Phosphorylase kinase

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

Genes

 * Alpha: ,
 * Beta:
 * Gamma: ,

Structure
Phosphorylase kinase contain 4 calcium ion binding site.

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-bound and the sigma subunit is phosphorylated at the same time.