InterPro domain: IPR002433

These enzymes are collectively known as group IV decarboxylases [ 1 ].Pyridoxal-dependent decarboxylases acting on ornithine, lysine, arginine andrelated substrates can be classified into two different families on the basisof sequence similarities [ 2 , 3 ].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 [ 3 ], 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 [ 4 ].

The ornithine decarboxylases catalyse the transformation of ornithine into putrescine. Phylogenetic analysis of the mRNAs from several mammalian species suggests that ODC is encoded by orthologous genes in the different species. Analysis of divergence patterns in a number of subregions showed that the domains have evolved in a noncoordinate fashion. Evolution of each subregion has been episodic, with periods of both rapid and slow divergence, possibly indicating the existence of selection pressures that were exerted in a time- and domain-specific manner during mammalian speciation. The active form of mammalian ODC is a homodimer of 53kDa subunits (the monomer retains no enzymatic activity). In vitro hybridisation and cross- linkage analysis have suggested that the active site of ODC is formed at the interface of the two monomers via the interaction of the cysteine-360- containing region of one subunit with the lysine-69-containing region of the other [ 5 ].

This family also includes antizyme inhibitors (AZINs), which are ODC-homologous proteins lacking catalytic activity. They bind and inhibit the ODC antizyme [ 5 ].

1. Multiple evolutionary origin of pyridoxal-5'-phosphate-dependent amino acid decarboxylases. Eur. J. Biochem. 221, 997-1002
2. Pseudomonas aeruginosa diaminopimelate decarboxylase: evolutionary relationship with other amino acid decarboxylases. Mol. Biol. Evol. 5, 549-59
3. Mechanism of the irreversible inactivation of mouse ornithine decarboxylase by alpha-difluoromethylornithine. Characterization of sequences at the inhibitor and coenzyme binding sites. J. Biol. Chem. 267, 150-8
4. Nucleotide sequence and analysis of the speA gene encoding biosynthetic arginine decarboxylase in Escherichia coli. J. Bacteriol. 172, 4631-40
5. Cloning of antizyme inhibitor, a highly homologous protein to ornithine decarboxylase. J. Biol. Chem. 271, 3340-2