KINETIC STUDIES OF THE REVERSE REACTION CATALYSED BY ADENOSINE TRIPHOSPHATE-CREATINE PHOSPHOTRANSFERASE. THE INHIBITION BY MAGNESIUM IONS AND ADENOSINE DIPHOSPHATE

Publisher Website
Google Scholar
Abstract
Kinetic investigations of the reaction catalyzed by adenosine triphosphate (ATP)-creatine phosphotransferase have been carried out. No firm conclusions could be reached about the reaction of Mg2+ at the nucleotide-binding site of the enzyme. The value of the kinetic constant for this reaction depends on the value used for the apparent stability constant of the metal ion-nucleotide complex and, to a smaller extent, on the method of plotting the results. At higher concentrations Mg2+ is a noncompetitive inhibitor of the enzyme with respect to both magnesium adenosine (MgADP) and phosphocreatine. ADp3- is a competitive inhibitor of the enzyme with respect to MgADP" and a non-competitive inhibitor with respect to phosphocreatine. The concentration of phosphocreatine has little, if any, effect on the kinetic constants for the nucleotide reactants.