Proteolytic Activation of Glucose-6-phosphatase in Normal, Diabetic and Hepatomic Rat Livers

Abstract

PHOSPHORYLATION of glucose, the hexokinase reaction, is an irreversible one which, however, is reversible by a specific phosphatase, the glucose-6-phosphatase (G-6-pase). Therefore the velocity of the phosphorylation of glucose is not only dependent on the activity of the hexokinase, but is also a result of the contrary action of both the enzymes. It was shown by some authors^1,2 that the activity of G-6-pase is different in varying conditions of metabolism. Tissues or cells with a high catabolism of carbohydrates show a significantly decreased activity of G-6-pase, besides an increased activity of hexokinase². Highly glycolysing tumours represent tissues with a remarkable catabolism of carbohydrates and also show a decreased activity of G-6-pase^3,4. Hitherto no tumour has been found with a noticeable activity of this enzyme. On the other hand, it will be expected that tissues with a diminished consumption of glucose or increased synthesis of glucose from non-carbohydrate sources via the Embden–Meyerhof pathway exhibit an enhanced activity of G-6-pase. Accordingly Mokrasch¹ found increased activity of phosphatase in diabetic liver.