Cyanuric acid hydrolases (AtzD) and barbiturases are homologous and found almost exclusively in bacteria. Bioinformatic analysis has revealed a lack of bound metals in this proteins suggesting they do not belong, as it was previously thought, to the amidohydrolase superfamily PMID:22730121. AtzD is involved in cyanuric acid hydrolisis, process that releases carboxybiuret, which spontaneously decarboxylates to biuret, whilst barbituases cleave a single amide bond in the six-membered ring of barbiturate to yield ureidomalonic acid PMID:22730121.

Their structure is comprised of three 'repeating units' (RUs) that share the same structure as one another; they have been designated RU A (residues 3-104), B (residues 113-250) and C (residues 256-364), which, as shown in the PDB, correspond to superfamilies 3.30.1330.170, 3.30.1330.180 and 3.30.1330.160 respectively. Each RU is comprised of a four strand antiparallel beta-sheet and two helices PMID:23651355.