Histidine phosphatase domain found in histidine acid phosphatases and phytases; contains a His residue which is phosphorylated during the reaction.
Catalytic domain of HAP (histidine acid phosphatases) and phytases (myo-inositol hexakisphosphate phosphohydrolases). The conserved catalytic core of this domain contains a His residue which is phosphorylated in the reaction. Functions in this subgroup include roles in metabolism, signaling, or regulation, for example Escherichia coli glucose-1-phosphatase functions to scavenge glucose from glucose-1-phosphate and the signaling molecules inositol 1,3,4,5,6-pentakisphosphate (InsP5) and inositol hexakisphosphate (InsP6) are in vivo substrates for eukaryotic multiple inositol polyphosphate phosphatase 1 (Minpp1). Phytases scavenge phosphate from extracellular sources and are added to animal feed while prostatic acid phosphatase (PAP) has been used for many years as a serum marker for prostate cancer. Recently PAP has been shown in mouse models to suppress pain by functioning as an ecto-5prime-nucleotidase. In vivo it dephosphorylates extracellular adenosine monophosphate (AMP) generating adenosine,and leading to the activation of A1-adenosine receptors in dorsal spinal cord.
Comment:The catalytic core includes a His group which is phosphorylated during phosphoryl transfer as well as two key Arg residues and an additional His residue which are hydrogen bonded to the phospho group before, during, and after transfer.