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The official name of this gene is “phosphorylase kinase, gamma 2 (testis).”
PHKG2 is the gene's official symbol. The PHKG2 gene is also known by other names, listed below.
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 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 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.
At least 13 mutations in the PHKG2 gene are known to cause a form of glycogen storage disease type IX (GSD IX) called GSD IXc. This form of the disorder affects liver function and causes an enlarged liver (hepatomegaly), slow growth, and periods of low blood sugar (hypoglycemia) in affected individuals. These features usually improve over time. However, PHKG2 gene mutations have been associated with more severe signs and symptoms such as irreversible liver disease (cirrhosis).
Mutations in the PHKG2 gene reduce the activity of phosphorylase b kinase in liver cells, although the mechanism is unknown. Reduction of this enzyme's function impairs glycogen breakdown. As a result, glycogen builds up in cells, and glucose is not available for energy. The inability to break down glycogen in the liver causes the features of GSD IXc.
Cytogenetic Location: 16p11.2
Molecular Location on chromosome 16: base pairs 30,748,252 to 30,761,175
The PHKG2 gene is located on the short (p) arm of chromosome 16 at position 11.2.
More precisely, the PHKG2 gene is located from base pair 30,748,252 to base pair 30,761,175 on chromosome 16.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about PHKG2 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
breakdown ; catalytic ; cirrhosis ; domain ; enzyme ; gene ; glucose ; glycogen ; hypoglycemia ; kinase ; muscle cells ; protein ; serine ; simple sugar ; subunit ; testis ; threonine
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.