title: Nitric oxide inhibits nitrate reductase activity in wheat leaves.
abstract: Nitrate reductase (NR), a committed enzyme in nitrate assimilation, is involved in the generation of nitric oxide (NO) in plants. In wheat leaf segments exposed to sodium nitroprusside (SNP) or S-nitrosoglutathione (GSNO), NR activity was significantly reduced to different degrees between 3 and 21 h, whereas its activity was partially recovered when the NO scavenger cPTIO was used. At 21 h, NR activity decreased from 38% with 10 μM SNP to 91% with 500 μM SNP, respect to the C values. S-nitrosoglutathione reduced NR activity between 18% and 26% only at 3 h. When added directly to the incubation solution, NR activity was quickly and strongly inhibited more than 90% by 10 or 50 μM SNP, whereas 10 μM GSNO reduced the enzyme activity an average of 50%, at 30 min of incubation. l-NAME and d-arginine (nitric oxide synthase (NOS) inhibitors) increased NR activity by 14% and 52% respectively, at 21 h of exposure, leading us to suppose that endogenous NOS-dependent NO formation could also be modulating NR activity. NR protein expression was not affected by 10 or 100 μM SNP at 3 or 21 h of incubation, whereas nitration of tyrosines was not detected in the NR protein. Nitrates, which content increased along the time in the tissues, could be exerting a role in this regulation.
authors.affiliation: Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina. eliprosales@gmail.com
authors.forename: Eliana Paola
authors.initials: EP
authors.lastname: Rosales
authors.forename: María Florencia
authors.initials: MF
authors.lastname: Iannone
authors.forename: María Daniela
authors.initials: MD
authors.lastname: Groppa
authors.forename: María Patricia
authors.initials: MP
authors.lastname: Benavides
mesh_terms: D015153:Blotting, Western; D004789:Enzyme Activation / Q000187:drug effects; D047468:Immunoprecipitation; D050901:Nitrate Reductase / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D009599:Nitroprusside / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D026422:S-Nitrosoglutathione / Q000494:pharmacology; D014908:Triticum / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism
chemical_list: D009566:Nitrates; D009599:Nitroprusside; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D050901:Nitrate Reductase