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5'-methylthioadenosine/S-adenosylhomocysteine nucleosidases This subfamily includes both bacterial and plant 5'-methylthioadenosine/S-adenosylhomocysteine (MTA/SAH) nucleosidases (MTANs): bacterial MTANs show comparable efficiency in hydrolyzing MTA and SAH, while plant enzymes are highly specific for MTA and are unable to metabolize SAH or show significantly reduced activity towards SAH. MTAN is involved in methionine and S-adenosyl-methionine recycling, polyamine biosynthesis, and bacterial quorum sensing. This subfamily belongs to the nucleoside phosphorylase-I (NP-I) family, whose 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 (PNPs, 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). The NP-I family is distinct from nucleoside phosphorylase-II, which belongs to a different structural family. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",