<p>A number of pyridoxal-dependent decarboxylases share regions of sequence similarity, particularly in the vicinity of a conserved lysine residue, which provides the attachment site for the pyridoxal-phosphate (PLP) group [<cite idref="PUB00001452"/>, <cite idref="PUB00003414"/>]. Among these enzymes are aromatic-L-amino-acid decarboxylase (L-dopa decarboxylase or tryptophan decarboxylase), which catalyses the decarboxylation of tryptophan to tryptamine [<cite idref="PUB00002358"/>]; tyrosine decarboxylase, whichconverts tyrosine into tyramine; and histidine decarboxylase, which catalyses the decarboxylation of histidine to histamine [<cite idref="PUB00004715"/>]. These enzymes belong to the group II decarboxylases [<cite idref="PUB00001452"/>, <cite idref="PUB00002358"/>].</p> Aromatic-L-amino-acid decarboxylase