Utilization of Fructose-1,6-Diphosphate as Glycolytic Substrate in Bovine Lens Homogenates

Cortex and nucleus of bovine lenses of different ages were homogenized and incubated in the presence of glucose at 37°C for different periods. A balance of the free adenine nucleotides is produced, which is nearly independent of the amount of glucose added (12.5; 25; 37 mM) and shows certain deviations from the physiologic values. These might be interpreted as due to a decreased rate of glycolytic catabolization. Possibly the phosphorylation of the glucose, which is present in sufficient amounts, is inhibited. If, for instance, fruetose-l,6-diphosphate in a concentration of 10−4 M is added to homogenates with such a disturbed nucleotide balance, a normalization takes place within 30 min, and the values of the initial physiologic equilibrium are restored. Due to the difference in the metabolic condition, there are differences between the behaviour of the cortex homogenate and that of the nucleus. The original equilibrium of the free nucleotides present in homogenates of lens nuclei is more stable during incubation in the presence of glucose. Most obvious is the improvement of the equilibrium in the presence of fructose-1,6-diphosphate. Besides the analytical evaluation of the free nucleotides the values of the concentrations of di-hydroxyacetone-phosphate, pyruvic acid and lactate clearly show that fructose-1,6-diphosphate may be utilized as a substrate for the glycolysis of lens homogenates.