Data/hora: 03/06/2024 06:41:23

Provedor de dados: | 61
País: | Brazil
Título: | Activation of nitrate reductase of cashew leaf by exogenous nitrite
Autores: | Viégas,Ricardo Almeida; Silveira,Joaquim Albenísio Gomes.
Data: | 2002-01-01
Ano: | 2002
Palavras-chave: | Anacardium occidentale; Enzymes; NADH; Nitrate metabolism; Nitrate reductase.
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.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1677-04202002000100005
Editor: | Brazilian Journal of Plant Physiology
Relação: | 10.1590/S1677-04202002000100005
Formato: | text/html
Fonte: | Brazilian Journal of Plant Physiology  v.14 n.1 2002
Fonte: | info:eu-repo/semantics/openAccess