Magnesium ions erythrocyte

The free energy of hydrolysis of ATP is also affected by Mg " " and the physiological substrate is Mg " " ATP (or Mg ATP ). The presence of magnesium ions favors ATP hydrolysis because both ADP and Pi have higher affinity (about six times) for Mg + than ATP. In vivo, the AG value for ATP hydrolysis is probably much higher than AG° owing to the prevailing intracellular concentration of the reactants and products (in erythrocytes, —12.4 kcal/mol). 

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