Catalyzes the decarboxylation of L-tyrosine to tyramine, which is converted to norbelladine, a precursor to all Amaryllidaceae alkaloids such as galanthamine, lycorine and haemanthamine, and including haemanthamine- and crinamine-type alkaloids, promising anticancer agents. H(+) + L-tyrosine = CO2 + tyramine Alkaloid biosynthesis. Mostly expressed in bulbs, and, to a lower extent, in stems, roots, leaves and flowers. Belongs to the group II decarboxylase family.