Calcium-dependent nucleotidase with a preference for UDP. The order of activity with different substrates is UDP > GDP > UTP > GTP. Has very low activity towards ADP and even lower activity towards ATP. Does not hydrolyze AMP and GMP (PubMed:12234496, PubMed:15248776, PubMed:15006348, PubMed:16835225). Involved in proteoglycan synthesis (PubMed:22539336). a ribonucleoside 5'-diphosphate + H2O = a ribonucleoside 5'-phosphate + H(+) + phosphate Optimum pH is 6.8. Monomer (PubMed:12234496, PubMed:15006348). Homodimer; dimerization is Ca(2+)-dependent (PubMed:16835225). Homodimer; disulfide-linked (membrane form) (PubMed:16835225). Processed form: Secreted. Widely expressed. N-glycosylated. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Not inhibited by azide. Belongs to the apyrase family. Truncated N-terminus.