The haloalkanoate dehalogenase (HAD) superfamily is one of the largest families of structurally homologous enzymes found ubiquitously in biological systems. Despite the name dehalogenase, the majority of members of the HAD superfamily possess phosphohydrolase activities as in ATPases and phosphatases. They share four conserved sequences that make up the α/β core-domain active site. In addition, each member possesses a unique cap domain that is responsible for substrate specificity.  The insertion location of the cap-domain sequence with respect to the four conserved sequences of the core domain further classifies these members into three different types. Upon substrate binding to the core-domain active site, the cap domain of type I and type II HAD enzymes changes conformation to close the active site to solvent. Members of type III HAD enzymes lack the cap domain and yet appear to recognize specific substrates. The “capless” Bordetella bronchiseptica CAE protein with 179 amino acids and molecular weight of 20 kDa is a hypothetical protein classified as one of the type III HAD members.  Our study aims at solving the X-ray crystal structure of this protein and other enzymes of this subclass in order to address the question of how substrate specificity is achieved in these “capless” family members. Genetic contextual information is consistent with assignment of the protein as D-glycero-D-manno-heptose 1,7-bisphosphatase, although substrate screening is consistent with a hexose phosphatase functionality.