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purine nucleoside phosphorylase

  • genes

1. Introduction

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 certain white blood cells called lymphocytes. These cells protect the body against potentially harmful invaders, such as bacteria or viruses. 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 are a major component of 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.

Health Conditions Related to Genetic Changes

2. Purine nucleoside phosphorylase deficiency

More than 35 PNP gene mutations have been identified in individuals with purine nucleoside phosphorylase deficiency, which is an immune system disorder in which the body is unable to fight foreign invaders such as bacteria and viruses. Affected individuals have repeated infections that can be life-threatening. Some people with purine nucleoside phosphorylase deficiency also have neurological problems, such as intellectual disability or difficulty coordinating movements (ataxia).

Most of the PNP gene 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.

A type of lymphocytes known as T cells are particularly vulnerable to a toxic buildup of dGTP, particularly immature T cells in the thymus. The dGTP damages these cells and triggers their self-destruction (apoptosis). Lymphocytes in other lymphoid tissues can also be damaged. The shortage of lymphocytes results in the immune problems that cause vulnerability to severe infections. Damage to brain cells caused by buildup of dGTP is thought to underlie the neurological problems that occur in some people with purine nucleoside phosphorylase deficiency.

3. Other Names for This Gene

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


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  2. Aytekin C, Dogu F, Tanir G, Guloglu D, Santisteban I, Hershfield MS,Ikinciogullari A. Purine nucleoside phosphorylase deficiency with fatal course intwo sisters. Eur J Pediatr. 2010 Mar;169(3):311-4. doi:10.1007/s00431-009-1029-6.
  3. Fekrvand S, Yazdani R, Abolhassani H, Ghaffari J, Aghamohammadi A. The FirstPurine Nucleoside Phosphorylase Deficiency Patient Resembling IgA Deficiency and a Review of the Literature. Immunol Invest. 2019 May;48(4):410-430. doi:10.1080/08820139.2019.1570249.
  4. Grunebaum E, Zhang J, Roifman CM. Novel mutations and hot-spots in patientswith purine nucleoside phosphorylase deficiency. Nucleosides Nucleotides Nucleic Acids. 2004 Oct;23(8-9):1411-5. Erratum in: Nucleosides Nucleotides NucleicAcids. 2005;24(4):303.
  5. Nyhan WL. Disorders of purine and pyrimidine metabolism. Mol Genet Metab. 2005Sep-Oct;86(1-2):25-33. Review.
  6. 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 ina patient with spastic paraplegia and recurrent infections. J Child Neurol. 2007 Jun;22(6):741-3.
  7. Somech R, Lev A, Grisaru-Soen G, Shiran SI, Simon AJ, Grunebaum E. Purinenucleoside phosphorylase deficiency presenting as severe combined immunedeficiency. Immunol Res. 2013 May;56(1):150-4. doi: 10.1007/s12026-012-8380-9.
  8. Walker PL, Corrigan A, Arenas M, Escuredo E, Fairbanks L, Marinaki A. Purinenucleoside phosphorylase deficiency: a mutation update. Nucleosides NucleotidesNucleic Acids. 2011 Dec;30(12):1243-7. doi: 10.1080/15257770.2011.630852.
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Entry Collection: MedlinePlus
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Update Time: 25 Dec 2020
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    Guo, L.Y. PNP Gene. Encyclopedia. Available online: (accessed on 15 August 2022).
    Guo LY. PNP Gene. Encyclopedia. Available at: Accessed August 15, 2022.
    Guo, Lily Yueming. "PNP Gene," Encyclopedia, (accessed August 15, 2022).
    Guo, L.Y. (2020, December 25). PNP Gene. In Encyclopedia.
    Guo, Lily Yueming. ''PNP Gene.'' Encyclopedia. Web. 25 December, 2020.