Rat liver glucose-6-p dehydrogenase. Dietary regulation of the rate of synthesis.

The rate of synthesis of rat liver glucose-6-P dehydrogenase was determined in hepatocytes isolated from rats in three different nutritional states. In induced rats (fasted 2 days and refed a high carbohydrate diet for 4 days) synthesis of the enzyme represents 0.12% of the total soluble protein synthesized. In rats fed a standard pellet chow diet synthesis of the enzyme is reduced to 0.0067% of the total soluble protein synthesized. In rats fasted for 2 days the rate of glucose-6-P dehydrogenase synthesis is too low to be detected by our methods. In addition, there is a 27-fold difference in the amount 125I-anti-glucose-6-P dehydrogenase serum bound under saturating conditions to polysomes isolated from induced and pellet-fed rats. Both of these methods indicate that there is a large increase in the rate of glucose-6-P dehydrogenase synthesis during the dietary induction of the enzyme. Methods are described for the purification of rat liver glucose-6-P dehydrogenase to homogeneity and the preparation of an antiserum specific for the enzyme. The time course for the increase in the rate of glucose-6-P dehydrogenase and 6-P-gluconate dehydrogenase synthesis in fasted-refed rats suggests that the half-life for the mRNAs coding for the synthesis of both enzymes is 3 to 6 h in the induced rat.