Enthalpic partitioning of the reduced temperature sensitivity of O2 binding in bovine hemoglobin

The oxygenation enthalpy of the heme groups of hemoglobin is inherently exothermic, resulting in decreased Hb-O2 affinity with rising temperature

Roy E. Weber

2014

Scholarcy highlights

  • The oxygenation enthalpy of the heme groups of hemoglobin is inherently exothermic, resulting in decreased Hb-O2 affinity with rising temperature
  • Oxygenation is coupled with endothermic dissociation of allosteric effectors from the protein, which reduces the overall oxygenation enthalpy
  • In order to assess the relative contributions from these two effects, we measured the temperature sensitivity of Hb-O2 affinity in bovine and human Hbs in the absence and presence of Cl− ions under strictly controlled pH conditions
  • The data indicate that Cl−-binding accounts for a minority of the total reduction in the oxygenation enthalpy manifested in bovine compared to human Hb, whereas the majority of this reduction is ascribable to structural differences, including increased β-chain hydrophobicity that would increase the heat of oxygenation-linked conformational change in bovine Hb

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