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glycogen phosphorylase
Function:
- allosteric enzyme in carbohydrate metabolism
- catalyzes formation of glucose-1-phosphate from glycogen during glycogenolysis
- enzymes from different sources differ in their regulatory mechanisms & in their natural substrates
- all known phosphorylases share catalytic & structural properties
- activity of phosphorylase is controlled both by allosteric means (through the noncovalent binding of metabolites) & by covalent modification
- AMP allosterically activates, whereas ATP, ADP, & glucose-6-phosphate allosterically inhibit
- phosphorylation by phosphorylase kinase activates
(1,4-alpha-D-glucosyl)(n)* + phosphate
(1,4-alpha-D-glucosyl)(n-1)* + alpha-D glucose-1-phosphate
* glycogen
Cofactor: pyridoxal phosphate
Pathology:
- defects associated with glycogen storage disease type V (McArdle Disease)
Laboratory:
- phosphorylase in erythrocytes
Interactions
molecular events
Specific
phosphorylase-A
phosphorylase-B (brain glycogen phosphorylase, PYGB)
phosphorylase-L (liver glycogen phosphorylase, PYGL)
phosphorylase-M (myophosphorylase, muscle glycogen phosphorylase, PYGM)
General
hexosyltransferase
oligomerizing protein
phosphoprotein
phosphotransferase
regulatory molecule
Properties
CONFIGURATION: dimer
SIZE: MW = 97 kD
COMPARTMENT: cytoplasm
MOTIF: Ser phosphorylation site {S14}
kinase domain
MOTIF: ATP-binding site
NAME: ATP-binding site
cofactor-binding site
COFACTOR-BOUND: pyridoxal phosphate
Database Correlations
ENZYME 2.4.1.1
References
- Textbook of Biochemistry with Clinical Correlations,
3rd ed., TM Devlin (ed), Wiley-Liss, NY 1992 pg 346
- Wikipedia: Glycogen phosphorylase
https://en.wikipedia.org/wiki/Glycogen_phosphorylase