ABSTRACT
In man and rat fructose is metabolized primarily in the liver, but the intestinal mucosa and kidney also contain enzymes required for the specific metabolism of fructose. Fructose is phosphorylated by fructokinase to fructose-1-phosphate. One of the major consequences of infusions of fructose is the accumulation of high levels of fructose-1-phosphate. Fructose infusions were reported to decrease both ATP and inorganic phosphate levels to about one fourth to one third the normal levels. A recently discovered form of fructose, such as, fructose-2,6-biphosphate may serve as an important regulator of carbohydrate metabolism in the liver. In pancreatic islets, fructose-2,6-biphosphate also acts as an activator of 6-phosphofructo-1-kinase. Fructose-1,6-diphosphatase isolated from various strains of Saccharomyces cerevisiae was incubated with cAMP-dependent protein kinase and fructose-2,6-biphosphate. The bifunctional enzyme which catalyzes the formation and degradation of fructose-2,6-biphosphate was isolated and its properties further characterized by J. Pilkis. Fructose-2,6-biphosphate levels were 10% of normal in livers of both starved and diabetic animals.
