Metabolism of glycerate-2,3-P2--VI. Lysyl-specific reagents inactivate the phosphoglycerate mutase, glycerate-2,3-P2 synthase and glycerate-2,3-P2 phosphatase activities of rabbit muscle phosphoglycerate mutase.

Treatment of rabbit muscle phosphoglycerate mutase with trinitrobenzenesulfonate and with pyridoxal-5'-phosphate produces the concurrent loss of the three activities of the enzyme: phosphoglycerate mutase, glycerate-2,3-P2 synthase and glycerate-2,3-P2 phosphatase. With both reagents complete inactivation occurs with modification of about 3 moles of lysine per mole of enzyme. Inactivated phosphoglycerate mutase is unable to form the functionally active phosphoenzyme when mixed with glycerate-2,3-P2. Substrate (glycerate-3-P) protects against pyridoxal-5'-phosphate inactivation, and offers some protection against TNBS inactivation. Cofactor (glycerate-2,3-P2) does not prevent inactivation. These results provide additional evidence of the intrinsic character of the three enzymatic activities of phosphoglycerate mutase and favour their location at the same active site. In addition, they suggest that the essential lysyl residues are located at or near the substrate binding site.