Degradation of inorganic polyphosphates (polyP). Releases orthophosphate processively from the ends of the polyP chain. Prefers long-chain length polyphosphates as substrates. [phosphate](n) + H2O = [phosphate](n-1) + H(+) + phosphate Exopolyphosphatase activity is inhibited by ppGpp alarmones produced during the bacterial stringent response. Homodimer. PPX2 deficiency leads to increased polyP levels, early bacterial growth arrest and reduced susceptibility to the first-line drug isoniazid, as well as increased bacterial survival during exposure to stress conditions and within macrophages. Mutant shows increased thickness of the cell wall and reduced drug permeability. Belongs to the GppA/Ppx family.