| Registro completo |
| Provedor de dados: |
Braz. J. Plant Physiol.
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| País: |
Brazil
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| Título: |
Activation of nitrate reductase of cashew leaf by exogenous nitrite
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| Autores: |
Viégas,Ricardo Almeida
Silveira,Joaquim Albenísio Gomes
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| Data: |
2002-01-01
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| Ano: |
2002
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| Palavras-chave: |
Anacardium occidentale
Enzymes
NADH
Nitrate metabolism
Nitrate reductase
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| Resumo: |
Nitrate reductase (NR) plays a central role in plant primary metabolism and exhibits complex regulation mechanisms for its catalytic activity. There is controversy in the literature concerning the possible direct effect of NO2- on the stimulation and/or activation of NR activity. The influence of NO2- was studied on the NR activity in the leaves of 30-day-old cashew (Anacardium occidentale L.) seedlings. Addition of NO2- to the reaction mixture containing leaf enzymatic extract resulted in a remarkable increase in NR activity. A trace amount (5 mumol.L-1) of NO2- was required to achieve full NR activity. The in vitro NR-activity showed a steady time-dependent increase when incubated in the presence of only NO3- + NO2-. In contrast, in vitro NR activity was practically absent in a NO2- -free reaction medium, even in the presence of a saturating NO3- concentration. No oxidation of NO2- to NO3- was detected during the experiment. Although NO2- clearly activated the in vitro NR activity, it had no effect on the in vivo leaf-NR activity determined under absence of oxygen. NADH at concentrations greater than 0.5 mmol.L-1 decreased the rates of in vitro NR activity. These results indicated, at least partially, a strong cashew leaf NO2- dependency of NR activation and/or activity. Finally, based on these results, it is suggested that this singular NR activity model induced by exogenous NO2- in cashew leaf extracts is caused by changes in the NR activation state by NO2- itself.
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| Tipo: |
Info:eu-repo/semantics/article
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| Idioma: |
Inglês
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| Identificador: |
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1677-04202002000100005
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| Editor: |
Brazilian Journal of Plant Physiology
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| Relação: |
10.1590/S1677-04202002000100005
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| Formato: |
text/html
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| Fonte: |
Brazilian Journal of Plant Physiology v.14 n.1 2002
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| Direitos: |
info:eu-repo/semantics/openAccess
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