Skip navigation

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

URL of this page: https://medlineplus.gov/genetics/gene/pnpo/

PNPO gene

pyridoxamine 5'-phosphate oxidase

Normal Function

The PNPO gene provides instructions for producing an enzyme called pyridox(am)ine 5'-phosphate oxidase. This enzyme is involved in the breakdown (metabolism) of vitamin B6. Specifically, it chemically modifies two forms of vitamin B6 obtained from food (pyridoxine and pyridoxamine) to create pyridoxal 5'-phosphate (PLP). PLP is the active form of vitamin B6, and it is necessary for many chemical reactions in the body, including protein metabolism and the processing of chemicals that transmit signals in the brain (neurotransmitters). Pyridox(am)ine 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 phosphate-responsive seizures

Several variants (also called mutations) in the PNPO gene have been found to cause pyridoxal phosphate-responsive seizures (sometimes called pyridoxamine 5'-phosphate oxidase deficiency or PNPO deficiency). People with PNPO deficiency typically develop seizures shortly after birth. Most of the variants in the PNPO gene that cause PNPO deficiency change one protein building block (amino acid) in the pyridox(am)ine 5'-phosphate oxidase enzyme, impairing its normal function. The resulting enzyme cannot effectively metabolize vitamin B6 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 Because PLP plays an important role in neurotransmitter metabolism, a lack of PLP is believed to cause the seizures that are characteristic of PNPO deficiency. 

More About This Health Condition

Other Names for This Gene

  • HEL-S-302
  • PDXPO
  • pyridoxal 5-prime-phosphate oxidase
  • pyridoxal 5-prime-phosphate synthetase
  • pyridoxamine-phosphate oxidase
  • 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

References

  • 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, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from http://www.ncbi.nlm.nih.gov/books/NBK581452/ 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.