Catalyzes the hydrolysis of phosphoanhydride bonds of nucleoside tri- and di-phosphates. Required for Golgi glycosylation and cell wall integrity. Involved in N-mannosylation of proteins in Golgi. a ribonucleoside 5'-triphosphate + 2 H2O = a ribonucleoside 5'-phosphate + 2 H(+) + 2 phosphate Divalent metal cations. Ca(2+), Mg(2+) or Mn(2+). Protein modification; protein glycosylation. Belongs to the GDA1/CD39 NTPase family.