic study of the extended active site for proton transfer in human carbonic anhydrase II Domsic, JF Williams, W Fisher, SZ Tu, C Agbandje-McKenna, M Silverman, DN McKenna, R Biochemistry 49:6394-9 6407977 Pubmed 1983 A chemical and enzymological comparison of the common major human erythrocyte carbonic anhydrase II, its minor component, and a new genetic variant, CA II Melbourne (237 Pro leads to His) Jones, GL Shaw, DC Hum Genet 63:392-9 120192 Pubmed 1979 Characterization of human carbonic anhydrase III from skeletal muscle Carter, N Jeffery, S Shiels, A Edwards, Y Tipler, T Hopkinson, DA Biochem Genet 17:837-54 1554744 Pubmed 1992 Buffer dependence of CO2 hydration catalyzed by human carbonic anhydrase I Ren, X Lindskog, S Biochim Biophys Acta 1120:81-6 8399223 Pubmed 1993 Rate-equilibria relationships in intramolecular proton transfer in human carbonic anhydrase III Silverman, DN Tu, C Chen, X Tanhauser, SM Kresge, AJ Laipis, PJ Biochemistry 32:10757-62 8083199 Pubmed 1994 Interactions of active-site residues and catalytic activity of human carbonic anhydrase III Tu, C Chen, X Ren, X LoGrasso, PV Jewell, DA Laipis, PJ Silverman, DN J Biol Chem 269:23002-6 20493921 Pubmed 2010 Analysis of a shortened form of human carbonic anhydrase VII expressed in vitro compared to the full-length enzyme Bootorabi, F Jänis, J Smith, E Waheed, A Kukkurainen, S Hytönen, V Valjakka, J Supuran, CT Vullo, D Sly, William S Parkkila, S Biochimie 92:1072-80 3080418 Pubmed 1986 Activation parameters for the carbonic anhydrase II-catalyzed hydration of CO2 Ghannam, AF Tsen, W Rowlett, RS J Biol Chem 261:1164-9 9635771 Pubmed 1998 Properties of intramolecular proton transfer in carbonic anhydrase III Tu, C Qian, M Earnhardt, JN Laipis, PJ Silverman, DN Biophys J 74:3182-9 9336012 Pubmed 1997 Structure and mechanism of carbonic anhydrase Lindskog, S Pharmacol Ther 74:1-20 4994926 Pubmed 1971 The carbon dioxide hydration activity of carbonic anhydrase. I. Stop-flow kinetic studies on the native human isoenzymes B and C Khalifah, RG J Biol Chem 246:2561-73 2169869 Pubmed 1990 Buffer enhancement of proton transfer in catalysis by human carbonic anhydrase III Tu, CK Paranawithana, SR Jewell, DA Tanhauser, SM LoGrasso, PV Wynns, GC Laipis, PJ Silverman, DN Biochemistry 29:6400-5 6433979 Pubmed 1984 Anion inhibition of CO2 hydration catalyzed by human carbonic anhydrase II. Mechanistic implications Tibell, L Forsman, C Simonsson, I Lindskog, S Biochim Biophys Acta 789:302-10 234739 Pubmed 1975 Proton magnetic resonance studies of carbonic anhydrase. II. Group controlling catalytic activity Pesando, JM Biochemistry 14:681-8 17427958 Pubmed 2007 Structural and kinetic analysis of proton shuttle residues in the active site of human carbonic anhydrase III Elder, I Fisher, Z Laipis, PJ Tu, C McKenna, R Silverman, DN Proteins 68:337-43 21282642 Pubmed 2011 Intramolecular proton shuttle supports not only catalytic but also noncatalytic function of carbonic anhydrase II Becker, HM Klier, M Schüler, C McKenna, R Deitmer, JW Proc Natl Acad Sci U S A 108:3071-6 6819139 Pubmed 1982 A 13C nuclear magnetic resonance study of CO2/HCO-3 exchange catalyzed by human carbonic