The Story of Glutamine Synthetase Regulation

Stadtman, Earl R.

doi:10.1074/jbc.r100055200

Cited by 151 publications

(144 citation statements)

References 49 publications

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“…Perhaps E . coli contains a thiophorase like the one studied in detail by Stadtman [43]. A third possibility would be the activation with butyryl-phosphate as an intermediate, a pathway occurring in Clostridium butyricum [44].…”

Section: Chain Length Specificity Of Enzyme Inductionmentioning

confidence: 99%

Fatty Acid Degradation in Escherichia coli

Overath¹,

Pauli²,

Schairer³

1969

European Journal of Biochemistry

313

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1. An enzymatic activity is described in oleate-grown cells of E. coli, which has the cofactor requirements of a long chain acid : CoA ligase (AMP). This enzyme is a t least partially membrane bound and activates saturated and mono-and polyunsaturated fatty acids. It is inactive with butyrate and hexanoate. The enzyme is induced by oleate under similar conditions, but a t different relative rates, as three other enzymes of fatty acid degradation (thiolase, crotonase, hydroxyacylCoA dehydrogenase) which are under coordinate control. 2.A mutant lacking acyl-CoA synthetase synthesizes the other three enzymes at the basal rate of the wild type in the presence or absence of oleate in the medium. This suggests that the fatty acyl-CoA derivatives rather than the fatty acids serve as inducers. The same mutant is unable to incorporate fatty acids into bacterial lipids. The acyl-CoA synthetase is therefore required for lipid synthesis from exogenous fatty acids in vivo.3. The isolation and properties of mutants unable to degrade oleate are described. A pleiotropic mutant lacking thiolase, crotonase and hydroxyacyl-CoA dehydrogenase still contains the inducible acyl-CoA synthetase. Mutants lacking thiolase and hydroxyacyl-CoA dehydrogenase have inducible wild type levels of the other enzymes.4. Mutants affecting the synthesis of thiolase, hydroxyacyl-CoA dehydrogenase or crotonase map between the loci metE and rha on the E . coli-chromosome and are probably closely linked. The mutant lacking acyl-CoA synthetase is not linked to the other mutants and maps near the his-locus.5. Only fatty acids with more than twelve carbon atoms serve as inducers or can be used as sole carbon source by the wild type. This specificity is therefore typical for the abolition of repression by the interaction with the fatty acids.6. Spontaneous mutants can be isolated which grow on decanoate. These are constitutive for the synthesis of all four enzymes investigated and can only grow on fatty acids with more than eight carbon atoms. Thus, after destruction of the repression mechanism the growth behavior is a reflection of the substrate specificity of the acyl-CoA synthetase.7. Starting with the constitutive mutants, spontaneous mutants have been isolated which can grow on butyrate. These fall into two classes: (a) One class grows on butyrate and poorly on long chain fatty acids. It makes all four enzymes constitutively but has twenty times more thiolase activity than the parent. This thiolase activity is not due to a gene linked to metE. (b) The other class can grow on butyrate and fatty acids with more than eight carbon atoms. It synthesizes the enzymes constitutively.8. The data suggest that the expression of the linked structural genes of crotonase, hydroxyacyl-CoA dehydrogenase and thiolase and the unlinked gene of the acyl-CoA synthetase form a regulon which is controlled by a common regulator gene.

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Section: Chain Length Specificity Of Enzyme Inductionmentioning

confidence: 99%

Fatty Acid Degradation in Escherichia coli

Overath¹,

Pauli²,

Schairer³

1969

European Journal of Biochemistry

313

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“…In nitrogen-excess conditions (high glutamine and low a-KG), GlnD acts as a uridylyl-removing enzyme to deuridylylate P II , which interacts with a different but overlapping set of receptor proteins to regulate them appropriately. In many bacteria the receptor proteins for P II interaction include NtrB, which is part of a two-component regulatory system Reitzer, 2003), and GlnE, which controls the reversible adenylylation of GS (Jiang et al, 1998a;Stadtman, 2001). In diazotrophs P II homologues interact with either NifA or NifL, which directly or indirectly regulates nif expression Jack et al, 1999;Little et al, 2002Little et al, , 2000Rudnick et al, 2002;Stips et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

“…Glutamine synthetase (GS) activity is particularly critical and it is closely regulated transcriptionally and post-translationally, based on the nitrogen status of the cell (Arcondéguy et al, 2001;Stadtman, 2001). There are two sensors of nitrogen status in the enterics, reflecting the pools of two small molecules: nitrogen-rich glutamine and carbon-rich 2-oxoglutarate (a-ketoglutarate, a-KG).…”

