May play an important role in providing precursors for alkaloid synthesis in the roots and germinating seedlings. H(+) + L-tyrosine = CO2 + tyramine H(+) + L-dopa = CO2 + dopamine 5-hydroxy-L-tryptophan + H(+) = CO2 + serotonin Homodimer. Roots. Belongs to the group II decarboxylase family.