Development of NAD(P)H: and NADH:Nitrate Reductase Activities in Soybean Cotyledons 1
AUTOR(ES)
Orihuel-Iranzo, Benito
RESUMO
The cotyledons of soybean begin to develop photosynthetic capacity shortly after emergence. The cotyledons develop nitrate reductase (NR) activity in parallel with an increase in chlorophyll and a decrease in protein. In crude extracts of 5- to 8-day-old cotyledons, NR activity is greatest with NADH as electron donor. In extracts of older cotyledons, NR activity is greatest with NADPH. Blue-Sepharose was used to purify and separate the NR activities into two fractions. When the blue-Sepharose was eluted with NADPH, NR activity was obtained which was most active with NADPH as electron donor. Assays of the NADPH-eluted NR with different concentrations of nitrate revealed that the highest activity was obtained in 80 millimolar KNO3. Thus, this fraction has properties similar to the low nitrate affinity NAD(P)H:NR of soybean leaves. When 5- to 8-day-old cotyledons were extracted and purified, further elution of the blue-Sepharose with KNO3, subsequent to the NADPH elution, yielded an NR fraction most active with NADH. Assays of this fraction with different nitrate concentrations revealed that this NR had a higher nitrate affinity and was similar to the NADH:NR of soybean leaves. The KNO3-eluted NR fraction which was purified from the extracts of 9- to 14-day-old cotyledons, was most active with NADPH. The analysis of these fractions prepared from the extracts of older cotyledons indicated that residual NAD(P)H:NR contaminated the NADH:NR. Despite this complication, the pattern of development of the purified NR fractions was consistent with the changes observed in the crude extract NR activities. It was concluded that NADH:NR was most active in young cotyledons and that as the cotyledons aged the NAD(P)H:NR became more active.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=440389Documentos Relacionados
- Purification and Characterization of NAD(P)H:Nitrate Reductase and NADH:Nitrate Reductase from Corn Roots 1
- NADH Nitrate Reductase and NAD(P)H Nitrate Reductase in Genetic Variants and Regenerating Callus of Maize
- Purification of NADH-Nitrate Reductase by Affinity Chromatography 1
- Expression of NADH-Specific and NAD(P)H-Bispecific Nitrate Reductase Genes in Response to Nitrate in Barley.
- Partial Purification of the NADH-Nitrate Reductase Complex from Chlorella pyrenoidosa1