CD203c, a transmembrane protein and a member of the ectoenzyme family, is involved in the hydrolysis of extracellular oligonucleotides, nucleoside phosphates, and NAD (possesses ATPase and ATP pyrophosphatase activity). The molecular weight of CD203c was observed to be 130 and 150 kD under reducing conditions and 270 kD under non-reducing conditions. CD203c is expressed on basophils and mast cells, and is highly expressed on activated basophils. Secretory glands in endometrium and glioma cells are also positive. CD203c is a multifunctional ectoenzyme involved in the clearance of extracellular nucleotides whose substrates include nucleoside triphosphates, nucleoside diphosphates, cAMP, and NAD.