Red cell phosphoglycerate mutase and bisphosphoglycerate synthase: Controlled modifications in coulombic properties in vitro

Under controlled conditions, both phosphoglycerate mutase and bisphosphoglycerate synthase from outdated human erythrocytes can be made to manifest changes in coulombic properties as indicated by isoelectric focusing. This finding provides corroborative evidence for the hypothesis that each of the above enzymes arises from its own unique gene locus and is subsequently modified through post-translational events which give rise to other isomeric forms. In the presence of intracellular concentrations of glycerate-2,3-P 2, phosphoglycerate mutase is fully phosphorylated, suggesting a scheme, other than that proposed earlier [Hass, L. F. and Miller, K. B. (1978) J. Biol. Chem. 253 , 3798–3803], to account for all of the mutase isomers found in whole cells. Dephosphorylation of the various mutase species present in circulating cells is accelerated by glycolate-2-P, but not by the normal acceptor, glycerate-3-P, indicating that the enzyme in vivo may be phosphorylated at a site other than the mutase site.