INFLUENCE OF DIET ON THE INVIVO TURNOVER OF GLUCOSE-6-PHOSPHATE-DEHYDROGENASE IN RAT-LIVER

In vivo turnover of rat liver glucose-6-phosphate dehydrogenase was studied. A specific antibody was used in comparing the rates of synthesis and degradation of the enzyme between rats fed a commercial chow diet and those fed a semi-purified high-carbohydrate diet. In livers of rats fed the semi-purified diet, the rate of synthesis of the enzyme was two-fold greater than in livers of rats fed the commercial diet. The rate of degradation of glucose-6-phosphate dehydrogenase was determined by following the loss with time of [guanido-14C]-arginine from previously labelled enzyme. The rate of degradation of the enzyme was decreased in livers of rats fed the semi-purified diet, being 0.044 h-1 (half-life, 16 h) as compared to 0.120 h-1 (half-life, 6 h) in rats fed the chow diet. It was concluded that the increases in enzyme activity observed with this dietary manipulation are solely the result of changes in the rates of synthesis and degradation of enzyme. No evidence was found to support the hypothesis that an activation-inactivation process is involved as a major regulatory mechanism of glucose-6-phosphate dehydrogenase activity in rat liver. © 1979.