Hydrolyzes UDP and to a lesser extent GDP. By preventing the accumulation of NDP, may promote the reglucosylation of incompletely folded glycoproteins in the endoplasmic reticulum following the unfolded protein response. a ribonucleoside 5'-diphosphate + H2O = a ribonucleoside 5'-phosphate + H(+) + phosphate By ER stress. RNAi-mediated knockdown causes a 50% reduction of progeny numbers and a slower growth. RNAi-mediated knockdown at the L4 larval stage results in a reduced lifespan and in the lysosomal accumulation of lipofuscin in the intestine with age. Motility is decreased and muscle sarcomeres are often patched or wrinkled. Moderate decrease in pharyngeal pumping associated with an abnormal pharynx morphology characterized by irregular and discontinued cell junction protein ajm-1 localization at the beginning and at the end of the procorpus and in the isthmus and a loss of one of the three loops forming the lumen. In addition, causes the up-regulation of ER stress marker hsp-4 which is prevented in an ire-1 mutant background. UDPase and to a lesser extent GDPase activities are reduced. Belongs to the apyrase family.