title: MJ0917 in archaeon Methanococcus jannaschii is a novel NADP phosphatase/NAD kinase.
abstract: NAD kinase phosphorylates NAD(+) to form NADP(+). Conversely, NADP phosphatase, which has not yet been identified, dephosphorylates NADP(+) to produce NAD(+). Among the NAD kinase homologs, the primary structure of MJ0917 of hyperthermophilic archaeal Methanococcus jannaschii is unique. MJ0917 possesses an NAD kinase homologous region in its C-terminal half and an inositol-1-phosphatase homologous region in its N-terminal half. In this study, MJ0917 was biochemically shown to possess both NAD kinase and phosphatase activities toward NADP(+), NADPH, and fructose 1,6-bisphosphate, but not toward inositol 1-phosphate. With regard to the phosphatase activity, kinetic values indicated that NADP(+) is the preferred substrate and that MJ0917 would function as a novel NADP phosphatase/NAD kinase showing conflicting dual activities, viz. synthesis and degradation of an essential NADP(+). Furthermore, in vitro analysis of MJ0917 showed that, although MJ0917 could supply NADP(+), it prevented excess accumulation of NADP(+); thus, it has the ability to maintain a high NAD(+)/NADP(+) ratio, whereas 5'-AMP would decrease this ratio. The evolutionary process during which MJ0917 arose is also discussed.
authors.affiliation: Department of Basic and Applied Molecular Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kawai
authors.forename: Chikako
authors.initials: C
authors.lastname: Fukuda
authors.forename: Takako
authors.initials: T
authors.lastname: Mukai
authors.forename: Kousaku
authors.initials: K
authors.lastname: Murata
mesh_terms: D019843:Archaeal Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019143:Evolution, Molecular; D007700:Kinetics; D017017:Methanococcus / Q000201:enzymology* / Q000235:genetics; D009708:Nucleotidases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D019843:Archaeal Proteins; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; C045660:NADP phosphatase; D009708:Nucleotidases