scholarly journals Glutamine synthetase in muscle and kidney

1970 ◽  
Vol 119 (2) ◽  
pp. 145-156 ◽  
Author(s):  
Khalid Iqbal ◽  
J. H. Ottaway
Keyword(s):  
Skeletal Muscle ◽  
Glutamine Synthetase ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Optimum Conditions ◽  
Muscle Enzyme ◽  
Tissue Extracts ◽  
Kidney Enzyme

1. Glutamine synthetase activity has been determined in extracts of rat cardiac and skeletal muscle and kidney, after treatment to ensure that the rate of synthesis was proportional to time of incubation and to amount of extract added. The activity was measured by two methods, with hydroxylamine as substrate. 2. No activity was detected in rat heart extract by either method. The activity in skeletal muscle was of the order of 20μmol of glutamylhydroxamate synthesized/h per g of tissue under optimum conditions. The activity in kidney extracts was 180μmol/h per g of tissue when measured as ferric hydroxamate. 3. The activity in both skeletal-muscle and kidney extracts was inhibited by Pi. The inhibition is competitive for the muscle enzyme, with a Ki of 12mm. For the kidney enzyme the inhibition is non-competitive, and less marked. Possible enzyme mechanisms that would lead to these types of inhibition are discussed. 4. Several observations are reported that suggest that the enzymes from muscle and kidney are not identical. 5. Growth hormone, either in vivo or in vitro, did not affect the measured glutamine synthetase activity of tissue extracts.

scholarly journals In Vivo Regulation of Glutamine Synthetase Activity in the Marine Chlorophyll b-Containing CyanobacteriumProchlorococcus sp. Strain PCC 9511 (Oxyphotobacteria)

2001 ◽  
Vol 67 (5) ◽  
pp. 2202-2207 ◽  
Author(s):  
Sabah El Alaoui ◽  
Jesús Diez ◽  
Lourdes Humanes ◽  
Fermı́n Toribio ◽  
Frédéric Partensky ◽  
...  
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Starvation ◽  
Glutamate Synthase ◽  
Nitrogen Sources ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Determination ◽  
Physiological Regulation ◽  
Gs Protein

ABSTRACT The physiological regulation of glutamine synthetase (GS; EC6.3.1.2 ) in the axenic Prochlorococcus sp. strain PCC 9511 was studied. GS activity and antigen concentration were measured using the transferase and biosynthetic assays and the electroimmunoassay, respectively. GS activity decreased when cells were subjected to nitrogen starvation or cultured with oxidized nitrogen sources, which proved to be nonusable forProchlorococcus growth. The GS activity in cultures subjected to long-term phosphorus starvation was lower than that in equivalent nitrogen-starved cultures. Azaserine, an inhibitor of glutamate synthase, provoked an increase in enzymatic activity, suggesting that glutamine is not involved in GS regulation. Darkness did not affect GS activity significantly, while the addition of diuron provoked GS inactivation. GS protein determination showed that azaserine induces an increase in the concentration of the enzyme. The unusual responses to darkness and nitrogen starvation could reflect adaptation mechanisms of Prochlorococcus for coping with a light- and nutrient-limited environment.

Alterations in glutamine synthetase activity in rat skeletal muscle are associated with advanced age

Nutrition ◽  
2006 ◽  
Vol 22 (7-8) ◽  
pp. 778-785 ◽  
Author(s):  
Carole Pinel ◽  
Véronique Coxam ◽  
Michelle Mignon ◽  
Daniel Taillandier ◽  
Christine Cubizolles ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glutamine Synthetase ◽  
Advanced Age ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Rat Skeletal Muscle

Encapsulation of glutamine synthetase in mouse erythrocytes: a new procedure for ammonia detoxification

2008 ◽  
Vol 86 (6) ◽  
pp. 469-476 ◽  
Author(s):  
Elena A. Kosenko ◽  
Natalia I. Venediktova ◽  
Andrey A. Kudryavtsev ◽  
Fazoil I. Ataullakhanov ◽  
Yury G. Kaminsky ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Glutamine Synthetase ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Cell Recovery ◽  
Ammonia Detoxification ◽  
Neurological Alterations

