Phosphorylation as a method of regulating the activity of inorganic pyrophosphatase. II. Characteristics of the regulatory site

Monosubstituted derivatives of pyrophosphoric acid activate the hydrolysis of magnesium pyrophosphate catalyzed by yeast inorganic pyrophosphatase by phosphorylating the carboxy group of the regulatory site of the enzyme. An activating action is exhibited by compounds present in the free form and not in the form of complexes with magnesium ions, but the latter are necessary for creating the reactive conformation of the protein. ATP and inorganic phosphate compete in the phosphorylation of inorganic pyrophosphatase, bu the phosphate acceptors in these cases are different amino acid residues of the enzyme. The mechanism of the regulation of the activity of pyrophosphatase under the action of monosubstituted derivatives of pyrophosphoric acid and phosphate is discussed