Aromatic L-amino acid decarboxylase

Aromatic L-amino acid decarboxylase

aromatic-L-amino-acid decarboxylase
Ribbon diagram of a DOPA decarboxylase dimer.[1]
EC number
CAS number 9042-64-2
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
DOPA decarboxylase (aromatic L-amino acid decarboxylase)
Symbol DDC
Entrez 1644
HUGO 2719
OMIM 107930
RefSeq NM_000790
UniProt P20711
Other data
EC number
Locus Chr. 7 p11

Aromatic L-amino acid decarboxylase (EC, synonyms: DOPA decarboxylase, tryptophan decarboxylase, 5-hydroxytryptophan decarboxylase, AAAD,[2] AADC) is a lyase enzyme.


  • Reactions 1
  • As a rate-limiting step 2
  • Genetics 3
  • See also 4
  • References 5
  • External links 6


It catalyzes several different decarboxylation reactions:[3]

The enzyme uses pyridoxal phosphate, the active form of vitamin B6, as a cofactor.

Human biosynthesis pathway for trace amines and catecholamines[4][5]
In humans, catecholamines and phenethylaminergic trace amines are derived from the amino acid phenylalanine.
Human serotonin biosynthesis pathway

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 inhibited by Carbidopa outside of the blood brain barrier to inhibit the premature conversion of L-DOPA to Dopamine in the treatment of Parkinson's.

In humans, AAAD is also the rate-limiting enzyme in the formation of trace amine neurotransmitters.


The gene encoding the enzyme is referred to as DDC and located on chromosome 7 in humans.[6] Single nucleotide polymorphisms and other gene variations have been investigated in relation to neuropsychiatric disorders, e.g., a one-base pair deletion at –601 and a four-base pair deletion at 722–725 in exon 1 in relation to bipolar disorder[7] and autism. No direct correlation between gene variation and autism was found.[8]

See also


  1. ^ ​; Burkhard P, Dominici P, Borri-Voltattorni C, Jansonius JN, Malashkevich VN (November 2001). "Structural insight into Parkinson's disease treatment from drug-inhibited DOPA decarboxylase". Nat. Struct. Biol. 8 (11): 963–7.  
  2. ^ Logan, Carolynn M.; Rice, M. Katherine (1987). Logan's Medical and Scientific Abbreviations. Philadelphia:  
  3. ^ "AADC". Human Metabolome database. Retrieved 17 February 2015. 
  4. ^ Broadley KJ (March 2010). "The vascular effects of trace amines and amphetamines". Pharmacol. Ther. 125 (3): 363–375.  
  5. ^ Lindemann L, Hoener MC (May 2005). "A renaissance in trace amines inspired by a novel GPCR family". Trends Pharmacol. Sci. 26 (5): 274–281.  
  6. ^ 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".  
  7. ^ A. D. Borglum, T. G. Bruun, T. E. Kjeldsen, H. Ewald, O. Mors, G. Kirov, C. Russ, B. Freeman, D. A. Collier & T. A. Kruse (November 1999). "Two novel variants in the DOPA decarboxylase gene: association with bipolar affective disorder".  
  8. ^ Marlene B. Lauritsen, Anders D. Borglum, Catalina Betancur, Anne Philippe, Torben A. Kruse, Marion Leboyer & Henrik Ewald (May 2002). "Investigation of two variants in the DOPA decarboxylase gene in patients with autism".  

External links