Biosynthesis of bacterial glycogen: characterization of adenosine diphosphate glucose synthetases from Enterobacter hafniae and Aeromonas hydrophila

Enterobacter hafniae and Aeromonas hydrophila ADPglucose synthetases were purified approximately 39-and 61-fold, respectively, over the crude extract. Both enzymes were heat stable at 60°C in the presence of inorganic phosphate. The molecular weights of both enzymes were approximately 200,000 which are similar to other enteric ADPglucose synthetases studied. Based on kinetic results obtained from the partially purified enzymes, the E. hafniae enzyme is activated twofold by phospho-enolpyruvate while the A. hydrophila enzyme is activated twofold by fructose 6-P and 1.5-fold by fructose 1,6 bis-phosphate. The E. hafniae enzyme activity is strongly inhibited by AMP and ADP and the inhibition can be partially reversed by P-enolpyruvate. ADP is the most effective inhibitor of the A. hydrophila enzyme and its inhibiton can be partially overcome by the presence of the activators fructose 6-P and fructose 1,6-P2. These kinetic results show that the allosteric properties of the E. hafniae enzyme are distinctly different from the ADPglucose synthetases of those previously studied from bacteria of the genus Enterobacter. Although the A. hydrophila enzyme is activated by fructose 1,6-P2, its allosteric properties are quite different than those observed for ADPglucose synthetase of the Enterobacteriaceae.