Section: Introductionmentioning

confidence: 99%

Effect of AmtB homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in Rhodospirillum rubrum

et al. 2006

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The AmtB protein transports uncharged NH 3 into the cell, but it also interacts with the nitrogen regulatory protein P II , which in turn regulates a variety of proteins involved in nitrogen fixation and utilization. Three P II homologues, GlnB, GlnK and GlnJ, have been identified in the photosynthetic bacterium Rhodospirillum rubrum, and they have roles in at least four overlapping and distinct functions, one of which is the post-translational regulation of nitrogenase activity. In R. rubrum, nitrogenase activity is tightly regulated in response to NH + 4 addition or energy depletion (shift to darkness), and this regulation is catalysed by the post-translational regulatory system encoded by draTG. Two amtB homologues, amtB 1 and amtB 2 , have been identified in R. rubrum, and they are linked with glnJ and glnK, respectively. Mutants lacking AmtB 1 are defective in their response to both NH + 4 addition and darkness, while mutants lacking AmtB 2 show little effect on the regulation of nitrogenase activity. These responses to darkness and NH + 4 appear to involve different signal transduction pathways, and the poor response to darkness does not seem to be an indirect result of perturbation of internal pools of nitrogen. It is also shown that AmtB 1 is necessary to sequester detectable amounts GlnJ to the cell membrane. These results suggest that some element of the AmtB 1 -P II regulatory system senses energy deprivation and a consistent model for the integration of nitrogen, carbon and energy signals by P II is proposed. Other results demonstrate a degree of specificity in interaction of AmtB 1 with the different P II homologues in R. rubrum. Such interaction specificity might be important in explaining the way in which P II proteins regulate processes involved in nitrogen acquisition and utilization.

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“…GS and GLNase are two critical enzymes of nitrogen metabolism that are regulated on numerous levels. The activity of cytosolic GS depends on the intracellular levels of glutamate, ammonium, and ATP and is a subject to cumulative feedback inhibition by more than 40 biosynthetic products of nucleotide synthesis and by adenylation (35). GLNase, which is predominantly localized between outer and inner mitochondrial membranes, is regulated by local glutamine availability but also by the levels of intracellular inorganic phosphate N-acetyl-aspartate, taurine, histidine, lysine, and intermediates of TCA (29,36).…”

Section: Discussionmentioning

confidence: 99%

A simple method for measuring intracellular activities of glutamine synthetase and glutaminase in glial cells

Mongin

Hyzinski‐García

Vincent

et al. 2011

American Journal of Physiology-Cell Physiology

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Mongin AA, Hyzinski-García MC, Vincent MY, Keller RW Jr. A simple method for measuring intracellular activities of glutamine synthetase and glutaminase in glial cells. Am J Physiol Cell Physiol 301: C814-C822, 2011. First published July 6, 2011; doi:10.1152/ajpcell.00035.2011.-Here we report and validate a simple method for measuring intracellular activities of glial glutamine synthetase (GS) and glutaminase (GLNase) in intact glial cells. These enzymes are responsible for glutamate and glutamine recycling in the brain, where glutamate and glutamine transport from the blood stream is strongly limited by the blood-brain barrier. The intracellular levels of glutamate and glutamine are dependent on activities of numerous enzymatic processes, including 1) cytosolic production of glutamine from glutamate by GS, 2) production of glutamate from glutamine by GLNase that is primarily localized between mitochondrial membranes, and 3) mitochondrial conversion of glutamate to the tricarboxylic cycle intermediate ␣-ketoglutarate in the reactions of oxidative deamination and transamination. We measured intracellular activities of GS and GLNase by quantifying enzymatic interconversions of L-[ 3 H]glutamate and L-[ 3 H]glutamine in cultured rat astrocytes. The intracellular substrate and the products of enzymatic reactions were separated in one step using commercially available anion exchange columns and quantified using a scintillation counter. The involvement of GS and GLNase in the conversion of 3 H-labeled substrates was verified using irreversible pharmacological inhibitors for each of the enzymes and additionally validated by measuring intracellular amino acid levels using an HPLC. Overall, this paper describes optimized conditions and pharmacological controls for measuring GS and GLNase activities in intact glial cells.glutamate-glutamine cycle; metabolism; astrocytes L-GLUTAMATE and L-glutamine are two major intermediates of nitrogen metabolism. These two amino acids are present at high micromolar (ϳ30 -500 M) levels in the circulatory system. They diffuse freely from capillaries to the interstitial liquids and extracellular space and are taken inside animal cells by several types of amino acid transporters (24). In cytosol and mitochondrial matrix, concentrations of glutamate and glutamine are in the millimolar range. These two amino acids exist in equilibrium because they are consumed and produced in numerous interrelated biochemical reactions. The abundance and the generic roles of glutamate and glutamine in metabolism and protein synthesis interfere with the signaling properties of glutamate in the central nervous system (CNS). In the brain, glutamate serves as the main excitatory neurotransmitter. Therefore, extracellular levels of glutamate have to be tightly regulated and kept at low levels (reviewed in Refs. 9 and 14). This is possible due to two major factors: 1) limited transport of glutamate and glutamine via the endothelial blood-brain barrier (33), and 2) continuous recycling of glutamate and glutamine in t...

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The Story of Glutamine Synthetase Regulation

Cited by 151 publications

References 49 publications

Fatty Acid Degradation in Escherichia coli

Fatty Acid Degradation in Escherichia coli

Effect of AmtB homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in Rhodospirillum rubrum

A simple method for measuring intracellular activities of glutamine synthetase and glutaminase in glial cells

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