Glycogen phosphorylase

Liver glycogen phosphorylaseliver glycogenliver phosphorylaseMuscle glycogen phosphorylasePhosphorylase ''a
Glycogen phosphorylase is one of the phosphorylase enzymes.wikipedia
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Glycogenolysis

breakdown of glycogenbreakdownglycogen degradation
Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond.
Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase.

Glucose 1-phosphate

glucose-1-phosphatebeta-D-glucose 1-phosphateCori ester
Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. Glycogen is left with one fewer glucose molecule, and the free glucose molecule is in the form of glucose-1-phosphate.
In glycogenolysis, it is the direct product of the reaction in which glycogen phosphorylase cleaves off a molecule of glucose from a greater glycogen structure.

Phosphorylase

phosphorylase bphosphorylasesphosphorylase a
Glycogen phosphorylase is one of the phosphorylase enzymes.
Phosphorylase is also a common name used for glycogen phosphorylase in honor of Earl W. Sutherland Jr. who in the late 1930s discovered the first phosphorylase.

Phosphoglucomutase

EC 5.4.2.2EC 5.4.2.3Phosphoglucomutase deficiency
In order to be used for metabolism, it must be converted to glucose-6-phosphate by the enzyme phosphoglucomutase.
After glycogen phosphorylase catalyzes the phosphorolytic cleavage of a glucosyl residue from the glycogen polymer, the freed glucose has a phosphate group on its 1-carbon.

Glycogen

glycogen depositsglycogen (n)glycogen deposits
Glycogen phosphorylase breaks up glycogen into glucose subunits (see also figure below):
Glycogen phosphorylase is the primary enzyme of glycogen breakdown.

Vitamin B6

vitamin B 6 vitamin B 6 metabolismB 6
Glycogen phosphorylase has a pyridoxal phosphate (PLP, derived from Vitamin B 6 ) at each catalytic site.
PLP is a required coenzyme of glycogen phosphorylase, the enzyme necessary for glycogenolysis to occur.

Pyridoxal phosphate

pyridoxal 5'-phosphatepyridoxal-5'-phosphatePLP
Glycogen phosphorylase has a pyridoxal phosphate (PLP, derived from Vitamin B 6 ) at each catalytic site.
PLP is also found on glycogen phosphorylase in the liver, where it is used to break down glycogen in glycogenolysis when glucagon or epinephrine signals it to do so.

Glycogen storage disease type VI

glycogen storage disease type VIIIHers' diseaseGSD VI
Mutations in the liver isoform of glycogen phosphorylase (PYGL) are associated with Hers' Disease (glycogen storage disease type VI).
Glycogen storage disease type VI (GSD VI) is a type of glycogen storage disease caused by a deficiency in liver glycogen phosphorylase or other components of the associated phosphorylase cascade system.

Glucose 6-phosphate

glucose-6-phosphateG6PD-glucose 6-phosphate
In order to be used for metabolism, it must be converted to glucose-6-phosphate by the enzyme phosphoglucomutase.
When the body needs glucose for energy, glycogen phosphorylase, with the help of an orthophosphate, can cleave away a molecule from the glycogen chain.

Phosphorylase kinase

phosphorylase b kinaseEC 2.7.11.19
PKA phosphorylates phosphorylase kinase, which in turn phosphorylates glycogen phosphorylase b at Ser14, converting it into the active glycogen phosphorylase a.
Phosphorylase kinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen.

Adrenaline

epinephrineadrenaline junkieadrenalin
Hormones such as epinephrine, insulin and glucagon regulate glycogen phosphorylase using second messenger amplification systems linked to G proteins.
Phosphorylase kinase phosphorylates glycogen phosphorylase, which then phosphorylates glycogen and converts it to glucose-6-phosphate.

Glucagon

serum glucagon
Hormones such as epinephrine, insulin and glucagon regulate glycogen phosphorylase using second messenger amplification systems linked to G proteins.
This enzyme, in turn, activates phosphorylase kinase, which then phosphorylates glycogen phosphorylase b (PYG b), converting it into the active form called phosphorylase a (PYG a).

Protein phosphatase 1

PP1protein phosphatase 1 (PP1)Protein Phosphatase-1
Insulin indirectly activates protein phosphatase 1 (PP1) and phosphodiesterase via a signal transduction cascade.
Phosphorylase a serves as a glucose sensor in liver cells.

Protein kinase A

PKAcAMP-dependent protein kinasecyclic AMP-dependent protein kinase
cAMP binds to and activates protein kinase A (PKA).

Glycogen storage disease type V

McArdle's diseaseMcArdle diseaseGlycogenosis type V
Mutations in the muscle isoform of glycogen phosphorylase (PYGM) are associated with glycogen storage disease type V (GSD V, McArdle's Disease).
Genetic sequencing of the PYGM gene (which codes for the muscle isoform of glycogen phosphorylase ) may be done to determine the presence of gene mutations, determining if McArdle's is present.

Calmodulin

CaMcalcium/calmodulincalcium/calmodulin (Ca2+/CaM)
The increased calcium availability binds to the calmodulin subunit and activates glycogen phosphorylase kinase.
Calmodulin plays an important role in the activation of phosphorylase kinase, which ultimately leads to glucose being cleaved from glycogen by glycogen phosphorylase.

Carl Ferdinand Cori

Carl CoriCarlCarl F. Cori
This accomplishment was one of many landmark achievements made by Carl and Gerty Cori.
In St. Louis, the Coris continued their research on glycogen and glucose and began to describe glycogenolysis, identifying and synthesizing the important enzyme glycogen phosphorylase.

Glycogenesis

glycogen synthesisGlycogen biosynthesisglycogenetic
As a result, PKA can no longer initiate the phosphorylation cascade that ends with formation of (active) glycogen phosphorylase a. Overall, insulin signaling decreases glycogenolysis to preserve glycogen stores in the cell and triggers glycogenesis.
Epinephrine not only activates glycogen phosphorylase but also inhibits glycogen synthase.

Enzyme

enzymologyenzymesenzymatic
Glycogen phosphorylase is one of the phosphorylase enzymes.

Phosphorylation

phosphorylatedphosphorylatephosphorylates
Glycogen phosphorylase is also studied as a model protein regulated by both reversible phosphorylation and allosteric effects.

Glucose

dextroseD-glucose D -glucose
Glycogen phosphorylase breaks up glycogen into glucose subunits (see also figure below):

Protein subunit

subunitsubunitsprotein subunits
Glycogen phosphorylase breaks up glycogen into glucose subunits (see also figure below):

Phosphate

phosphatesphosphate groupinorganic phosphate
(α-1,4 glycogen chain) n + Pi ⇌ (α-1,4 glycogen chain) n-1 + α-D-glucose-1-phosphate.

Molecule

molecularmoleculesmolecular structure
Glycogen is left with one fewer glucose molecule, and the free glucose molecule is in the form of glucose-1-phosphate.

Metabolism

metabolicmetabolizedmetabolic pathways
In order to be used for metabolism, it must be converted to glucose-6-phosphate by the enzyme phosphoglucomutase.