title: Enzymatic and molecular characterization of Arabidopsis ppGpp pyrophosphohydrolase, AtNUDX26.
abstract: Not only in bacteria but also in plant cells, guanosine-3',5'-tetraphosphate (ppGpp) is an important signaling molecule, that affects various cellular processes. In this study, we identified nucleoside diphosphates linked to some moiety X (Nudix) hydrolases, AtNUDX11, 15, 25, and 26, having ppGpp pyrophosphohydrolase activity from Arabidopsis plants. Among these, AtNUDX26 localized in chloroplasts had the highest Vmax and kcat values, leading to high catalytic efficiency, kcat/Km. The activity of AtNUDX26 required Mg2+ or Mn2+ ions as cofactor and was optimal at pH 9.0 and 50 °C. The expression of AtNUDX26 and of ppGpp metabolism-associated genes was regulated by various types of stress, suggesting that AtNUDX26 regulates cellular ppGpp levels in response to stress and impacts gene expression in chloroplasts. This is the first report on the molecular properties of ppGpp pyrophosphohydrolases in plants.
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, Nara, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ito
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kato
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tamoi
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D002736:Chloroplasts / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006159:Guanosine Tetraphosphate / Q000378:metabolism; D042541:Intracellular Space / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D021381:Protein Transport; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics; D016963:Thermus thermophilus / Q000201:enzymology
chemical_list: D006159:Guanosine Tetraphosphate; C027627:guanosine-3',5'-bis(diphosphate) 3'-pyrophosphatase; D011755:Pyrophosphatases