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


Reviewed July 2011

What is the official name of the QDPR gene?

The official name of this gene is “quinoid dihydropteridine reductase.”

QDPR is the gene's official symbol. The QDPR gene is also known by other names, listed below.

What is the normal function of the QDPR gene?

The QDPR gene provides instructions for making an enzyme called quinoid dihydropteridine reductase. This enzyme helps carry out one step in the chemical pathway that recycles a molecule called tetrahydrobiopterin (BH4).

Tetrahydrobiopterin plays a critical role in processing several protein building blocks (amino acids) in the body. For example, it works with the enzyme phenylalanine hydroxylase to convert an amino acid called phenylalanine into another amino acid, tyrosine. Tetrahydrobiopterin is also involved in reactions that produce chemicals called neurotransmitters, which transmit signals between nerve cells in the brain. Because it helps enzymes carry out chemical reactions, tetrahydrobiopterin is known as a cofactor.

When tetrahydrobiopterin interacts with enzymes during chemical reactions, the cofactor is altered and must be recycled to a usable form. Quinoid dihydropteridine reductase is one of two enzymes that help recycle tetrahydrobiopterin in the body.

Does the QDPR gene share characteristics with other genes?

The QDPR gene belongs to a family of genes called SDR (short chain dehydrogenase/reductase superfamily).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? ( in the Handbook.

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

tetrahydrobiopterin deficiency - caused by mutations in the QDPR gene

More than 30 mutations in the QDPR gene have been found to cause tetrahydrobiopterin deficiency. When this condition results from QDPR gene mutations, it is known as dihydropteridine reductase (DHPR) deficiency. DHPR deficiency accounts for about one-third of all cases of tetrahydrobiopterin deficiency.

Most QDPR gene mutations change single amino acids in quinoid dihydropteridine reductase, although some mutations insert small amounts of DNA into the QDPR gene or disrupt the way the gene's instructions are used to make the enzyme. Changes in quinoid dihydropteridine reductase greatly reduce or eliminate the enzyme's activity. Without enough of this enzyme, tetrahydrobiopterin is not recycled properly. As a result, this cofactor is not available to participate in chemical reactions such as the conversion of phenylalanine to tyrosine. If phenylalanine is not converted to tyrosine, it can build up to toxic levels in the blood and other tissues. Nerve cells in the brain are particularly sensitive to phenylalanine levels, which is why excessive amounts of this substance can cause brain damage.

Additionally, a reduction in quinoid dihydropteridine reductase activity disrupts the production of certain neurotransmitters in the brain. Because neurotransmitters are necessary for normal brain function, changes in the levels of these brain chemicals contribute to intellectual disability in people with DHPR deficiency.

Where is the QDPR gene located?

Cytogenetic Location: 4p15.31

Molecular Location on chromosome 4: base pairs 17,486,392 to 17,512,233

The QDPR gene is located on the short (p) arm of chromosome 4 at position 15.31.

The QDPR gene is located on the short (p) arm of chromosome 4 at position 15.31.

More precisely, the QDPR gene is located from base pair 17,486,392 to base pair 17,512,233 on chromosome 4.

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

Where can I find additional information about QDPR?

You and your healthcare professional may find the following resources about QDPR 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 QDPR gene or gene products?

  • DHPR
  • Dihydropteridine reductase
  • PKU2
  • SDR33C1

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

What glossary definitions help with understanding QDPR?

acids ; amino acid ; cofactor ; deficiency ; disability ; DNA ; enzyme ; gene ; molecule ; neurotransmitters ; phenylalanine ; protein ; toxic ; tyrosine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (


  • Dianzani I, de Sanctis L, Smooker PM, Gough TJ, Alliaudi C, Brusco A, Spada M, Blau N, Dobos M, Zhang HP, Yang N, Ponzone A, Armarego WL, Cotton RG. Dihydropteridine reductase deficiency: physical structure of the QDPR gene, identification of two new mutations and genotype-phenotype correlations. Hum Mutat. 1998;12(4):267-73. (
  • Longo N. Disorders of biopterin metabolism. J Inherit Metab Dis. 2009 Jun;32(3):333-42. doi: 10.1007/s10545-009-1067-2. Epub 2009 Feb 9. Review. Erratum in: J Inherit Metab Dis. 2009 Jun;32(3):457. (
  • NCBI Gene (
  • Ponzone A, Spada M, Ferraris S, Dianzani I, de Sanctis L. Dihydropteridine reductase deficiency in man: from biology to treatment. Med Res Rev. 2004 Mar;24(2):127-50. Review. (
  • Romstad A, Kalkanoğlu HS, Coşkun T, Demirkol M, Tokatli A, Dursun A, Baykal T, Ozalp I, Guldberg P, Güttler F. Molecular analysis of 16 Turkish families with DHPR deficiency using denaturing gradient gel electrophoresis (DGGE). Hum Genet. 2000 Dec;107(6):546-53. (
  • Shintaku H. Disorders of tetrahydrobiopterin metabolism and their treatment. Curr Drug Metab. 2002 Apr;3(2):123-31. Review. (
  • Thöny B, Auerbach G, Blau N. Tetrahydrobiopterin biosynthesis, regeneration and functions. Biochem J. 2000 Apr 1;347 Pt 1:1-16. Review. (
  • Thöny B, Blau N. Mutations in the BH4-metabolizing genes GTP cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase, sepiapterin reductase, carbinolamine-4a-dehydratase, and dihydropteridine reductase. Hum Mutat. 2006 Sep;27(9):870-8. (


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: July 2011
Published: March 23, 2015