Regulation of hexose phosphate metabolism in Acetobacter xylinum

Abstract

The metabolism of glucose and fructose was studied in resting succinate-grown cells of Acetobacter xylinum. From fructose only cellulose and CO2 were formed by the cells, whereas from glucose, gluconate was formed much more rapidly than these two products. The molar ratio of sugar converted into cellulose to sugar converted into CO2 was significantly greater than unity for both hexoses. The pattern of label retention in the cellulose formed by the cells from specifically 14C-labelled glucose, fructose or gluconate corresponded to that of hexose phosphate in a pentose cycle. On the other hand, the isotopic configuration of cellulose arising from variously singly 14C-labelled pyruvate did not agree with the operation of a pentose cycle on gluconeogenic hexose phosphate. Readily oxidizable tricarboxylic acid-cycle intermediates such as acetate, pyruvate or succinate promoted cellulose synthesis from fructose and gluconate although retarding their oxidation to CO2. The incorporation into cellulose of C-1 of fructose was greatly increased in the presence of these non-sugar substrates, although its oxidation to CO2 was greatly diminished. It is suggested that the flow of hexose phosphate carbon towards cellulose or through the pentose cycle in A. xylinum is regulated by an energy-linked control mechanism.