glycogen phosphorylase (PYGM) dimer b + 2 ATP => glycogen phosphorylase (PYGM) dimer a + 2 ADP

Stable Identifier
Reaction [transition]
Homo sapiens
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The cytosolic phosphorylase kinase complex catalyzes the phosphorylation of the subunits of the glycogen phosphorylase (PYGM) dimer. Two forms of phosphorylase kinase complex have been described (Brushia and Walsh 1999). The one annotated here, consisting of four copies each of PHKA1 (alpha regulatory) (Burwinkel et al 2003), PHKB (beta regulatory) (Burwinkel et al. 2003), PHKG1 (gamma catalytic) (Burwinkel et al. 2003) and CALM (calmodulin) subunits is abundant in muscle and its action on the form of phosphorylase (PYGM) abundant in muscle is described.

While initial studies of PGYM from rabbit muscle suggested that it is a homotetramer (Keller and Cori 1953), more recent work indicates that under physiological conditions the enzyme occurs as a homodimer (Huang and Graves 1970) and a dimeric structure for the human enzyme is inferred here.

Literature References
PubMed ID Title Journal Year
13115432 Enzymic conversion of phosphorylase a to phosphorylase b

Cori, GT, Keller, PJ

Biochim Biophys Acta 1953
10487978 Phosphorylase kinase: the complexity of its regulation is reflected in the complexity of its structure

Walsh, DA, Brushia, RJ

Front Biosci 1999
5461220 Correlation between subunit interactions and enzymatic activity of phosphorylase a. Method for determining equilibrium constants from initial rate measurements

Huang, CY, Graves, DJ

Biochemistry 1970
12825073 Muscle glycogenosis with low phosphorylase kinase activity: mutations in PHKA1, PHKG1 or six other candidate genes explain only a minority of cases

Vorgerd, M, Kilimann, MW, Moses, SW, Schroers, A, Clemens, PR, Shin, YS, Burwinkel, B, Pongratz, D, Hu, B

Eur J Hum Genet 2003
Catalyst Activity

phosphorylase kinase activity of phosphorylase kinase complex (PHKM) [cytosol]

This event is regulated
Positively by
Orthologous Events
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