anhydrase I Simonsson, I Jonsson, BH Lindskog, S Eur J Biochem 129:165-9 20349499 Pubmed 2010 Identification of potent and selective human carbonic anhydrase VII (hCA VII) inhibitors Gitto, R Agnello, S Ferro, S Vullo, D Supuran, CT Chimirri, A ChemMedChem 5:823-6 22001224 Pubmed 2011 Structure and catalysis by carbonic anhydrase II: role of active-site tryptophan 5 Mikulski, R Domsic, JF Ling, G Tu, C Robbins, AH Silverman, DN McKenna, R Arch Biochem Biophys 516:97-102 inferred by electronic annotation IEA GO IEA 4.2.1.1 Carbonic anhydrase dehydrates bicarbonate (cytosol) Carbonic anhydrase dehydrates bicarbonate (cytosol) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 111627 1 Reactome DB_ID: 70106 1 Reactome DB_ID: 113528 1 Reactome DB_ID: 29356 1 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995368 Reactome Database ID Release 77 9995371 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995371 Reactome R-CFA-1475022 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475022.1 Carbonic anhydrase I (CA1, Khalifah 1971, Simonsson et al. 1982, Ren and Lindskog 1992), carbonic anyhydrase II (CA2, Tibell et al. 1984, Jones and Shaw 1983, Pesando 1975, Ghannam et al. 1986), carbonic anhydrase III (CA3, Carter et al. 1979, Tu et al. 1990, Tu et al. 1994, Tu et al. 1998, Silverman et al. 1993), carbonic anhydrase VII (CA7, Bootorabi et al. 2010, Gitto et al. 2010) dehydrate cytosolic bicarbonate to yield water and carbon dioxide (reviewed in Lindskog 1997). Depending on the concentrations of reactants the reaction is reversible.
CA2 and CA7 have high catalytic activity, CA1 has low activity (10% of the activity of CA2), and CA3 has very low activity (1% of the activity of CA2). CA1 and CA2 are found in erythrocytes. CA2 is also found in kidney, lung, and white muscle where it facilitates diffusion of carbon dioxide. CA3 is found in red muscle where it participates in resistance against oxidative stress. inferred by electronic annotation IEA GO IEA 4.2.1.1 碳酸酐酶水合物二氧化碳(等离子体membrane) 碳酸酐酶水合物二氧化碳(等离子体membrane) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 1237009 1 extracellular region GO 0005576 Reactome DB_ID: 109276 1 Reactome DB_ID: 351626 1 Reactome DB_ID: 425425 1 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995339 plasma membrane GO 0005886 CA4,9,14,12:Zn2+ [plasma membrane] Converted from EntitySet in Reactome. Each synonym is a name of a PhysicalEntity, and each XREF points to one PhysicalEntity Reactome Database ID Release 77 9995340 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995340 Reactome Database ID Release 77 9995373 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995373 Reactome R-CFA-1475025 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475025.1 碳酸酐酶IV (Okuy CA4,朱镕基和狡猾的1990年ama et al. 1992, Baird et al. 1997, Innocenti et al. 2004), carbonic anhydrase IX (CA9, Wingo et al. 2001, Hilvo et al. 2008), carbonic anhydrase XII (CA12, Ulmasov et al. 2000, Pastorekova et al. 2008), and carbonic anhydrase XIV (CA14Ozensoy et al. 2005, Temperini et al. 2008) are membrane-bound enzymes that hydrate extracellular carbon dioxide 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.
