Catalyzes the hydrolysis of nucleoside triphosphates and diphosphates in a calcium- or magnesium-dependent manner, with a preference for pyrimidines. Preferentially hydrolyzes UTP and TTP. AMP, ADP, ATP and UMP are not substrates (PubMed:10858452, PubMed:9556635). Preferentially activated by Ca(2+) over Mg(2+) (PubMed:10858452). Has a broad substrate specificity with the ability of cleaving all nucleotide di- and triphosphates with the exception of adenosine di- and triphosphate (ADP and ATP). Preferentially hydrolyzes CTP, UDP, CDP, GTP and GDP. Can use either Ca(2+) or Mg(2+) equally. a ribonucleoside 5'-diphosphate + H2O = a ribonucleoside 5'-phosphate + H(+) + phosphate a ribonucleoside 5'-triphosphate + H2O = a ribonucleoside 5'-diphosphate + H(+) + phosphate H2O + UDP = H(+) + phosphate + UMP H2O + UTP = H(+) + phosphate + UDP CTP + H2O = CDP + H(+) + phosphate GDP + H2O = GMP + H(+) + phosphate GTP + H2O = GDP + H(+) + phosphate H2O + TTP = H(+) + phosphate + TDP Ubiquitous. Highest expression in testis and lowest in bladder. Belongs to the GDA1/CD39 NTPase family.