Exhibits phosphohistidine phosphatase activity. May have a significant involvement in neuronal signaling. H2O + N(pros)-phospho-L-histidyl-[protein] = L-histidyl-[protein] + phosphate H2O + N(tele)-phospho-L-histidyl-[protein] = L-histidyl-[protein] + phosphate Monomer. Belongs to the janus family.