uncharacterized subfamily of the nucleoside phosphorylase-I family
This subfamily is composed of uncharacterized members including Streptococcus pneumoniae hypothetical protein spr0068. The nucleoside phosphorylase-I (NP-I) family members accept a range of purine nucleosides as well as the pyrimidine nucleoside uridine. The NP-1 family includes phosphorolytic nucleosidases such as purine nucleoside phosphorylase (PNP, EC. 2.4.2.1), uridine phosphorylase (UP, EC 2.4.2.3), and 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAP, EC 2.4.2.28), and hydrolytic nucleosidases such as AMP nucleosidase (AMN, EC 3.2.2.4) and 5'-methylthioadenosine/S-adenosylhomocysteine (MTA/SAH) nucleosidase (MTAN, EC 3.2.2.16). Members of the NP-I family display different physiologically relevant quaternary structures: hexameric (trimer-of-dimers arrangement of Shewanella oneidensis MR-1 UP); homotrimeric (human PNP and Escherichia coli PNPII or XapA); hexameric (with some evidence for co-existence of a trimeric form) such as E. coli PNPI (DeoD); or homodimeric such as human and Trypanosoma brucei UP. The NP-I family is distinct from nucleoside phosphorylase-II, which belongs to a different structural family.
Comment:based on nucleoside phosphorylase-I family members with structures; reactions involved includes phosphorolysis and hydrolysis; includes hexameric, trimeric, and dimeric quaternary structures
Comment:for many, the neighboring subunit of a dimer contributes residue(s) to the protein-ligand interaction
Jiyao W et al.(2023). "The conserved domain database in 2023.",