There are a number of pathological situations in which ammonia levels increase leading to hyperammonemia, which may cause neurological alterations and can lead to coma and death. Currently, there are no efficient treatments allowing rapid and sustained decrease of ammonia levels in these situations. A way to increase ammonia detoxification would be to increase its incorporation in glutamine by glutamine synthetase. The aim of this work was to develop a procedure to encapsulate glutamine synthetase in mouse erythrocytes and to assess whether administration of these erythrocytes containing glutamine synthetase (GS) reduce ammonia levels in hyperammonemic mice. The procedure developed allowed the encapsulation of 3 ± 0.25 IU of GS / mL of erythrocytes with a 70% cell recovery. Most metabolites, including ATP, remained unaltered in glutamine synthetase-loaded erythrocytes (named ammocytes by us) compared with native erythrocytes. The glutamine synthetase-loaded ammocytes injected in mice survived and retained essentially all of their glutamine synthetase activity for at least 48 h in vivo. Injection of these ammocytes into hyperammonemic mice reduced ammonia levels in the blood by about 50%. The results reported indicate that ammocytes are able to keep their integrity, normal energy metabolism, the inserted glutamine synthetase activity, and can be useful to reduce ammonia levels in hyperammonemic situations.

Enzymes of glutamine metabolism in inflammation associated with skeletal muscle hypertrophy

1989 ◽  
Vol 257 (6) ◽  
pp. E885-E894 ◽  
Author(s):  
T. B. Kelso ◽  
C. R. Shear ◽  
S. R. Max
Keyword(s):  
Skeletal Muscle ◽  
Connective Tissue ◽  
Glutamine Synthetase ◽  
Pentose Phosphate Pathway ◽  
Tissue Repair ◽  
Time Course ◽  
Pentose Phosphate ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Plantaris Muscle

Glutamine synthesis and utilization were studied in the plantaris muscle after removal of its functional synergists, the soleus and gastrocnemius muscles. Rat plantaris muscle was compared with unoperated controls at 7, 14, and 30 days after synergist ablation and induction of hypertrophy. Glutamine synthetase activity increased from 6.17 +/- 1.77 to 33.92 +/- 2.23 nmol.h-1.mg protein-1, and glutaminase activities increased from 98.63 +/- 23.05 to 478.70 +/- 64.17 nmol.h-1.mg protein-1 7 days after surgery and remained elevated at 14 and 30 days. Sham-operated controls examined 7 days after surgery did not exhibit significantly increased glutamine synthetase activity. Histological examination revealed a large proliferation of connective tissue cells, as well as cells involved in tissue repair and inflammation; this influx was maximal 1 wk after surgery. The activity of the oxidative enzymes of the pentose phosphate pathway increased from 3.08 +/- 4.31 to 20.86 +/- 1.13 nmol.min-1.mg protein-1 1 wk after surgery. The time course of changes in pentose phosphate pathway enzymes was similar to that of the increases in glutamine synthetase, glutaminase, and cellular infiltration. Increases in muscle wet weight followed a different time course than changes in glutamine synthetase, glutaminase, and pentose phosphate pathway activities. It is concluded that the initial increases in plantaris muscle weight are probably due to edema, connective tissue proliferation, and cells involved in tissue repair and inflammation. The increase in glutamine synthetase activity appears to occur in skeletal muscle, whereas the changes in glutaminase and pentose phosphate pathway activities appear to represent infiltrating inflammatory cells. Furthermore, the increase in glutamine synthetase activity may serve to support the infiltrating cells, which appear to lack substantial capacity for glutamine production. These results represent a functional relationship between skeletal muscle glutamine synthesis and utilization by cells mediating inflammation and connective tissue repair and synthesis.

scholarly journals Glutamine synthetase activity of muscle in acidosis

1983 ◽  
Vol 216 (2) ◽  
pp. 523-525 ◽  
Author(s):  
P A King ◽  
L Goldstein ◽  
E A Newsholme
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Acidosis ◽  
Glutamine Synthetase ◽  
Maximum Activity ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Adrenal Steroids ◽  
Acid Base Balance ◽  
Acid Base ◽  
Base Balance

Metabolic acidosis stimulates the rate of glutamine release from muscle, and this in turn is used by the kidney in acid-base balance. NH4Cl, HCl or diabetic ketoacidosis increases the maximum activity of glutamine synthetase in skeletal muscle. Starvation and administration of adrenal steroids also increase the activity of the enzyme in muscle.

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