Addition of insulin to liver cells from fed rats incubated in the absence of other hormones resulted in a 2-fold increase in glycogen synthase activity. This direct effect of insulin has been characterized and compared with the antagonism by insulin of alpha 1-adrenergic effects on glycogen metabolism. The activation of glycogen synthase by insulin developed slowly (20-25 min) and was most effe...

Here we report the identification of a glycogen phosphorylase (glgP) gene in the plant growth-promoting rhizobacterium Azospirillum brasilense, Sp7, and the characterization of a glgP marker exchange mutant of this strain. The glgP mutant showed a twofold reduction of glycogen phosphorylase activity and an increased glycogen accumulation as compared with wild-type Sp7, indicating that the ident...

It seemed reasonable to suppose that a study of phosphorylase and its activating enzymes in tumor tissues might yield some information bearing upon (a) the characteristically high rate of glucose utilization by tumors (3), and (b) the degree of control eserted by certain hormones over these enzymes in neoplastic cells. In previous studies (4-6) various aspects of carbohydrate metabolism and its...

The concentration of phosphorylase in liver slices changes rapidly in response to certain experimental conditions (14). The concentration of phosphorylase in the cells represents a balance between inactivation of the enzyme and reactivation to the active form. Inactivation of liver phosphorylase is catalyzed by an enzyme formerly designated liver phosphorylase-inactivating enzyme. The synthetic...

Using 13C nuclear magnetic resonance spectroscopic methods we examined in vivo the synthesis of liver glycogen during the infusion of D-[1-13C]glucose and the turnover of labeled glycogen during subsequent infusion of D-[1-13C]glucose. In fasted rats the processes of glycogen synthesis and degradation were observed to occur simultaneously with the rate of synthesis much greater than degradation...

Glycogen disease of the liver (von Gierke's disease) is a rare and incompletely understood disorder of childhood. It is characterized by defective breakdown of liver glycogen to glucose. In most cases, excessive liver glycogen deposition occurs, reaching levels as high as 14 to 17 per cent of the wet liver weight (1, 2). Major clinical manifestations include hepatomegaly; fasting hypoglycemia, ...

Glucose is stored in mammalian tissues in the form of glycogen. Glycogen levels are markedly reduced in liver or muscle cells of patients with insulin-resistant or insulin-deficient forms of diabetes, suggesting that impaired glycogen synthesis may contribute to development of hyperglycemia. Recently, interest in this area has been further stimulated by new insights into the spatial organizatio...

Corynebacterium glutamicum transiently accumulates large amounts of glycogen, when cultivated on glucose and other sugars as a source of carbon and energy. Apart from the debranching enzyme GlgX, which is required for the formation of maltodextrins from glycogen, alpha-glucan phosphorylases were assumed to be involved in glycogen degradation, forming alpha-glucose 1-phosphate from glycogen and ...

Mutant strains of Saccharomyces cerevisiae defective in respiration have been reported to be unable to store glycogen, as revealed by the iodine-staining method. In this report, it is shown that in contrast to this claim, mitochondrial respiratory mutants accumulated even more glycogen than wild-type cells during the fermentative growth on glucose. However, as soon as glucose was exhausted in t...

Ultra-microfluorometric techniques were adapted to follow the time sequence of glycogen degradation during the differentiation of two cell types in Dictyostelium discoideum. Glycogen content, glycogen phosphorylase activity, and inorganic phosphate accumulation were localized in specific cell types during stalk and spore development. Glycogen levels in pre-stalk cells remained constant during t...