Dietary regulation of 6-phosphogluconate dehydrogenase synthesis.

The relative rates of synthesis and degradation for rat liver 6-phosphogluconate dehydrogenase have been determined in animals maintained at several dietary states. Relative rates of synthesis were determined by pulse-labeling the enzyme either in live rats and determining the radioactivity in the purified enzyme or in whole cell suspensions of hepatocytes followed by precipitation of the enzyme with a specific antiserum. The relative rate of synthesis of the enzyme in rats fed a high carbohydrate fat-free diet was approximately 3.7 to 5.6 times greater than that in animals fed a pellet diet or in fasted rats, respectively. In contrast, a half-life of 13 to 19 hours was determined for the degradation of the enzyme in all three nutritional states. We have concluded that nutritional alterations in the levels of this enzyme in rat liver are caused by alterations in the rate of enzyme synthesis. Glucagon has no effect on the rate of synthesis of this enzyme.