Phosphatase that hydrolyzes non-canonical purine nucleotides such as XTP and ITP to their respective diphosphate derivatives. Probably excludes non-canonical purines from DNA/RNA precursor pool, thus preventing their incorporation into DNA/RNA and avoiding chromosomal lesions. H2O + XTP = H(+) + phosphate + XDP H2O + ITP = H(+) + IDP + phosphate Binds 1 divalent metal cation per subunit; can use either Mg(2+) or Mn(2+). Homodimer. Belongs to the YjjX NTPase family.