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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed April 2012

What is the official name of the PNP gene?

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.

What is the normal function of the PNP gene?

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.

How are changes in the PNP gene related to health conditions?

purine nucleoside phosphorylase deficiency - caused by mutations in the PNP gene

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.

Where is the PNP gene located?

Cytogenetic Location: 14q13.1

Molecular Location on chromosome 14: base pairs 20,469,379 to 20,478,006

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The PNP gene is located on the long (q) arm of chromosome 14 at position 13.1.

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 20,469,379 to base pair 20,478,006 on chromosome 14.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about PNP?

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.

What other names do people use for the PNP gene or gene products?

  • inosine phosphorylase
  • NP
  • PRO1837
  • PUNP
  • purine-nucleoside:orthophosphate ribosyltransferase

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding PNP?

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.


  • Alangari A, Al-Harbi A, Al-Ghonaium A, Santisteban I, Hershfield M. Purine nucleoside phosphorylase deficiency in two unrelated Saudi patients. Ann Saudi Med. 2009 Jul-Aug;29(4):309-12. (
  • Al-Saud B, Alsmadi O, Al-Muhsen S, Al-Ghonaium A, Al-Dhekri H, Arnaout R, Hershfield MS, Al-Mousa H. A novel mutation in purine nucleoside phosphorylase in a child with normal uric acid levels. Clin Biochem. 2009 Nov;42(16-17):1725-7. doi: 10.1016/j.clinbiochem.2009.08.017. Epub 2009 Sep 3. (
  • Aytekin C, Dogu F, Tanir G, Guloglu D, Santisteban I, Hershfield MS, Ikinciogullari A. Purine nucleoside phosphorylase deficiency with fatal course in two sisters. Eur J Pediatr. 2010 Mar;169(3):311-4. doi: 10.1007/s00431-009-1029-6. Epub 2009 Aug 6. (
  • Grunebaum E, Zhang J, Roifman CM. Novel mutations and hot-spots in patients with purine nucleoside phosphorylase deficiency. Nucleosides Nucleotides Nucleic Acids. 2004 Oct;23(8-9):1411-5. Erratum in: Nucleosides Nucleotides Nucleic Acids. 2005;24(4):303. (
  • NCBI Gene (
  • Nyhan WL. Disorders of purine and pyrimidine metabolism. Mol Genet Metab. 2005 Sep-Oct;86(1-2):25-33. Review. (
  • Ozkinay F, Pehlivan S, Onay H, van den Berg P, Vardar F, Koturoglu G, Aksu G, Unal D, Tekgul H, Can S, Ozkinay C. Purine nucleoside phosphorylase deficiency in a patient with spastic paraplegia and recurrent infections. J Child Neurol. 2007 Jun;22(6):741-3. (
  • Walker PL, Corrigan A, Arenas M, Escuredo E, Fairbanks L, Marinaki A. Purine nucleoside phosphorylase deficiency: a mutation update. Nucleosides Nucleotides Nucleic Acids. 2011 Dec;30(12):1243-7. doi: 10.1080/15257770.2011.630852. (


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? ( in the Handbook.

Reviewed: April 2012
Published: February 8, 2016