2,3-Bisphosphoglycerate in developing rabbit erythroid cells.

Rabbits were made anemic to different extents by phenylhydrazine injections so as to vary the developmental stages of the erythroid cells in their peripheral blood and bone marrow. It was found that the more severe the anemia, the lower the concentration of glycerate-2,3-P2 in the bone marrow cells and in the circulating erythroid cells. The glycerate-2,3-P2 level was shown to rise during erythroid differentiation in a linear relationship to the hemoglobin level, corresponding to the equation Y = 0.03x + 0.29, where y is the concentration of glycerate-2,3-P2 (micromoles per ml packed cells) and x is the concentration of hemoglobin (milligrams per packed cells). The bone marrow cells were fractionated on a size (i.e. maturity) basis and enzyme activities in the fractionated cells were measured. The accumulation of glycerate-2,3-P2 was found to be primarily attributable to the increase in glycerate-2,3-P2 synthase activity. Glycerate-2,3-P2 phosphatase and phosphofructokinase increased as the cells matured from the polychromatic stages to become reticulocytes while pyruvate kinase and phosphoglyceromutase decreased. The changes in phosphofructokinase and pyruvate kinase appear to be advantageous for glycerate-2,3-P2 accumulation. The two enzyme activities directly responsible for the synthesis and the breakdown of glycerate-2,3-P2 are probably manifested by a single protein, glycerate-2,3-P2 synthase-phosphatase.