Immunochemical and Enzymatic Properties of Bisphosphoglyceromutase/phosphatase and Phosphoglyceromutase from Human Erythrocytes

We compare human erythrocyte bisphosphoglyceromutase/phosphatase and phosphoglyceromutase in their immunochemical properties and in the functional roles of the amino groups essential for catalytic actions of these enzymes. 1 In Ouchterlony double-immunodiffusion analysis using antisera against bisphosphoglyceromutase/phosphatase obtained from rabbit, bisphosphoglyceromutase/phosphatase gave a single precipitin line, but phosphoglyceromutase did not. The antisera inhibited the three enzyme activities of bisphosphoglyceromutase/phosphatase completely, while phosphoglyceromutase was not inhibited. 2 Initial-velocity studies indicate a sequential mechanism for the phosphoglyceromutase reaction. Phosphoglyceromutase binds 2,3-bisphosphoglycerate 2000 times more tightly than bisphosphoglyceromutase/phosphatase does, whereas 3-phosphoglycerate appears to combine with phosphoglyceromutase much more weakly than it does with bisphosphoglyceromutase/phosphatase. 3 Phosphoglyceromutase was inactivated by trinitrobenzenesulfonate, an amino-group-specific reagent. Monophosphoglycerates afforded strong protective effects, while 2,3-bisphosphoglycerate accelerated the inactivation. Kinetic analyses of the inactivation rate and initial-velocity studies of the enzyme reaction indicate that one amino group per active enzyme unit participates in the binding of 3-phosphoglycerate with the enzyme. The essential amino group of bisphosphoglyceromutase/phosphatase is involved in the 2,3-bisphosphoglycerate binding [cf. Ikura, K. et al. (1976) Eur. J. Biochem. 66, 515–522].