Histidine phosphatase domain found in a functionally diverse set of proteins, mostly phosphatases; contains a His residue which is phosphorylated during the reactionCatalytic domain of a functionally diverse set of proteins, most of which are phosphatases. The conserved catalytic core of this domain contains a His residue which is phosphorylated in the reaction. This set of proteins includes cofactor-dependent and cofactor-independent phosphoglycerate mutases (dPGM, and BPGM respectively), fructose-2,6-bisphosphatase (F26BP)ase, Sts-1, SixA, histidine acid phosphatases, phytases, and related proteins. Functions include roles in metabolism, signaling, or regulation, for example F26BPase affects glycolysis and gluconeogenesis through controlling the concentration of F26BP; BPGM controls the concentration of 2,3-BPG (the main allosteric effector of hemoglobin in human blood cells); human Sts-1 is a T-cell regulator; Escherichia coli Six A participates in the ArcB-dependent His-to-Asp phosphorelay signaling system; phytases scavenge phosphate from extracellular sources. Deficiency and mutation in many of the human members result in disease, for example erythrocyte BPGM deficiency is a disease associated with a decrease in the concentration of 2,3-BPG. Clinical applications include the use of prostatic acid phosphatase (PAP) as a serum marker for prostate cancer. Agricultural applications include the addition of phytases to animal feed.