Document Detail


Oxidative metabolism of 4-aminobutyrate by rat brain mitochondria: inhibition by branched-chain fatty acid.
MedLine Citation:
PMID:  7452235     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The oxidation of 4-aminobutyric acid (GABA) by nonsynaptosomal mitochondria isolated from rat forebrain and the inhibition of this metabolism by the branched-chain fatty acids 2-methyl-2-ethyl caproate (MEC) and 2.2-dimethyl valerate (DMV) were studied. The rate of GABA oxidation, as measured by O2 uptake, was determined in medium containing either 5 or 100 mM-[K+]. The apparent Km for GABA was 1.16 +/- 0.19 mM and the Vmax in state 3 was 23.8 +/- 5.5 ng-atoms O2 x min-1 x mg protein-1 in 5 m M-[K+]. In a medium with 100 mM-[K+] the apparent Km was 1.11 +/- 0.17 mM and Vmax was 47.4 +/- 5.7 ng-atoms O2 x min-1 x mg protein-1. The Ki for MEC was determined to be 0.58 +/- 0.24 or 0.32 +/- 0.08 mM, in 5 or 100 mM-[K+], respectively. For DMV, the Ki was 0.28 +/- 0.05 or 0.34 +/- 0.06 mM, in 5 or 100 mM-[K+] medium, respectively. The O2 uptake of the mitochondria in the presence of GABA was coupled to the formation of glutamate and aspartate; the ratio of oxygen uptake to the rate of amino acid formation was close to the theoretical value of 3. Neither the [K+] nor any of the above inhibitors had any effect on this ratio. The metabolism of exogenous succinic semialdehyde (SSA) by these same mitochondria was also examined. The Vmax for utilization of oxygen in the presence of SSA was much greater than that found with exogenously added GABA, indicating that the capacity for GABA oxidation by these mitochondria is not limited by SSA dehydrogenase. In addition, the branched-chain fatty acids did not inhibit the metabolism of exogenously added SSA. Thus, the inhibitors examined apparently act by competitively inhibiting the GABA transaminase system of the mitochondria.
Authors:
J Cunningham; D D Clarke; W J Nicklas
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of neurochemistry     Volume:  34     ISSN:  0022-3042     ISO Abbreviation:  J. Neurochem.     Publication Date:  1980 Jan 
Date Detail:
Created Date:  1981-03-17     Completed Date:  1981-03-17     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985190R     Medline TA:  J Neurochem     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  197-202     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Aspartic Acid / metabolism
Brain / drug effects,  metabolism*
Caproates / pharmacology*
Glutamates / metabolism
Hexanoic Acids / pharmacology*
Kinetics
Mitochondria / metabolism*
Oxidation-Reduction
Oxygen Consumption / drug effects
Pentanoic Acids / pharmacology*
Rats
Valerates / pharmacology*
gamma-Aminobutyric Acid / metabolism*
Grant Support
ID/Acronym/Agency:
MH 25505/MH/NIMH NIH HHS; NS 11631/NS/NINDS NIH HHS
Chemical
Reg. No./Substance:
0/Caproates; 0/Glutamates; 0/Hexanoic Acids; 0/Pentanoic Acids; 0/Valerates; 1185-29-1/2-methyl-2-ethylcaproic acid; 1185-39-3/2,2-dimethylvaleric acid; 56-12-2/gamma-Aminobutyric Acid; 56-84-8/Aspartic Acid

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


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