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The distribution of glutamine synthetase in subcellular fractions of rat brain

Authors
Journal
Brain Research
0006-8993
Publisher
Elsevier
Publication Date
Volume
197
Issue
2
Identifiers
DOI: 10.1016/0006-8993(80)91131-2
Keywords
  • Rat Brain
  • Glutamine Synthetase Distribution
  • Glutamate Compartmentation
Disciplines
  • Biology

Abstract

Abstract The subcellular localization of glutamine synthetase, an enzyme fundamental to the compartmentation of glutamate hypothesis, was investigated using brain tissue of adult rats. The distribution of this enzyme in relation to the distribution of glucose-6-phosphatase, glutamate dehydrogenase and acetycholine esterase was studied using a fractionation scheme which had been previously extensively characterized in terms of intramitochondrial enzyme complements. Glutamine synthetase was found to be predominantly localized at the nerve terminal and a number of results suggested a possible association with the synaptic membrane. The observations are discussed in relation to the compartmentation of glutamate metabolism. Acetate and ammonia are precursors of the ‘small’ pool of glutamate from which most of the synthesis of glutamine occurs. Since one population of synaptic mitochondria has previously been shown to be enriched in glutamate dehydrogenase and acetyl CoA synthetase and in view of the current observations that synaptosomes are probably in association with a large proportion of brain glutamine synthetase, it is tentatively suggested that the synaptic complex represents at least in part the site of the ‘small’ glutamate pool.

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