Reactome: A Curated Pathway Database

Hemoglobin A is protonated and carbamated causing release of oxygen (R-HSA-1237325)

Species Homo sapiens


The Bohr effect refers to the observation that carbon dioxide (CO2) decreases the affinity of hemoglobin (HbA) for oxygen (O2) (Rossi-Bernardi & Roughton 1967, Kwant et al. 1988, Dash & Bassingthwaighte 2010). The Bohr effect has two components: protonation of histidines in HbA (Chatake et al. 2007, Kovalevsky et al. 2010, Fang et al. 1999) and chemical reaction (carbamation) of the N-terminal valines of HbA by CO2 (Ferguson & Roughton 1934, Forster et al. 1968, Bauer & Schroder 1972, Morrow et al. 1973, Morrow et al. 1976, Mathew et al. 1977, Acharya et al. 1994). The protons (H+) for this reaction are produced by carbonic anhydrase acting on water and CO2 to produce bicarbonate (HCO3-) and H+ (Kernohan & Roughton 1968).

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Compartment cytosol
Reverse Reaction Hemoglobin A binds oxygen and releases protons and carbon dioxide
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Literature References
pubMedId Title Journal Year
3136125 Human whole-blood O2 affinity: effect of CO2 J Appl Physiol 1988
16992238 The specific influence of carbon dioxide and carbamate compounds on the buffer power and Bohr effects in human haemoglobin solutions J Physiol 1967
8300612 Electrostatic modification at the amino termini of hemoglobin A J Biol Chem 1994
1395 Carbon 13 resonances of 13CO2 carbamino adducts of alpha and beta chains in human adult hemoglobin J Biol Chem 1976
14958 Quantitative determination of carbamino adducts of alpha and beta chains in human adult hemoglobin in presence and absence of carbon monoxide and 2,3-diphosphoglycerate J Biol Chem 1977
4514311 Interaction of 13 CO 2 and bicarbonate with human hemoglobin preparations Proc Natl Acad Sci U S A 1973
4647257 Carbamino compounds of haemoglobin in human adult and foetal blood J Physiol 1972
17990881 Protonation states of buried histidine residues in human deoxyhemoglobin revealed by neutron crystallography J Am Chem Soc 2007
20230836 Direct determination of protonation states of histidine residues in a 2 A neutron structure of deoxy-human normal adult hemoglobin and implications for the Bohr effect J Mol Biol 2010
21041929 Protonation states of histidine and other key residues in deoxy normal human adult hemoglobin by neutron protein crystallography Acta Crystallogr D Biol Crystallogr 2010
10529219 Assessment of roles of surface histidyl residues in the molecular basis of the Bohr effect and of beta 143 histidine in the binding of 2,3-bisphosphoglycerate in human normal adult hemoglobin Biochemistry 1999
20162361 Erratum to: Blood HbO2 and HbCO2 dissociation curves at varied O2, CO2, pH, 2,3-DPG and temperature levels Ann Biomed Eng 2010
4975618 Thermal studies of the rates of the reactions of carbon dioxide in concentrated haemoglobin solutions and in red blood cells. A. The reactions catalysed by carbonic anhydrase. B. The carbamino reactions of oxygenated and deoxygenated haemoglobin J Physiol 1968
16994616 The chemical relationships and physiological importance of carbamino compounds of CO(2) with haemoglobin J Physiol 1934
5656372 Reaction of CO2 with human hemoglobin solution J Biol Chem 1968