[Rat liver phosphoglycerate kinase. I. Purification and kinetic properties in the biosynthesis of 1-3...

Phosphoglycerate kinase (MgATP 3-phospho-D-glycerate 1-phosphotransferase, EC 2.7.2.3) has been isolated from rat liver with a purification ratio of 960 and a specific activity of 300 IU/mg of protein. The purity of the enzyme preparations was estimated by polyacrylamide gel electrophoresis. The molecular weight, determined by gel filtration is 42 000. The "subunit" size of phosphoglycerate kinase as determined by sodium dodecyl sulfate gel electrophoresis is 46 000, indicating that the enzyme is monomeric. The rate of the enzyme reaction as a function of the concentration of D-3-phosphoglycerate indicated the usual Michaelis Menten relationship. The rate of the enzyme reaction as a function of the concentration of MgATP2- did not fit the usual Michaelis Menten relationship: two distinct regions can be fitted with different straight lines and suggest the presence of two sites for the Mg ATP2-. This hypothesis seems to be confirmed by the study of the action of the free and complexed nucleotides.