DOPA decarboxylase (DDC), also known as aromatic L-amino acid decarboxylase (AADC), is the final enzyme in the biosynthesis of dopamine and serotonin. It catalyzes the decarboxylation of L-DOPA to dopamine and 5-hydroxytryptophan to serotonin [1,2]. In addition, it is responsible for the synthesis of the trace amines phenylethylamine, p-tyramine, and tryptamine, which are considered to act as neuromodulators [3].
DDC is expressed in both neuronal and non-neuronal tissues, including the brain, liver, kidney, small intestine, ovary, and peripheral blood vessels. Tissue-specific expression is regulated by distinct neuronal and non-neuronal promoters, producing transcript isoforms with differences in their 5′ untranslated regions and alternative exons [1,4].
DDC has a central role in neurotransmitter biosynthesis and is therefore essential for dopaminergic and serotonergic signaling. In Parkinson’s disease, DDC is particularly important by mediating parts of the therapeutic effect of L-DOPA treatment [2,5]. Alterations in DDC activity or expression may influence the response to therapy and disease-associated neurotransmitter metabolism [2,6]. Evidence also suggests that altered circulating DDC activity may have potential as a biomarker for Parkinson’s disease [7].
