Effect of 2,3-diphosphoglycerate on O2-dissociation kinetics of hemoglobin and glycosylated hemoglobin using the stopped flow technique and an improved in vitro method for hemoglobin glycosylation

: Studies under equilibrium conditions have shown that the oxygen affinity of hemoglobin (Hb) is lowered by 2,3-diphosphoglycerate (2,3-DPG), the physiological allosteric effector in erythrocytes, and enhanced by glycosylation of Hb. The kinetics of oxygen release, as a function of 2,3-DPG and the degree of glycosylation have been determined using the stopped flow method and a new in vitro glycosylation procedure allowing adequate amounts of functionally intact hemoglobin to be obtained. The rate constant k of O2-dissociation in glycosylated Hb (8% HbA1c) was approximately 10% lower than in native Hb (4% HbA1c). The addition of 2,3-DPG in concentrations up to 20 mmol/l resulted in a progressive increase of k from 61.5 +/- 3.3 s-1 to 65.3 ae 4.1 s-1 for native Hb and from 56.8 +/- 5.2 s-1 to 59.4 +/- 4.1 s-1 for glycosylated Hb. We conclude that (a) the degree of glycosylation similar to that found in diabetic patients is responsible for a significant decrease of the oxygen dissociation velocity and (b) 2,3-DPG concentration similar to those occurring in vivo have only a weak effect on the oxygen dissociation velocity.