Effects of diet on selected glycolytic enzymes of the rat

Abstract

The activities of selected glycolytic enzymes from the liver and muscle of rats subsisting for 4 and 40 days on carbohydrate-free diets high in fat or protein were compared with enzymes from rats fed high carbohydrate diets. The following changes were noted in liver: high fat—a decrease in phosphorylase, glucokinase, glucose-6-phosphate dehydrogenase and formation of pyruvate from 3-phosphoglycerate with no change in glucose-6-phosphatase; high protein—an increase in phosphorylase and a decrease in glucose-6-phosphatase and glucokinase—the other enzymes were unaffected. These diets had no effect on the activity of the enzymes in muscle, except that the high fat diet depressed muscle glucokinase. Conversely, the activities of muscle phosphorylase and the formation of pyruvate increased with time while the activity of muscle glucose-6-phosphate dehydrogenase decreased. It was concluded that the response of liver glycolytic and oxidative enzymes to carbohydrate removal depended to a large extent upon the nutrient substituted. In muscle, glycolysis was not appreciably affected by dietary manipulations.