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PNPO gene

pyridoxamine 5'-phosphate oxidase

Normal Function

The PNPO gene provides instructions for producing an enzyme called pyridoxine 5'-phosphate oxidase. This enzyme is involved in the breakdown (metabolism) of vitamin B6. Specifically, it chemically modifies two forms of vitamin B6 derived from food (pyridoxine and pyridoxamine) to form pyridoxal 5'-phosphate (PLP). PLP is the active form of vitamin B6 and is necessary for many processes in the body, including protein metabolism and the production of chemicals that transmit signals in the brain (neurotransmitters). Pyridoxine 5'-phosphate oxidase is active (expressed) in cells throughout the body, with the highest amounts found in the liver.

Health Conditions Related to Genetic Changes

Pyridoxal 5'-phosphate-dependent epilepsy

At least 7 mutations in the PNPO gene have been found to cause pyridoxal 5'-phosphate-dependent epilepsy. Most of these mutations change one protein building block (amino acid) in the pyridoxine 5'-phosphate oxidase enzyme, impairing its normal function. The resulting enzyme cannot effectively metabolize pyridoxine and pyridoxamine to produce PLP. A shortage of PLP can disrupt the function of many other proteins and enzymes that need PLP in order to be effective. It is not clear how the lack of PLP affects the brain and leads to the seizures that are characteristic of this condition.

More About This Health Condition

Other Names for This Gene

  • FLJ10535
  • pyridoxine 5'-phosphate oxidase

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Kang JH, Hong ML, Kim DW, Park J, Kang TC, Won MH, Baek NI, Moon BJ, Choi SY, Kwon OS. Genomic organization, tissue distribution and deletion mutation of human pyridoxine 5'-phosphate oxidase. Eur J Biochem. 2004 Jun;271(12):2452-61. doi: 10.1111/j.1432-1033.2004.04175.x. Citation on PubMed
  • Mills PB, Surtees RA, Champion MP, Beesley CE, Dalton N, Scambler PJ, Heales SJ, Briddon A, Scheimberg I, Hoffmann GF, Zschocke J, Clayton PT. Neonatal epileptic encephalopathy caused by mutations in the PNPO gene encoding pyridox(am)ine 5'-phosphate oxidase. Hum Mol Genet. 2005 Apr 15;14(8):1077-86. doi: 10.1093/hmg/ddi120. Epub 2005 Mar 16. Citation on PubMed
  • Musayev FN, Di Salvo ML, Ko TP, Schirch V, Safo MK. Structure and properties of recombinant human pyridoxine 5'-phosphate oxidase. Protein Sci. 2003 Jul;12(7):1455-63. doi: 10.1110/ps.0356203. Citation on PubMed or Free article on PubMed Central
  • Plecko B, Mills P. PNPO Deficiency. 2022 Jun 23. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2023. Available from Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.