| Evidence for an operative glutamine translocator in chloroplasts from maritime pine (Pinus pinaster Ait.) cotyledons. | |
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MedLine Citation:
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PMID: 20701694 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In higher plants, ammonium is assimilated into amino acids through the glutamine synthetase (GS)/glutamate synthase (GOGAT) cycle. This metabolic cycle is distributed in different cellular compartments in conifer seedlings: glutamine synthesis occurs in the cytosol and glutamate synthesis within the chloroplast. A method for preparing intact chloroplasts of pine cotyledons is presented with the aim of identifying a glutamine-glutamate translocator. Glutamine-glutamate exchange has been studied using the double silicone layer system, suggesting the existence of a translocator that imports glutamine into the chloroplast and exports glutamate to the cytoplasm. The translocator identified is specific for glutamine and glutamate, and the kinetic constants for both substrates indicate that it is unsaturated at intracellular concentrations. Thus, the experimental evidence obtained supports the model of the GS/GOGAT cycle in developing pine seedlings that accounts for the stoichiometric balance of metabolites. As a result, the efficient assimilation of free ammonia produced by photorespiration, nitrate reduction, storage protein mobilisation, phenylpropanoid pathway or S-adenosylmethionine synthesis is guaranteed. |
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Authors:
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M G Claros; M L Aguilar; F M Cánovas |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Plant biology (Stuttgart, Germany) Volume: 12 ISSN: 1438-8677 ISO Abbreviation: Plant Biol (Stuttg) Publication Date: 2010 Sep |
Date Detail:
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Created Date: 2010-08-12 Completed Date: 2010-10-28 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101148926 Medline TA: Plant Biol (Stuttg) Country: England |
Other Details:
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Languages: eng Pagination: 717-23 Citation Subset: IM |
Affiliation:
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Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain. claros@uma.es |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Ammonia
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metabolism Cell Fractionation / methods Chloroplasts / enzymology* Cotyledon / enzymology Glutamate Synthase / metabolism* Glutamate-Ammonia Ligase / metabolism* Glutamic Acid / metabolism Glutamine / metabolism* Pinus / enzymology* Plant Proteins / metabolism |
| Chemical | |
Reg. No./Substance:
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0/Plant Proteins; 56-85-9/Glutamine; 56-86-0/Glutamic Acid; 7664-41-7/Ammonia; EC 1.4.1.13/Glutamate Synthase; EC 6.3.1.2/Glutamate-Ammonia Ligase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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