CA4 has high catalytic activity. CA9, CA12, and CA14 have moderate activity. CA4 is anchored to the extracellular face of the plasma membrane by glycosylphosphatidylinositol. CA9, CA12, and CA14 are single-pass transmembrane proteins. CA4 is found on the extracellular face of capillaries in kidney, lung, and muscle where it maintains the gradient of carbon dioxide between tissue and blood. CA9 and CA12 are found on basolateral membranes of epithelia. CA9 is inducible by Hypoxia-inducible factor 1 alpha (HIF1alpha) and acidifies the extracellular environment of tumors. In rodents CA15 is membrane anchored and has low activity; in primates CA15 is a pseudogene. 18703501 Pubmed 2008 Biochemical characterization of CA IX, one of the most active carbonic anhydrase isozymes Hilvo, M Baranauskiene, L Salzano, AM Scaloni, A Matulis, D Innocenti, A Scozzafava, A Monti, SM Di Fiore, A De Simone, G Lindfors, M Jänis, J Valjakka, J Pastoreková, S Pastorek, J Kulomaa, MS Nordlund, HR Supuran, CT Parkkila, S J Biol Chem 283:27799-809 18294854 Pubmed 2008 Carbonic anhydrase activators: activation of the human tumor-associated isozymes IX and XII with amino acids and amines Pastorekova, S Vullo, D Nishimori, I Scozzafava, A Pastorek, J Supuran, CT Bioorg Med Chem 16:3530-6 7625839 Pubmed 1995 Carbonic anhydrase IV: role of removal of C-terminal domain in glycosylphosphatidylinositol anchoring and realization of enzyme activity Okuyama, T Waheed, A Kusumoto, W Zhu, XL Sly, William S Arch Biochem Biophys 320:315-22 18162396 Pubmed 2008 Carbonic anhydrase inhibitors. Interaction of 2-N,N-dimethylamino-1,3,4-thiadiazole-5-methanesulfonamide with 12 mammalian isoforms: kinetic and X-ray crystallographic studies Temperini, C Cecchi, A Boyle, NA Scozzafava, A Cabeza, JE Wentworth P, Jr Blackburn, GM Supuran, CT Bioorg Med Chem Lett 18:999-1005 11676494 Pubmed 2001 The catalytic properties of human carbonic anhydrase IX Wingo, T Tu, C Laipis, PJ Silverman, DN Biochem Biophys Res Commun 288:666-9 9054574 Pubmed 1997 Catalysis and inhibition of human carbonic anhydrase IV Baird TT, Jr Waheed, A Okuyama, T Sly, William S Fierke, CA Biochemistry 36:2669-78 11121027 Pubmed 2000 Purification and kinetic analysis of recombinant CA XII, a membrane carbonic anhydrase overexpressed in certain cancers Ulmasov, B Waheed, A Shah, GN Grubb, JH Sly, William S Tu, C Silverman, DN Proc Natl Acad Sci U S A 97:14212-7 15501038 Pubmed 2004 Carbonic anhydrase inhibitors: inhibition of the membrane-bound human isozyme IV with anions Innocenti, A Firnges, MA Antel, J Wurl, M Scozzafava, A Supuran, CT Bioorg Med Chem Lett 14:5769-73 2111324 Pubmed 1990 Carbonic anhydrase IV from human lung. Purification, characterization, and comparison with membrane carbonic anhydrase from human kidney Zhu, XL Sly, William S J Biol Chem 265:8795-801 16006130 Pubmed 2005 Carbonic anhydrase inhibitors: inhibition of the human transmembrane isozyme XIV with a library of aromatic/heterocyclic sulfonamides Ozensoy, O Nishimori, I Vullo, D Puccetti, L Scozzafava, A Supuran, CT Bioorg Med Chem 13:6089-93 inferred by electronic annotation IEA GO IEA 4.2.1.1 Carbonic anhydrase dehydrates bicarbonate (plasma membrane) Carbonic anhydrase dehydrates bicarbonate (plasma membrane) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 351626 1 Reactome DB_ID: 425425 1 Reactome DB_ID: 1237009 1 Reactome DB_ID: 109276 1 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995339 Reactome Database ID Release 77 9995342 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995342 Reactome R-CFA-1475017 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475017.1 碳酸酐酶IV (Okuy CA4,朱镕基和狡猾的1990年ama et al. 1992, Baird et al. 1997, Innocenti et al. 2004), carbonic anhydrase IX (CA9, Wingo et al. 2001, Hilvo et al. 2008), carbonic anhydrase XII (CA12, Ulmasov et al. 2000, Pastorekova et al. 2008), and carbonic anhydrase XIV (CA14, Ozensoy et al. 2005, Temperini et al. 2008) are membrane-bound enzymes that dehydrate bicarbonate to yield water and carbon dioxide. Depending on the concentrations of reactants the reaction is reversible.
