Catalyzes the decarboxylation of L-3,4-dihydroxyphenylalanine (DOPA) to dopamine and L-5-hydroxytryptophan to serotonin. H(+) + L-dopa = CO2 + dopamine 5-hydroxy-L-tryptophan + H(+) = CO2 + serotonin Catecholamine biosynthesis; dopamine biosynthesis; dopamine from L-tyrosine: step 2/2. Homodimer. Belongs to the group II decarboxylase family.