Stabilization of Adenylate Energy Charge by the Adenylate Deaminase Reaction

Abstract

Abstract In the physiological range of the adenylate energy charge in liver (0.7 to 0.9) the rate of deamination of AMP catalyzed by rat liver adenylate deaminase (EC 3.5.4.6) increases sharply with decreasing energy charge. It is suggested that this response serves to protect against sharp transient decreases in energy charge: when the charge decreases the resulting removal of AMP by deamination will oppose the decrease in charge (the mole fraction of ATP plus half the mole fraction of ADP). The activity of the enzyme decreases sharply as the size of the adenine nucleotide pool decreases in and below the physiological range. This effect may be a self-limiting response to prevent excessive depletion of the pool. These suggestions, based on the properties of the enzyme observed in vitro, are consistent with the results of experiments on liver in vivo reported by other workers.