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DOPA decarboxylase (aromatic L-amino acid decarboxylase)
Symbol(s): DDC
Locus: 7 p11
EC number
EntrezGene 1644
OMIM 107930
RefSeq NM_000790
UniProt P20711

Aromatic L-amino acid decarboxylase (EC, synonyms: DOPA decarboxylase, tryptophan decarboxylase, 5-hydroxytryptophan decarboxylase, AAAD) is a lyase enzyme.


It catalyzes several different decarboxylation reactions:

The enzyme uses pyridoxal phosphate as a cofactor.

As a rate limiting step

In normal dopamine and serotonin (5-HT) neurotransmitter synthesis, AAAD is not the rate-limiting step in either reaction. However, AAAD becomes the rate-limiting step of dopamine synthesis in patients treated with L-DOPA (such as in Parkinson's Disease), and the rate-limiting step of serotonin synthesis in people treated with 5-HTP (such as in mild depression or dysthymia).

AAAD is the rate-limiting enzyme in the formation of biogenic trace amines.


The gene encoding the enzyme is located on chromosome 7 in humans.[1]

See also

  • Aromatic amino acids


  1. Lisa J. Scherer, John D. McPherson, John J. Wasmuth and J. Lawrence Marsh (June 1992). Human dopa decarboxylase: Localization to human chromosome 7p11 and characterization of hepatic cDNAs. Genomics 13 (2): 469–471.

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