Involved in pyrimidine breakdown, especially in response to dark stress (PubMed:21599668, PubMed:30787180). In the presence of URH1, exhibits efficient inosine and xanthosine hydrolytic activities (PubMed:21599668, PubMed:30787180). Support inosine breakdown especially during the late phase of senescence (PubMed:21235647). H2O + uridine = D-ribose + uracil H2O + inosine = D-ribose + hypoxanthine H2O + xanthosine = D-ribose + xanthine kcat is 23.3 sec(-1) with xanthosine as substrate (when in complex with URH2) (PubMed:30787180). kcat is 55.3 sec(-1) with uridine as substrate (when in complex with URH2) (PubMed:30787180). kcat is 42.3 sec(-1) with inosine as substrate (when in complex with URH2) (PubMed:30787180). Component of the NSH heterocomplex made of URH1/NSH1 and URH2/NSH2 which exhibits strong xanthosine nucleosidase activity (PubMed:30787180). Interacts with URH1 (PubMed:30787180). Expressed in roots, seedlings and flowers. Accumulates during senescence. Normal seedling germination and plant growth and development in standard conditions (PubMed:21599668). No abnormal levels of nucleoside intermediates (PubMed:21599668). The roots of the double mutant urh1 urh2 accumulates strong levels of xanthosine (PubMed:21599668, PubMed:30787180). Belongs to the IUNH family.