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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 PCBD1 gene?

The official name of this gene is “pterin-4 alpha-carbinolamine dehydratase 1.”

PCBD1 is the gene's official symbol. The PCBD1 gene is also known by other names, listed below.

What is the normal function of the PCBD1 gene?

The PCBD1 gene provides instructions for making an enzyme called pterin-4 alpha-carbinolamine dehydratase. 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. Pterin-4 alpha-carbinolamine dehydratase is one of two enzymes that help recycle tetrahydrobiopterin in the body.

How are changes in the PCBD1 gene related to health conditions?

tetrahydrobiopterin deficiency - caused by mutations in the PCBD1 gene

At least nine mutations in the PCBD1 gene have been found to cause tetrahydrobiopterin deficiency. When this condition results from PCBD1 gene mutations, it is known as pterin-4 alpha-carbinolamine dehydratase (PCD) deficiency. PCD deficiency accounts for about 5 percent of all cases of tetrahydrobiopterin deficiency.

Some mutations in the PCBD1 gene change single amino acids in pterin-4 alpha-carbinolamine dehydratase, while other mutations introduce a premature stop signal in the instructions for making this enzyme. Changes in pterin-4 alpha-carbinolamine dehydratase reduce the enzyme's activity, which affects the body's ability to recycle tetrahydrobiopterin. As a result, less of this cofactor is available to participate in chemical reactions such as the conversion of phenylalanine to tyrosine. If phenylalanine is not converted to tyrosine, the excess can build up in the bloodstream and other tissues.

Although people with PCD deficiency usually have elevated levels of phenylalanine in the blood, this form of tetrahydrobiopterin deficiency rarely causes significant medical problems. Researchers believe that other enzymes may compensate for the reduced activity of pterin-4 alpha-carbinolamine dehydratase in people with PCBD1 gene mutations.

Where is the PCBD1 gene located?

Cytogenetic Location: 10q22

Molecular Location on chromosome 10: base pairs 70,882,280 to 70,888,786

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

The PCBD1 gene is located on the long (q) arm of chromosome 10 at position 22.

The PCBD1 gene is located on the long (q) arm of chromosome 10 at position 22.

More precisely, the PCBD1 gene is located from base pair 70,882,280 to base pair 70,888,786 on chromosome 10.

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

Where can I find additional information about PCBD1?

You and your healthcare professional may find the following resources about PCBD1 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 PCBD1 gene or gene products?

  • 4-alpha-hydroxy-tetrahydropterin dehydratase
  • 6-pyruvoyl-tetrahydropterin synthase/dimerization cofactor of hepatocyte nuclear factor 1 alpha (TCF1)
  • Carbinolamine-4a-dehydratase
  • DCOH
  • Dimerization cofactor of hepatocyte nuclear factor 1-alpha
  • Dimerization cofactor of HNF1
  • PCBD
  • PCD
  • Phenylalanine hydroxylase-stimulating protein
  • Pterin-4a-carbinolamine dehydratase (dimerization cofactor of hepatic nuclear factor 1-alpha)
  • Pterin-4-alpha-carbinolamine dehydratase
  • pterin-4 alpha-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor 1 alpha
  • pterin-4 alpha-carbinolamine dehydratase/dimerization cofactor of hepatocyte nuclear factor 1 alpha (TCF1)
  • Pterin carbinolamine dehydratase

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

What glossary definitions help with understanding PCBD1?

acids ; amino acid ; cofactor ; deficiency ; enzyme ; gene ; hepatic ; molecule ; neurotransmitters ; phenylalanine ; protein ; tyrosine

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


  • Citron BA, Kaufman S, Milstien S, Naylor EW, Greene CL, Davis MD. Mutation in the 4a-carbinolamine dehydratase gene leads to mild hyperphenylalaninemia with defective cofactor metabolism. Am J Hum Genet. 1993 Sep;53(3):768-74. (
  • 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 (
  • 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. (
  • Thöny B, Neuheiser F, Kierat L, Rolland MO, Guibaud P, Schlüter T, Germann R, Heidenreich RA, Duran M, de Klerk JB, Ayling JE, Blau N. Mutations in the pterin-4alpha-carbinolamine dehydratase (PCBD) gene cause a benign form of hyperphenylalaninemia. Hum Genet. 1998 Aug;103(2):162-7. (


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: February 8, 2016