DDC (Aromatic L-amino acid decarboxylase, DOPA decarboxylase, AADC, AAAD) is a lyase that catalyzes the decarboxylation reactions for a number of neurotransmitters and neuromodulators including dopamine, serotonin, histamine and phenylalanine. DDC is required for normal neural function. It can also be a rate-limiting step in dopamine and serotonin synthesis, specifically in Parkinson’s disease patients treated with L-DOPA and in dysthymia or depression patients treated with 5-HTP. Deficiency of DDC is associated with developmental delay, autonomic dysfunction and oculogyric crises, and inherited polymorphisms in DDC may contribute to various neuropsychiatric phenotypes and conditions. In immunohistochemistry of normal tissue, DDC has highest cytoplasmic positivity in renal tissues and is also found in the cerebral cortex, appendix, lung, liver, gastrointestinal tract, prostate, breast and in endocrine and reproductive tissues. References: BioMed Research International. 2013. Volume 2013 (161456), DOI:10.1155/2013/161456; Neuropsychopharmacology. 2016 Aug; 41(9): 2303–2308; 26924680;