ENTPD8 is the canalicular ectonucleoside NTPDase responsible for the main hepatic NTPDase activity. Ectonucleoside NTPDases catalyze the hydrolyzis of gamma- and beta-phosphate residues of nucleotides, playing a central role in concentration of extracellular nucleotides. It has activity toward ATP, ADP, UTP and UDP, but not toward AMP.