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The official name of this gene is “purine nucleoside phosphorylase.”
PNP is the gene's official symbol. The PNP gene is also known by other names, listed below.
The PNP gene provides instructions for making an enzyme called purine nucleoside phosphorylase. This enzyme is found throughout the body but is most active in specialized white blood cells called lymphocytes. These cells protect the body against potentially harmful invaders by making immune proteins called antibodies that tag foreign particles and germs for destruction or by directly attacking virus-infected cells. Lymphocytes are produced in specialized lymphoid tissues including the thymus and lymph nodes, and then released into the blood. The thymus is a gland located behind the breastbone; lymph nodes are found throughout the body. Lymphocytes in the blood and in lymphoid tissues make up the immune system.
Purine nucleoside phosphorylase is known as a housekeeping enzyme because it clears away waste molecules called deoxyinosine and deoxyguanosine, which are generated when DNA is broken down. Specifically, purine nucleoside phosphorylase converts deoxyinosine to another molecule called hypoxanthine, and converts deoxyguanosine to another molecule called guanine.
At least 24 PNP gene mutations have been identified in individuals with purine nucleoside phosphorylase deficiency. Most of these mutations change single protein building blocks (amino acids) in the purine nucleoside phosphorylase enzyme. The mutations reduce or eliminate the activity of purine nucleoside phosphorylase. The resulting excess of waste molecules and further reactions involving them lead to the buildup of a substance called deoxyguanosine triphosphate (dGTP) to levels that are toxic to lymphocytes.
Immature lymphocytes in the thymus are particularly vulnerable to a toxic buildup of dGTP, which damages them and triggers their self-destruction (apoptosis). The number of lymphocytes in other lymphoid tissues is also greatly reduced, resulting in the immune deficiency and vulnerability to severe infections characteristic of purine nucleoside phosphorylase deficiency.
Cytogenetic Location: 14q13.1
Molecular Location on chromosome 14: base pairs 20,937,537 to 20,946,164
The PNP gene is located on the long (q) arm of chromosome 14 at position 13.1.
More precisely, the PNP gene is located from base pair 20,937,537 to base pair 20,946,164 on chromosome 14.
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 PNP 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.
acids ; apoptosis ; deficiency ; DNA ; enzyme ; gene ; guanine ; immune system ; lymph ; lymphoid ; molecule ; nucleoside ; protein ; thymus ; toxic ; virus ; white blood cells
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.