A reassessment of the phosphoglycerate bypass enzymes in human erythrocytes

Dissociation of the human erythrocyte into cytoplasmic and membranous components, shows that all of the cell's intrinsic 2,3-diphosphoglycerate phosphatase activity is associated with the soluble component. Further fractionaction of the cytoplasm on DEAE cellulose illustrates that both 1,3-diphosphoglycerate mutase and 2,3-diphosphoglycerate phosphatase activities occur coincidently within one peak. Thermal denaturation of the peak proteins at 60° results in a parallel loss in phosphatase and mutase activity. The identical phenomenon is observed in the presence of the 2,3-diphosphoglycerate phosphatase activator, 2-phosphoglycolate. Homogeneous 1,3-diphosphoglycerate mutase, which quantitatively accounts for all of the intrinsic 2,3-diphosphoglycerate phosphatase within the red cell, also exhibits thermal instability at 60°. These findings suggest that the phosphoglycerate bypass in erythrocytes is under the control of a single, bifunctional enzyme.