The effect of pH and D-glycerate 2,3-bisphosphate on the O2 equilibrium of normal and SH(beta 93)-modified human hemoglobin.
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 normal and SH(beta 93)-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 all pH values 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 values 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 beta 93, 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 chemical modification appears to be primarily a change in pK of a Bohr group in deoxy hemoglobin which is especially pronounced in the presence of phosphates.
D019794:2,3-Diphosphoglycerate; D055598:Chemical Phenomena; D002621:Chemistry; D004163:Diphosphoglyceric Acids; D006441:Hemoglobin A / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010108:Oxyhemoglobins / Q000378:metabolism*; D013439:Sulfhydryl Reagents
D004163:Diphosphoglyceric Acids; D006454:Hemoglobins; D010108:Oxyhemoglobins; D013439:Sulfhydryl Reagents; D019794:2,3-Diphosphoglycerate; D006441:Hemoglobin A