Glycogen phosphorylase, liver form
EC=2.4.1.1
Gene names
Name: PYGL
Organism Homo sapiens (Human) [Reference proteome]
Function
Phosphorylase is an important allosteric enzyme in carbohydrate metabolism. Enzymes from different sources differ in their regulatory mechanisms and in their natural substrates. However, all known phosphorylases share catalytic and structural properties.
Catalytic activity
((1->4)-alpha-D-glucosyl)(n) + phosphate = ((1->4)-alpha-D-glucosyl)(n-1) + alpha-D-glucose 1-phosphate.
Cofactor
Pyridoxal phosphate.
Enzyme regulation
Activity of phosphorylase is controlled both by allosteric means (through the noncovalent binding of metabolites) and by covalent modification. Thus AMP allosterically activates, whereas ATP, ADP, and glucose-6-phosphate allosterically inhibit, phosphorylase B.
Subunit structure
Homodimer. Dimers associate into a tetramer to form the enzymatically active phosphorylase A. Interacts with PPP1R3B By similarity.
Post-translational modification
Phosphorylation of Ser-15 converts phosphorylase B (unphosphorylated) to phosphorylase A.
Involvement in disease
Glycogen storage disease 6 (GSD6) [MIM:232700]: A metabolic disorder characterized by mild to moderate hypoglycemia, mild ketosis, growth retardation, and prominent hepatomegaly. Heart and skeletal muscle are not affected.
Note: The disease is caused by mutations affecting the gene represented in this entry. Ref.4
Sequence similarities
Belongs to the glycogen phosphorylase family.
