In the nervous system, could hydrolyze ATP and other nucleotides to regulate purinergic neurotransmission. Hydrolyzes ADP only to a marginal extent. The order of activity with different substrates is ATP > GTP > CTP = ITP > UTP >> ADP = UDP. Brain, placenta, skeletal muscle, kidney, pancreas, heart, ovary, testis, colon, small intestine, prostate and pancreas. No expression in adult thymus, spleen, lung, liver and peripheral blood leukocytes. Catalytically inactive. Catalytically inactive. Belongs to the GDA1/CD39 NTPase family.