<p>This group of proteins is a part of the haloacid dehalogenase (HAD) superfamily of aspartate-nucleophile hydrolases. The Class III subfamilies are characterised by the lack of any domains located either between the first and second conserved catalytic motifs (as in the Class I subfamilies) or between the second and third conserved catalytic motifs (as in the Class II subfamilies) of the superfamily domain [<cite idref="PUB00003337"/>, <cite idref="PUB00009589"/>]. The IIIA subfamily contains five major clades: histidinol-phosphatase [<cite idref="PUB00009674"/>], histidinol-phosphatase-related protein, DNA 3-phosphatase and sequences related to YqeG and YrbI.</p>