Fructose, Fructose 1-Phosphate, and Glyceraldehyde Breakdown in Carbohydrate Metabolism

Abstract

Recent investigations showed that all enzymes that are involved in the catabolism of fructose via fructose 1-phosphate (F-1-p) are present in the bovine lens. The present studies were performed to provide information regarding the extent to which fructose, F-1-p and glyceraldehyde (GA) are actually catabolized via this pathway, and how they increase the lactate, α-glycerophosphate and glycerol concentrations. Incubation was performed with a homogenate of bovine lens equator. F-1-p, and particularly fructose + ATP, considerably increased lactate and α-glycerophosphate concentrations, while the glycerol concentration remained unchanged compared to controls. Lactate formation through GA was not observed; while small amounts of glycerol and α- glycerophosphate are formed, it seems that the major part is transformed to glycerate. The results show that the further breakdown of lenticular fructose occurs via F-1-p and that the phosphorylated C3 fragments (dihydroxy-acetone phosphate) are transferred to the energy metabolism, which is not the case with GA.