The effects of transgenic overexpression of glycogen synthase in different types of fast-twitch muscle fibers were investigated in individual fibers from the anterior tibialis muscle. Glycogen synthase was severalfold higher in all transgenic fibers, although the extent of overexpression was twofold greater in type IIB fibers. Effects of the transgene on increasing glycogen and phosphorylase an...

It is well known that an alteration in insulin activation of skeletal muscle glycogen synthase is associated with insulin resistance. To determine whether this defect in insulin action is specific to skeletal muscle, or also present in liver, simultaneous biopsies of these tissues were obtained before and during a euglycemic hyperinsulinemic clamp in spontaneously obese insulin-resistant male r...

Native glycogen was isolated from Tetrahymena pyriformis (HSM) by isopycnic centrifugation in cesium chloride density gradients. A density of 1.62 to 1.65 was isopycnic for glycogen. Most of the banded glycogen existed as 35 to 40 mmicro particles which had a sedimentation coefficient of 214. These particles were composed of aggregates of 2 to 3 mmicro spherical particles. Extraction of glycoge...

BACKGROUND Oxygenic photosynthetic microorganisms such as cyanobacteria and microalgae have attracted attention as an alternative carbon source for the next generation of biofuels. Glycogen abundantly accumulated in cyanobacteria is a promising feedstock which can be converted to ethanol through saccharification and fermentation processes. In addition, the utilization of marine cyanobacteria as...

AMP-activated protein kinase (AMPK) is proposed to stimulate fat and carbohydrate catabolism to maintain cellular energy status. Recent studies demonstrate that pharmacologic activation of AMPK and mutations in the enzyme are associated with elevated muscle glycogen content in vivo. Our purpose was to determine the mechanism for increased muscle glycogen associated with AMPK activity in vivo. A...

Glycogen is a branched polymer of glucose that acts as an energy reserve in many cell types. Glycogen contains trace amounts of covalent phosphate, in the range of 1 phosphate per 500-2000 glucose residues depending on the source. The function, if any, is unknown, but in at least one genetic disease, the progressive myoclonic epilepsy Lafora disease, excessive phosphorylation of glycogen has be...

Lafora disease (LD) is an autosomal recessive neurodegenerative disease that results in progressive myoclonus epilepsy and death. LD is caused by mutations in either the E3 ubiquitin ligase malin or the dual specificity phosphatase laforin. A hallmark of LD is the accumulation of insoluble glycogen in the cytoplasm of cells from most tissues. Glycogen metabolism is regulated by phosphorylation ...

Studies by Wagner (1) on the quantitative estimation of glycogen in human blood disclosed the average glycogen content per 100 ml. to be 5.5 mg. In separated leukocytes an average of 2.54 micrograms of glycogen was found per 106 total leukocytes, or 4.23 micrograms per 106 granulocytic leukocytes. No detectable glycogen is present in human plasma or erythrocytes. It has been both denied (2) and...

The major role of liver glycogen is to supply glucose to the circulation in order to maintain normal blood glucose levels. In the muscle and liver, the accumulation and breakdown of glycogen are regulated by the reciprocal activities of glycogen phosphorylase and glycogen synthase. Glycogen phosphorylase catalyses the key step of glycogen degradation and its activity is inhibited by glucose and...