PathwayStep2766 PathwayStep2767 PathwayStep2768 PathwayStep2769 PathwayStep2765 PathwayStep2770 Uptake of Carbon Dioxide and Release of Oxygen by Erythrocytes Authored: May, B, 2011-03-24 Carbon dioxide (CO2) in plasma is hydrated to yield protons (H+) and bicarbonate (HCO3-) by carbonic anhydrase IV (CA4) located on the apical plasma membranes of endothelial cells. Plasma CO2 is also taken up by erythrocytes via AQP1 and RhAG. Within erythrocytes CA1 and, predominantly, CA2 hydrate CO2 to HCO3- and protons (reviewed in Geers & Gros 2000, Jensen 2004, Boron 2010). The HCO3- is transferred out of the erythrocyte by the band 3 anion exchange protein (AE1, SLC4A1) which cotransports a chloride ion (Cl-) into the erythrocyte.<br>Also within the erythrocyte, CO2 combines with the N-terminal alpha amino groups of HbA to form carbamates while protons bind histidine residues in HbA. The net result is the Bohr effect, a conformational change in HbA that reduces its affinity for O2 and hence assists the delivery of O2 to tissues. Edited: May, B, 2011-03-24 GENE ONTOLOGYGO:0015701 Pubmed10747205 Pubmed15491402 Pubmed19879980 Reactome Database ID Release 431237044 Reactome, http://www.reactome.org ReactomeREACT_121329 Reviewed: Jassal, B, 2012-04-27 H2O + CO2 -> H+ + HCO3- Passive Transport of Carbon Dioxide into the Cell by RhAG Carbonic Anhydrase I/II Hydrates Carbon Dioxide Passive Transport of Carbon Dioxide into the Cell by AQP1 Bohr Effect Exchange of Cytosolic Bicarbonate for Extracellular Chloride by Band 3 Anion Exchanger (AE1, SLC4A1)