Orn/DAP/Arg decarboxylase 2, N-terminal These enzymes are collectively known as group IV decarboxylases [<cite idref="PUB00001452"/>].Pyridoxal-dependent decarboxylases acting on ornithine, lysine, arginine andrelated substrates can be classified into two different families on the basisof sequence similarities [<cite idref="PUB00003632"/>, <cite idref="PUB00001452"/>].Members of this family while most probably evolutionary related, do not shareextensive regions of sequence similarities. The proteins contain a conserved lysineresidue which is known, in mouse ODC [<cite idref="PUB00002726"/>], to be the site of attachment of thepyridoxal-phosphate group. The proteins also contain a stretch of threeconsecutive glycine residues and has been proposed to be part of a substrate-binding region [<cite idref="PUB00002116"/>].