Chemical Properties
White to off-white powder
Uses
- Glycogen from rabbit liver has been use as a standard for measurement of the hepatic glycogen content.
- In the1,4-α-D gIucan:orthophosphate α-glucosyl transferase assay, it has been used in the assay mixture.
- It has also been used as a standard for myocardial tissue glycogen analysis.
Uses
An inert carrier which significantly increases the efficiency of extracted DNA and RNA by ethanol precipitation.
Uses
glycogen is a skin-conditioning agent. It is a high molecular-weight polymer distributed through the cell protoplasm.
Definition
A glycose polysaccharide, the storage carbohydrate of the animal organism, found especially in the liver and rested muscle.
Definition
A
polysaccharide that is the main carbohydrate
store of animals. It is composed of
many glucose units linked in a similar way
to starch. Glycogen is readily hydrolyzed in
a stepwise manner to glucose itself. It is
stored largely in the liver and in muscle but
is found widely distributed in the body.
General Description
Glycogen is a branched polymer of glucose synthesized by animal cells for energy storage and release. It is constructed of predominantly α1→4 glycosidic bonds with branches created through α1→6 glycosidic bonds.
Biochem/physiol Actions
Glycogen from rabbit liver helps in maintaining blood glucose levels by regulating the release of glucose in between meals. It also provides energy during sudden, strenuous activity. Two important areas of glycogen storage are the liver and skeletal muscle.
Synthesis
Glycogen synthesis occurs in the cytoplasm and can be divided into the following four steps:
(1) Glycogenesis begins with the phosphorylation of glucose by glucokinase in the liver and by hexokinase in muscle and other tissues.
(2) Glucose-6-phosphate is then converted into glucose-1-phosphate by phosphoglucomutase, a reaction similar to that catalysed by phosphoglycerol mutase.
(3) Glucose-1-phosphate is converted into uridine diphosphate (UTP)-glucose, the immediate precursor of glycogen synthesis, by reaction with uridine triphosphate (UTP). This reaction is catalysed by glucose 1-phosphate uridylyltransferase (or UDP-glucose pyrophosphorylase).
(4) Finally, the glucosyl residue at the C-1 position of UDP-glucose is added to the tyrosyl group at position 194 of glycogen protease in an Mg2+-dependent autocatalytic reaction. Glycosidases similarly extend the glucan chain by α(1→4) glycosidic bonds by adding 6 to 7 glucosyl units, using UDP-glucose as the substrate, in an autocatalytic reaction. The glucan primer of glycogen proteins is elongated by glycogen synthase using UDP glucose. Initially, the glycogenin primer and glycogen synthase are strongly bound using a 1:1 complex. As the dextran chain grows, glycogen synthase separates from glycogen.
Purification Methods
A 5% aqueous solution (charcoal) of D(+)-glycogen is filtered, and an equal volume of EtOH is added. After standing overnight at 3o the precipitate is collected by centrifugation, washed with absolute EtOH, then EtOH/diethyl ether (1:1) and diethyl ether, and dried. [Sutherland & Wosilait J Biol Chem 218 459 1956.]
