The Effect of pH and d‐Glycerate 2,3‐Bisphosphate on the O₂ Equilibrium of Norma1 and SH(β93)‐Modified Human Hemoglobin
1982
Antonini, Eraldo | CONDÒ, Saverio G. | GIARDINA, Bruno | IOPPOLO, Carmela | BERTOLLINI, Albcrto
The present paper reports data for the effect of pH and d‐glycerate 2,3‐bisphosphate (d‐glycerate‐2,3‐P₂) on the oxygen equilibrium of norma1 and SH(β93)‐modified human hemoglobin. At sufficiently high d‐glycerate‐2,3‐P₂ concentrations, both oxy and deoxy forms of HbA are saturated with the organic phosphate at a1l pH va1ues between 6 and 9. Furthermore the difference in the affinity for d‐glycerate‐2,3‐P₂ between deoxy and oxy hemoglobin remains constant with pH, implying that the pK va1ues of the Bohr effect groups in deoxy and oxyhemoglobin are not affected by the presence of d‐glycerate‐2,3‐P₂ on the hemoglobin molecule. In the hemoglobins modified in position β93, the difference in affinity between deoxy and oxy hemoglobin for d‐glycerate‐2,3‐P₂ decreases with decrease in pH due mainly to a decrease in the affinity of the deoxy form for d‐glycerate‐2,3‐P₂. The effect of the chemica1 modification appears to be primarily a change in pK of a Bohr group in deoxy hemoglobin which is especia1ly pronounced in the presence of phosphates.
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