Document Detail

Energetics of Amino Acid Uptake by Vicia faba Leaf Tissues.
MedLine Citation:
PMID:  16662764     Owner:  NLM     Status:  PubMed-not-MEDLINE    
The uptake of [U-(14)C]threonine and of (alpha-(14)C]aminoisobutyrate (alpha-AIB) by Vicia faba leaf discs is strongly pH dependent (optimum: pH 4.0) and exhibits biphasic saturation kinetics. Kinetics of alpha-AIB uptake at different pH values indicate that acidic pH values decrease the K(m) of the carriers while the maximal velocity remains nearly unaffected. Similar results were obtained for both system 1 (from 0.5 to 5 millimolar) and system 2 (from 20 to 100 millimolar).After addition of amino acids to a medium containing leaf fragments, alkalinizations depending both on the amino acid added and on its concentration have been recorded.The effects of compounds which increase (fusicoccin) or decrease (uncouplers, ATPase inhibitors, high KCl concentrations) the protonmotive force were studied both on the acidification of the medium and on amino acid uptake by the tissues. There is a close relationship between the time required for the effect of these compounds on the acidification and that needed for inhibition of uptake.Studies with thiol inhibitors show that 0.1 millimolar N-ethylmaleimide preferentially inhibits uptake by the mesophyll whereas 0.1 millimolar parachloromercuribenzenesulfonate affects rather uptake by the veins.New evidence was found which added to the electrophysiological data already supporting the occurrence of proton amino acid symport in leaf tissues, particularly in the veins.
J P Despeghel; S Delrot
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  71     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1983 Jan 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-06-29     Revised Date:  2010-09-15    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1-6     Citation Subset:  -    
Station Biologique de Beau-Site, 25 Faubourg St-Cyprien, 86000 Poitiers, France.
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