Data/hora: 20/05/2024 05:36:15

Provedor de dados: 	Brazilian Journal of Plant Physiology	
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