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The official name of this gene is “phosphorylase kinase, alpha 1 (muscle).”
PHKA1 is the gene's official symbol. The PHKA1 gene is also known by other names, listed below.
The PHKA1 gene provides instructions for making one piece, the alpha 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 alpha subunit helps regulate the activity of phosphorylase b kinase. 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 alpha-1 subunit produced from the PHKA1 gene is part of the enzyme found in muscle cells.
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 during exercise. 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 six mutations in the PHKA1 gene are known to cause a form of glycogen storage disease type IX (GSD IX) called GSD IXd or X-linked muscle glycogenosis. This form of the disorder is rare and not well understood. It affects muscles and can cause muscle weakness, pain, and cramping, particularly during exercise, although some affected individuals have no signs or symptoms of the condition. Mutations in the PHKA1 gene reduce the activity of phosphorylase b kinase in muscle 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. Reduced energy production in muscle cells leads to the features of GSD IXd.
Cytogenetic Location: Xq12-q13
Molecular Location on the X chromosome: base pairs 71,798,663 to 71,934,028
The PHKA1 gene is located on the long (q) arm of the X chromosome between positions 12 and 13.
More precisely, the PHKA1 gene is located from base pair 71,798,663 to base pair 71,934,028 on the X chromosome.
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 PHKA1 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.
enzyme ; gene ; glucose ; glycogen ; kinase ; simple sugar ; skeletal muscle ; subunit
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://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.