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DDC gene

dopa decarboxylase

Normal Function

The DDC gene provides instructions for making the aromatic l-amino acid decarboxylase (AADC) enzyme, which is important in the brain and nervous system. This enzyme takes part in the pathway that produces dopamine and serotonin, which are chemical messengers that transmit signals between nerve cells (neurotransmitters).

Dopamine is produced from the protein building block (amino acid) tyrosine, and serotonin is produced from the amino acid tryptophan. Both neurotransmitters are produced in two-step processes. First, other enzymes control the reactions that convert tyrosine to L-dopa, and tryptophan to 5-hydroxytryptophan. The AADC enzyme then converts L-dopa and 5-hydroxytryptophan to dopamine and serotonin, respectively. To do this, it removes a molecular structure called a carboxyl group, consisting of a carbon atom, two oxygen atoms, and a hydrogen atom.

Health Conditions Related to Genetic Changes

Aromatic l-amino acid decarboxylase deficiency

Mutations in the DDC gene result in reduced activity of the AADC enzyme. Without enough of this enzyme, nerve cells produce less dopamine and serotonin. Dopamine and serotonin are necessary for normal nervous system function, and changes in the levels of these neurotransmitters contribute to the developmental delay, intellectual disability, abnormal movements, and autonomic dysfunction seen in people with AADC deficiency.

More About This Health Condition

Other disorders

Studies have shown certain variations (polymorphisms) in the DDC gene to be associated with increased risk of nicotine dependence, schizophrenia, bipolar disorder, and attention-deficit/hyperactivity disorder (ADHD); however, other studies have not supported these findings. Many genetic and environmental factors are believed to contribute to these complex conditions.

Other Names for This Gene

  • AADC
  • aromatic L-amino acid decarboxylase
  • dopa decarboxylase (aromatic L-amino acid decarboxylase)

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


  • Hyland K, Surtees RA, Rodeck C, Clayton PT. Aromatic L-amino acid decarboxylase deficiency: clinical features, diagnosis, and treatment of a new inborn error of neurotransmitter amine synthesis. Neurology. 1992 Oct;42(10):1980-8. doi: 10.1212/wnl.42.10.1980. Citation on PubMed
  • Hyland K. Inherited disorders affecting dopamine and serotonin: critical neurotransmitters derived from aromatic amino acids. J Nutr. 2007 Jun;137(6 Suppl 1):1568S-1572S; discussion 1573S-1575S. doi: 10.1093/jn/137.6.1568S. Citation on PubMed
  • Pearl PL, Capp PK, Novotny EJ, Gibson KM. Inherited disorders of neurotransmitters in children and adults. Clin Biochem. 2005 Dec;38(12):1051-8. doi: 10.1016/j.clinbiochem.2005.09.012. Epub 2005 Nov 18. Citation on PubMed
  • Pearl PL, Taylor JL, Trzcinski S, Sokohl A. The pediatric neurotransmitter disorders. J Child Neurol. 2007 May;22(5):606-16. doi: 10.1177/0883073807302619. Citation on PubMed
  • Verbeek MM, Geurtz PB, Willemsen MA, Wevers RA. Aromatic L-amino acid decarboxylase enzyme activity in deficient patients and heterozygotes. Mol Genet Metab. 2007 Apr;90(4):363-9. doi: 10.1016/j.ymgme.2006.12.001. Epub 2007 Jan 19. Citation on PubMed
  • Yu Y, Panhuysen C, Kranzler HR, Hesselbrock V, Rounsaville B, Weiss R, Brady K, Farrer LA, Gelernter J. Intronic variants in the dopa decarboxylase (DDC) gene are associated with smoking behavior in European-Americans and African-Americans. Hum Mol Genet. 2006 Jul 15;15(14):2192-9. doi: 10.1093/hmg/ddl144. Epub 2006 Jun 1. Citation on PubMed
  • Zhang H, Ye Y, Wang X, Gelernter J, Ma JZ, Li MD. DOPA decarboxylase gene is associated with nicotine dependence. Pharmacogenomics. 2006 Dec;7(8):1159-66. doi: 10.2217/14622416.7.8.1159. 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.