Evidence that cyclic AMP stimulates bacterial glycogen synthesis by relieving AMP inhibition of and by increasing the cellular level of ADP-glucose synthetase.

Using Escherichia coli mutants that possess an ADP-glucose synthetase (EC 2.7.7.27, the rate-limiting enzyme of bacterial glycogen synthesis) that differs in its inhibition by physiological levels of AMP, evidence was obtained that cyclic AMP stimulates cellular glycogen synthesis during nitrogen starvation by relieving AMP inhibition of this enzyme (without altering the cellular AMP level). Deinhibition for AMP of an enzyme controlled by the adenylate energy charge allows selective release from this control despite the maintenance of a constant cellular energy charge value. It was also shown that an additional increase in rate, not accounted for by AMP deinhibition, was due to an increase in the cellular level of ADP-glucose synthetase.