<p>This small family comprises proteins containing one copy of the metallophosphoesterase domain. They possess motifs characteristic of a variety of enzymatically active phosphoesterases [<cite idref="PUB00014394"/>], including acid and alkaline phosphatases, phosphoprotein phosphatases, 5'-nucleotidase, bis(5'-nucleosyl)-tetraphosphatase (symmetrical), sphingomyelin phosphodiesterase, 2',3'-cylic-nucleotide 2'-phosphodiesterase and the 3',5'-nucleotide phosphodiesterase CpdA.</p>