Catalyzes the decarboxylation of L-3,4-dihydroxyphenylalanine (DOPA) to dopamine, L-5-hydroxytryptophan to serotonin and L-tryptophan to tryptamine. Variation in the synthesis of bioamines may be a factor contributing to natural variation in life span. H(+) + L-dopa = CO2 + dopamine 5-hydroxy-L-tryptophan + H(+) = CO2 + serotonin Homodimer. Hypoderm isoform is expressed only in hypodermal epithelium and the CNS isoform only in central nervous system. Hypoderm isoform has high expression levels in hypoderm during late embryogenesis, late larval development, pupariation and adult eclosion. CNS isoform has constant expression level in CNS throughout the life cycle. By ecdysone. In larval epidermis, expression is rapidly induced. In adult epidermis expression responds to a pulse of hormone and there is a time lag between initial exposure and appearance of DDC. Three common molecular polymorphisms (2 in the promoter region and Phe-12) account for 15.5% of the genetic contribution to variance in life span, the polymorphisms are maintained by balancing selection. Belongs to the group II decarboxylase family.