futalosine nucleosidase which catalyzes the hydrolysis of futalosine to dehypoxanthinylfutalosine and a hypoxanthine base; similar to Thermus thermophiles MqnB
Futalosine nucleosidase (MqnB, EC 3.2.2.26, also known as futalosine hydrolase) functions in an alternative menaquinone biosynthetic pathway (the futalosine pathway) which operates in some bacteria, including Streptomyces coelicolor and Thermus thermophiles. This domain model belongs to the PNP_UDP_1 superfamily which includes members which accept a range of purine nucleosides as well as the pyrimidine nucleoside uridine. PNP_UDP_1 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). Superfamily members have different physiologically relevant quaternary structures: hexameric such as the trimer-of-dimers arrangement of Shewanella oneidensis MR-1 UP, homotrimeric such as human PNP and Escherichia coli PNPII (XapA), homohexomeric (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 PNP_UDP_2 (nucleoside phosphorylase-II family) is a different structural family.
Jiyao W et al.(2023). "The conserved domain database in 2023.",