Document Detail


Possible mechanisms of the efflux of glutamate from kidney mitochondria generated by the activity of mitochondrial glutaminase.
MedLine Citation:
PMID:  1174515     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The transport of glutamate across the inner membrane of kidney mitochondria and the influx of glutamine into the mitochondria was studied using an oxygen electrode, the swelling technique and by continous recording of the activity of the mitochondrial glutaminase by an NH4+-sensitive electrode. It is well known that the enzyme is activated by inorganic phosphate and strongly inhibited by glutamate. 1. Avenaciolide, Bromocresal purple and Bromothymol blue inhibited the respiration of the mitochondria almost completely in the presence of glutamate as substrate but not in the presence of glutamine. Production of aspartate during the oxidation of glutamine was not significantly inhibited by avenaciolide but it was markedly suppressed by Bomocresol purple and Bromothymol blue. 2. Swelling of kidney mitochondria in an isosmotic solution of glutamine and ammonium phosphate was not inhibted by avenaciolide or Bromocresol purple indicating that these substances do not inhibit the penetration of the mitochondrial membrane by glutamine or phosphate. 3. The activity of the mitochondrial glutaminase was strongly inhibited by avenaciolide or Bromocresol purple in the presence of inhibitos of respiration or an uncoupler but not in ther absence. Experimental data suggest that this was caused by the inhibition of glutamate efflux. The addition of a detergent removed this inhibition. On the basis of these observations it was concluded that two mechanisms exist which enable glutamate to leave the inner space of kidney mitochondria: (a) an electrogenic efflux coupled to the respiration-driven proton translocation and the presence of a membrane potential (positive outside) and (b) an electroneutral glutamate-hydroxyl antiporter which is inhibted by avenaciolide and which operates in both directions. Our observations do not support the existence of the electrogenic glutamine-glutamate antiporter or glutamate-aspartate exchange in the mitochondria studied.
Authors:
Z Kovacević
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  396     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1975 Sep 
Date Detail:
Created Date:  1975-12-28     Completed Date:  1975-12-28     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  325-34     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Bromcresol Purple / pharmacology
Bromthymol Blue / pharmacology
Glutamates / metabolism*
Glutaminase* / antagonists & inhibitors
Kidney / drug effects,  enzymology,  metabolism*,  ultrastructure
Lactones / pharmacology
Mitochondria / drug effects,  enzymology,  metabolism*
Mitochondrial Swelling / drug effects
Oxygen Consumption / drug effects
Rats
Swine
Chemical
Reg. No./Substance:
0/Glutamates; 0/Lactones; 115-40-2/Bromcresol Purple; 76-59-5/Bromthymol Blue; EC 3.5.1.2/Glutaminase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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