In the nervous system, could hydrolyze ATP and other nucleotides to regulate purinergic neurotransmission. Hydrolyzes ADP only to a marginal extent. Expressed in brain, heart, vas deferens, kidney, skeletal muscle, thymus, lung and spleen. Weak expression in liver. By FSH in Sertoli cells but not in peritubular cells; by cAMP in both type of cells. Belongs to the GDA1/CD39 NTPase family.