CA4 has high catalytic activity. CA9, CA12, and CA14 have moderate activity. CA4 is anchored to the extracellular face of the plasma membrane by glycosylphosphatidylinositol. CA9, CA12, and CA14 are single-pass transmembrane proteins. CA4 is found on the extracellular face of capillaries in kidney, lung, and muscle where it maintains the gradient of carbon dioxide between tissue and blood. CA9 and CA12 are found on basolateral membranes of epithelia. CA9 is inducible by Hypoxia-inducible factor 1 alpha (HIF1alpha) and acidifies the extracellular environment of tumors. In rodents CA15 is membrane anchored and has low activity; in primates CA15 is a pseudogene. inferred by electronic annotation IEA GO IEA 4.2.1.1 Carbonic anhydrase hydrates carbon dioxide (mitochondria) Carbonic anhydrase hydrates carbon dioxide (mitochondria) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 113521 1 mitochondrial matrix GO 0005759 Reactome DB_ID: 29376 1 Reactome DB_ID: 113529 1 Reactome DB_ID: 29896 1 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995389 CA5A,B:Zinc [mitochondrial matrix] Converted from EntitySet in Reactome. Each synonym is a name of a PhysicalEntity, and each XREF points to one PhysicalEntity Reactome Database ID Release 77 9995390 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995390 Reactome Database ID Release 77 9995394 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995394 Reactome R-CFA-1475032 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475032.1 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. 10409679 Pubmed 1999 Human mitochondrial carbonic anhydrase VB. cDNA cloning, mRNA expression, subcellular localization, and mapping to chromosome x Fujikawa-Adachi, K Nishimori, I Taguchi, T Onishi, S J Biol Chem 274:21228-33 14611844 Pubmed 2003 Carbonic anhydrase inhibitors: inhibition of human and murine mitochondrial isozymes V with anions Franchi, M Vullo, D Gallori, E Antel, J Wurl, M Scozzafava, A Supuran, CT Bioorg Med Chem Lett 13:2857-61 16302824 Pubmed 2005 Carbonic anhydrase inhibitors. The mitochondrial isozyme VB as a new target for sulfonamide and sulfamate inhibitors Nishimori, I Vullo, D Innocenti, A Scozzafava, A Mastrolorenzo, A Supuran, CT J Med Chem 48:7860-6 8356065 Pubmed 1993 人类线粒体碳酸酐酶:cDNA cloning, expression, subcellular localization, and mapping to chromosome 16 Nagao, Y Platero, JS Waheed, A Sly, William S Proc Natl Acad Sci U S A 90:7623-7 17761422 Pubmed 2007 Carbonic anhydrase inhibitors: the inhibition profiles of the human mitochondrial isoforms VA and VB with anions are very different Nishimori, I Innocenti, A Vullo, D Scozzafava, A Supuran, CT Bioorg Med Chem 15:6742-7 inferred by electronic annotation IEA GO IEA 4.2.1.1 Carbonic anhydrase dehydrates bicarbonate (mitochondria) Carbonic anhydrase dehydrates bicarbonate (mitochondria) This event has been computationally inferred from an event that has been demonstrated in another species.

More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp Reactome DB_ID: 113529 1 Reactome DB_ID: 29896 1 Reactome DB_ID: 113521 1 Reactome DB_ID: 29376 1 PHYSIOL-LEFT-TO-RIGHT ACTIVATION Converted from EntitySet in Reactome Reactome DB_ID: 9995389 Reactome Database ID Release 77 9995392 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=9995392 Reactome R-CFA-1475028 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475028.1 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) dehydrate bicarbonate in mitochondria to yield water and carbon dioxide (reviewed in Lindskog 1997). Depending on the concentrations of reactants the reaction is reversible. inferred by electronic annotation IEA GO IEA Canis familiaris NCBI Taxonomy 9615 Reactome Database ID Release 77 10046021 Database identifier. Use this URL to connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser?DB=gk_current&ID=10046021 Reactome R-CFA-1475029 1 Reactome稳定的标识符。使用这个URL connect to the web page of this instance in Reactome: //www.joaskin.com/cgi-bin/eventbrowser_st_id?ST_ID=R-CFA-1475029.1 GO 0015701 GO biological process 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. 16679072 Pubmed 2006 The structure and function of carbonic anhydrase isozymes in the respiratory system of vertebrates Esbaugh, AJ Tufts, BL Respir Physiol Neurobiol 154:185-98 11875253 Pubmed 2001 The cellular physiology of carbonic anhydrases Breton, S JOP 2:159-64 20541618 Pubmed 2010 Perspectives on carbonic anhydrase Gilmour, KM Comp Biochem Physiol A Mol Integr Physiol 157:193-7 19879980 Pubmed 2010 Evaluating the role of carbonic anhydrases in the transport of HCO3--related species Boron, WF Biochim Biophys Acta 1804:410-21 inferred by electronic annotation IEA GO IEA