Catalyzes the hydrolysis of phytate (or myo-inositol hexakisphosphate, an indigestible organic form of phosphorus that is found in many plant tissues) to myo-inositol and inorganic phosphate (PubMed:8387749, Ref.8, PubMed:10696472, PubMed:11035187, PubMed:30712472). Dephosphorylates phytate in a stereospecific way by sequential removal of phosphate groups to produce myo-inositol 2-monophosphate (PubMed:11035187). Also shows phosphoanhydride phosphatase activity and hydrolyzes the distal phosphoryl residues of GTP, the 5'-beta-phosphoryl residue of the regulatory nucleotide ppGpp and tripolyphosphates (PubMed:6282821, PubMed:1429631, PubMed:8407904). Does not split most phosphomonoesters with the exception of the synthetic substrate p-nitrophenyl phosphate (pNPP), 2,3-bisphosphoglycerate and fructose 1,6-bisphosphate (PubMed:6282821, Ref.8, PubMed:1429631, PubMed:8387749, PubMed:8407904, PubMed:10696472). 1D-myo-inositol hexakisphosphate + H2O = 1D-myo-inositol 1,2,3,4,5-pentakisphosphate + phosphate 1D-myo-inositol 1,2,3,4,5-pentakisphosphate + H2O = 1D-myo-inositol 2,3,4,5-tetrakisphosphate + phosphate 1D-myo-inositol 2,3,4,5-tetrakisphosphate + H2O = 1D-myo-inositol 2,4,5-triphosphate + phosphate 1D-myo-inositol 2,4,5-triphosphate + H2O = 1D-myo-inositol 2,5-bisphosphate + phosphate 1D-myo-inositol 2,5-bisphosphate + H2O = 1D-myo-inositol 2-phosphate + phosphate GTP + H2O = GDP + H(+) + phosphate Contains three consecutive and one non-consecutive disulfide bonds and shows a strong dependence on DsbC for its full activity (PubMed:15642731). Competitively inhibited by tartaric acid and by sodium fluorid (PubMed:6282821, PubMed:8387749). Optimum pH is 4.5 for phytase activity (PubMed:8387749, PubMed:10696472). Optimum pH is 2.5 for acid phosphatase activity (PubMed:6282821). Optimum pH is 2.5-3.0 for acid phosphatase activity (PubMed:10696472). Optimum temperature is 55 degrees Celsius for phytase activity (PubMed:8387749). Optimum temperature is 60 degrees Celsius for phytase activity (PubMed:10696472). Monomer. Induced by phosphate starvation, anaerobiosis and entry into stationary phase (PubMed:6282821, PubMed:8387749, PubMed:8071219). Regulated by the HTH-type transcriptional regulator AppY (PubMed:8071219). Negatively controlled by the cAMP-cAMP receptor (CAP) complex (PubMed:6282821, PubMed:3038201). The properties of the phytase including the low pH optimum, protease resistance and high activity, demonstrate that the enzyme is a good candidate for industrial production as a feed enzyme and is therefore of potential commercial interest. Belongs to the histidine acid phosphatase family.