Glucose-6-phosphatase activity in normal, pre-cancerous, and neoplastic tissues.

Studies on carbohydrate metabolism have re vealed important differences between hepatoma and normal liver. It has been pointed out by Olson (14) that the carbohydrate metabolism of the hepatoma is al tered in such a way that glucose is diverted almost entirely from its storage as glycogen to its degra dation to lactic acid. Olson demonstrated increased phosphohexo-isomerase activity in the hepatoma, which might have an important role in channeling the G-6-P' ester to the glycolytic pathway. On the other hand, Goranson, McBride, and Weber (10) suggested that the diversion of glucose from glyco gen synthesis may be explained in part, at least, by the low activity of the phosphorylase system, which is the rate-limiting step in the G-6-P@±G-1P;:±glycogen reaction. The decreased storage of energy-rich material, such as glycogen, in the hepatoma has also been ex plained by Zamecnik et a!. (18) on the basis that the metabolic activities of the hepatoma cell are adjusted to protein synthesis and growth. The findings of Dickens and Glock (6) that the direct oxidation of G-6-P and 6-phosphogluconate is in creased in liver tumor extract might partially ac count for this latter metabolic change from the normal liver. It seems that the deviation of the carbohydrate metabolism of the hepatoma from that of the nor mal liver starts at the utilization of G-6-P ester. Therefore, the elucidation of the metabolic path ways of G-6-P would bring us nearer to an under standing of this metabolic change in the hepato ma. One of the most important pathways of G-6-P in normal liver is its hydrolysis into glucose and phosphate by the enzyme G-6-Pase.