/sup 15/N-Ammonia assimilation, 2-oxoglutarate transport, and glutamate export in spinach chloroplasts in the presence of dicarboxylates in the light
The direct incorporation of /sup 15/NH/sub 4/Cl into amino acids in illuminated spinach (Spinacia oleracea L.) chloroplasts in the presence of 2-oxoglutarate plus malate was determined. The amido-N of glutamine was the most highly labeled N-atom during /sup 15/NH/sub 4/ assimilation in the presence of malate. In 4 minutes the /sup 15/N-label of the amido-N of glutamine was 37% enriched. In contrast, values obtained for both the N-atom of glutamate and the amino-N of glutamine were only about 20% while that of the N-atom of aspartate was only 3%. The addition of malate during the assimilation of /sup 15/NH/sub 4/Cl and Na/sup 15/NO/sub 2/ greatly increased the /sup 15/N-label into glutamine but did not qualitatively change the order of the incorporation of /sup 15/N-label into all the amino acids examined. This evidence indicates the direct involvement of the glutamine synthetase/glutamate synthase pathway for ammonia and nitrite assimilation in isolated chloroplasts. The addition of malate or succinate during ammonia assimilation also led to more than 3-fold increase in (/sup 14/C)2-oxoglutarate transport into the chloroplast as well as an increase in the export of (/sup 14/C)glutamate out of the chloroplast. Little (/sup 14/C)glutamine was detected in the medium of the chloroplast preparations. The stimulation of /sup 15/N-incorporation and (/sup 14/C)glutamate export by malate could be directly attributed to the increase in 2-oxoglutarate transport activity (via the 2-oxoglutarate translocator) observed in the presence of exogenous malate.
- Research Organization:
- Australian National Univ., Canberra City
- OSTI ID:
- 5562387
- Journal Information:
- Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 85:3; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AMIDES
AMINO ACIDS
AMMONIA
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHLOROPLASTS
DICARBOXYLIC ACIDS
ELECTROMAGNETIC RADIATION
FOOD
GLUTAMIC ACID
GLUTAMINE
GLUTARIC ACID
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXY ACIDS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MALIC ACID
MEMBRANE TRANSPORT
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLANTS
RADIATIONS
SPINACH
STABLE ISOTOPES
SYNTHESIS
TRACER TECHNIQUES
VEGETABLES
VISIBLE RADIATION