Phosphorylase b kinase gamma catalytic chain, testis/liver isoform is an
enzyme that in humans is encoded by the ''PHKG2''
gene.
The PHKG2 gene provides instructions for making one piece, the gamma subunit, of the phosphorylase b kinase enzyme. This enzyme is made up of 16 subunits, four each of the alpha, beta, gamma, and delta subunits. (Each subunit is produced from a different gene.) The gamma subunit performs the function of phosphorylase b kinase enzyme, and the other subunits help regulate its activity. This enzyme is found in various
tissues, although it is most abundant in the liver and muscles. One version of the enzyme is found in
liver cells and another in
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
cells. The gamma-2 subunit produced from the PHKG2 gene is part of the enzyme found in the liver.
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Phosphorylase b kinase plays an important role in providing energy for cells. The main source of cellular energy is a simple sugar called
glucose. Glucose is stored in muscle and liver cells in a form called
glycogen
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body.
Glycogen functions as one o ...
. Glycogen can be broken down rapidly when glucose is needed, for instance to maintain normal levels of glucose in the blood between meals. Phosphorylase b kinase turns on (activates) another enzyme called
glycogen phosphorylase b by converting it to the more active form,
glycogen phosphorylase a. When active, this enzyme breaks down glycogen.
References
Further reading
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External links
GeneReviews/NCBI/NIH/UW entry on Phosphorylase Kinase Deficiency, Glycogen Storage Disease Type IX
EC 2.7.11
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