In the nervous system, could hydrolyze ATP and other nucleotides to regulate purinergic neurotransmission. Could also be implicated in the prevention of platelet aggregation by hydrolyzing platelet-activating ADP to AMP. Hydrolyzes ATP and ADP equally well. a ribonucleoside 5'-triphosphate + 2 H2O = a ribonucleoside 5'-phosphate + 2 H(+) + 2 phosphate Optimum pH is 7.0-7.5 with ATP as substrate, and 7.5-8.0 with ADP as substrate. Homodimer; disulfide-linked. Expressed primarily on activated lymphoid cells. Also expressed in endothelial tissues. Isoform 1 and isoform 3 are present in both placenta and umbilical vein, whereas isoform 2 is present in placenta only. The N-terminus is blocked. Palmitoylated in the N-terminal part. The disease is caused by variants affecting the gene represented in this entry. Belongs to the GDA1/CD39 NTPase family.