pH, Temperature and Lactate Production in Human Red Blood Cells: Implications for Blood Storage and Glycolytic Control

Abstract

The interaction of temperature and pH in biological systems comprises two components. Temperature change may perturb the pH of solutions, and it may change the pKa of some ionizable groups that are involved in enzyme catalysis. The pH optima of single reactions and whole pathways are therefore temperature sensitive. The pH optimum of glycolysis in human red cells has been investigated only at 37 °C. We have measured the effect of temperature on the pH of stored blood suspensions and on the pH optimum of glycolysis in the human red cell. The pH of the cell suspensions in a traditional storage medium was 7.25 ± 0.2 at 4°C. The pH optimum of glycolysis was high (7.8-8.5) between 15 and 35 °C. It can be inferred from our data that human red cells are currently stored at least 0.5 pH units below the pH optimum of glycolysis at 4°C. This suggestion is supported by storage experiments which showed that glycolysis at 4°C was at least 1.5-fold more active at an initial pH of 7.67 versus 7.36. Equations which describe the variation in reaction velocity with pH were fitted to the pH curves for glycolysis in order to identify the ionizable groups that contribute to the effect of pH on glycolysis. It is generally accepted that hexokinase catalyses the rate-limiting step in glycolysis in the human red cell, but none of the ionizable groups implicated correspond to that involved in the hexokinase reaction.

AG-348 enhances pyruvate kinase activity in red blood cells from patients with pyruvate kinase deficiency

“…As RBC metabolite levels can change significantly post-blood draw, 26 we arranged for rapid transport of blood from patient A to our laboratory (within 30 min), along with a time-matched WT control. AG-348 treatment increased PK-R activity and ATP levels to within the range of baseline levels in WT control cells ( Figure 4G), although WT cells had further increased ATP and PK-R activity after AG-348 exposure.…”