<p>This is a group of authentic histidinol-phosphate phosphatases which are sometimes found as stand-alone entities and sometimes as fusions with imidazoleglycerol-phosphate dehydratase. Additionally, a family of proteins including YaeD from <taxon tax_id="562">Escherichia coli</taxon> and various other proteins are closely related but may not have the same substrate specificity. This protein is a member of the haloacid-dehalogenase (HAD) superfamily of aspartate-nucleophile hydrolases. This superfamily is distinguished by the presence of three motifs: an N-terminal motif containing the nucleophilic aspartate, a central motif containing a conserved serine or threonine, and a C-terminal motif containing a conserved lysine (or arginine) and conserved aspartates. More specifically, the region modelled here is a member of subfamily III of the HAD-superfamily by virtue of lacking a "capping" domain in either of the two common positions, between motifs 1 and 2, or between motifs 2 and 3.</p>