Phosphorylase b kinase gamma catalytic chain, testis/liver isoform is an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
that in humans is encoded by the ''PHKG2''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
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
The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
cells and another in
muscle cells. The gamma-2 subunit produced from the PHKG2 gene is part of the enzyme found in the liver.
[ ]
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 a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
. Glucose is stored in muscle and liver cells in a form called
glycogen. 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
*
*
*
*
*
*
*
*
*
*
*
*
External links
GeneReviews/NCBI/NIH/UW entry on Phosphorylase Kinase Deficiency, Glycogen Storage Disease Type IX
EC 2.7.11
{{protein-stub