METABOLIC BASIS FOR DISACCHARIDE PREFERENCE IN A CELLVIBRIO

Abstract

The metabolic basis of preferential utilization of cellobiose over glucose has been sought using both intact cells and cell-free preparations of Cellvibrio gilvus. A cellobiose phosphorylase has been demonstrated to initiate metabolism of the disaccharide. Convergence in the metabolism of glucose and cellobiose has been shown to occur at 2 points: by the direct formation of glucose from half of the cellobiose as a result of the phosphorolytic cleavage; and later, by the formation of fructose-6-phosphate from both sugars. The data suggest the hypothesis that the difference between the sugars as energy sources for growth stems from the direct oxidation of glucose to gluconic acid. Cellobiose is cleaved phosphorolytically and further metabolized by reactions leading to more complete oxidation and therefore a greater yield of energy per mole of hexose consumed.