Marginally higher substrate specificity for L-DOPA over L-tyrosine. H(+) + L-tyrosine = CO2 + tyramine H(+) + L-dopa = CO2 + dopamine 5-hydroxy-L-tryptophan + H(+) = CO2 + serotonin Homodimer. Predominantly expressed in the roots. Belongs to the group II decarboxylase family.