<p>This family is composed of ornithine decarboxylases (ODC), arginine decarboxylases (ADC) and lysinedecarboxylases (LDC), and belongs to the pyridoxal phosphate (PLP)-dependent aspartate aminotransferase domainsuperfamily (fold I) [<cite idref="PUB00001452"/>]. These enzymes catalyse the decarboxylation of ornithine,arginine, or lysine, respectively using PLP as a co-factor. ODC is active as a dimer and catalyses thedecarboxylation of tryptophan [<cite idref="PUB00014437"/>]. ADC catalyses the decarboxylation of arginine and LDCcatalyses the decarboxylation of lysine. The PLP combines with the alpha-amino acid to form a Schiff base, whichacts as the substrate in the decarboxylation (COOH group removal) reaction [<cite idref="PUB00014393"/>].</p> <p>Pyridoxal phosphate (PLP) dependent enzymes were previously classified into alpha,beta and gamma classes, based on the chemical characteristics (carbon atom involved) of the reaction theycatalysed. The availability of several structures allowed a comprehensive analysis of the evolutionaryclassification of PLP dependent enzymes, and it was found that the functional classification did not alwaysagree with the evolutionary history of these enzymes. Structure and sequence analysis has revealed that the PLPdependent enzymes can be classified into four major groups of different evolutionary origin: aspartateaminotransferase superfamily (fold type I), tryptophan synthase beta superfamily (fold type II), alanineracemase superfamily (fold type III), D-amino acid superfamily (fold type IV) and glycogen phophorylase family(fold type V) [<cite idref="PUB00006301"/>, <cite idref="PUB00006322"/>].</p> <p>For additional information please see[<cite idref="PUB00014378"/>, <cite idref="PUB00014382"/>].</p> Ornithine/lysine/arginine decarboxylase