Simultaneous increases of the adenylate energy charge and the rate of glycogen synthesis in nitrogen-starved escherichia coli W4597 (K)

Abstract

When exogenous nitrogen is exhausted in cultures of E. coli W4597 (K) containing excess glucose, the rate of glycogen synthesis increases (3.33-fold), adenylate energy charge increases from 0.74 to 0.87 and FDP decreases (77%). This is the first observation of parallel changes in vivo in the adenylate energy charge and the rate of glycogen synthesis, and of an increase in the adenylate energy charge in vivo with maintenance of the adenine nucleotide pool size and adenylate kinase mass action ratio when growth is limited. This report is also the first direct experimental evidence of the major elements of the Preiss group hypothesis concerning in vivo regulation of bacterial glycogen synthesis by FDP, NADPH, and PLP, the primary activators of ADPG pyrophosphorylase, the rate-limiting enzyme in this synthetic pathway. By taking into account in vitro activities of the enzymes of glycogen metabolism in E. coli W4597(K) and in E. coli B we have concluded that the decrease in FDP is offset by the increase in energy charge and that FDP contributes to the increased rate of glycogen synthesis we observe, while activation by NADPH is improbable. Additional activation by PLP remains a possibility and is discussed.