Phosphorylase kinase

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Phosphorylase kinase is a serine/threonine-specific protein kinase which converts phosphorylase b to Phosphorylase a. One of the enzyme activated by this enzyme is glycogen phosphorylase

Contents 1 Genes 2 Structure 3 Regulation 4 See also 5 External links

[edit] Genes

• Alpha: PHKA1, PHKA2
• Beta: PHKB
• Gamma: PHKG1, PHKG2

[edit] Structure

Phosphorylase kinase contain 4 subunits: alpha, beta, gamma and sigma subunits. The beta subunit contain the phosphorylation site when the sigma subunit contain the calcium ion binding site.

[edit] Regulation

The enzyme is regulated by both allosteric regulation and reversible phosphorylation.

Hormones, nerve impulses and muscle contraction stimulate the release of calcium ions; the allosteric activator, calcium ions bind to the beta subunits of the enzymes and partly activiate the enzyme activities.

Hormones also stimulate the phosphorylation of Protein Kinase A, which catalyse the phosphorylation of sigma subunits on the phosphorylase kinases; the phosphorylation partly activate the activities of the enzymes.

The phosphorylase kinase is competely activated when the beta subunit is calcium-ion-binded and the sigma subunit is phosphorylated at the same time.

[edit] See also

• calmodulin
• glycogenolysis

[edit] External links

• EC 2.7.11.19
• MeSH Phosphorylase+kinase
• Overview at ox.ac.uk
• Nadeau O, Gogol E, Carlson G (2005). "Cryoelectron microscopy reveals new features in the three-dimensional structure of phosphorylase kinase.". Protein Sci 14 (4): 914-20. PMID 15741332. 
• Brushia R, Walsh D (1999). "Phosphorylase kinase: the complexity of its regulation is reflected in the complexity of its structure.". Front Biosci 4: D618-41. PMID 10487978.