In Situ Glutamine Synthetase Activity in a Marine Unicellular Alga (Development of a Sensitive Colorimetric Assay and the Effects of Nitrogen Status on Enzyme Activity)

The distribution of the glutamine metabolizing enzymes was studied in the kidney of four mammalian species (dog, rat, rabbit and guinea pig). Glutaminase I activity of whole kidney was highest in the dog (19.1 µm NH3/gm/min.), intermediate in the rat (8.1 µm NH3/gm/min.), and low in the guinea pig (1.1 µm NH3/ gm/min.) and rabbit (0.6 µm NH3/gm/min.). In all four species, enzyme activity was highest in the cortex and inner medulla. Glutaminase II and glutamine synthetase activity were lower than glutaminase I activity in all four species. Both glutaminase II and glutamine synthetase activity were found only in the cortex and outer medulla. The relationship of the glutamine metabolizing enzymes to the production of urinary ammonia is discussed.

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Glutamine synthetase from Mycobacterium avium

Canadian Journal of Microbiology ◽

10.1139/m84-052 ◽

1984 ◽

Vol 30 (3) ◽

pp. 353-359 ◽

Cited By ~ 9

Author(s):

Maria E. Alvarez ◽

C. M. McCarthy

Keyword(s):

Enzyme Activity ◽

Glutamine Synthetase ◽

Nitrogen Source ◽

Mycobacterium Avium ◽

Specific Activity ◽

Sedimentation Coefficient ◽

Ammonia Assimilation ◽

Methionine Sulfoximine ◽

Synthetase Activity ◽

Glutamine Synthetase Activity

Mycobacterium avium was previously shown to be dependent upon ammonia or glutamine as a nitrogen source. In an effort to assess the physiology of ammonia assimilation by M. avium, a characterization of its glutamine synthetase was performed. The enzyme from M. avium was purified by streptomycin sulfate treatment, ammonium sulfate precipitation, and affinity chromatography. The enzyme was unusual in that it had a pH optimum of 6.4 and maximum enzyme activity was obtained between 50 and 60 °C as shown by the transferase assay. The glutamine synthetase activity from batch-cultured cells decreased with increasing concentration of ammonium chloride in the range of 0.25–5 μ mol/mL of medium, which demonstrated a response to environmental supply of a nitrogen source. The mycobacterial enzyme was similar to the other bacterial glutamine synthetases in terms of molecular weight and sedimentation coefficient which were 600 000 and 19.5 S, respectively, and enzyme activity was lost by treatment with a glutamate analog, methionine sulfoximine. The isoelectric point was, however, pH 4.5. Treatment of the enzyme with snake venom phosphodiesterase resulted in an increase in specific activity. AMP was released by the phosphodiesterase treatment, thus demonstrating that M. avium glutamine synthetase was regulated by adenylylation modification.

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Effect of diabetes on glutamine synthetase expression in rat skeletal muscles

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.258.5.e762 ◽

1990 ◽

Vol 258 (5) ◽

pp. E762-E766 ◽

Cited By ~ 2

Author(s):

B. Feng ◽

C. Banner ◽

S. R. Max

Keyword(s):

Enzyme Activity ◽

Glutamine Synthetase ◽

Skeletal Muscles ◽

Mrna Level ◽

State Level ◽

Diabetic Rats ◽

Synthetase Activity ◽

Glutamine Synthetase Activity ◽

Insulin Administration ◽

Body Weights

The regulation of glutamine synthetase expression in muscles from normal and diabetic (streptozotocin-treated) rats was studied. Muscle and body weights were markedly reduced in diabetic animals. Glutamine synthetase activity was significantly (2-fold) elevated 7 days after induction of diabetes. Increased enzyme activity persisted for at least 14 days after induction of diabetes, and it was apparent in both slow (soleus) and fast (plantaris) muscles. The diabetes-induced increase in enzyme activity was reflected in an increased steady-state level of glutamine synthetase mRNA. The increases in glutamine synthetase activity and mRNA level in muscle from diabetic rats were reversed by insulin administration. Increased expression of glutamine synthetase may be important for accelerated glutamine production by muscle from diabetic rats.

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Reduced Glutamine Synthetase Activity Alters the Fecundity of Female Bactrocera dorsalis (Hendel)

Insects ◽

10.3390/insects10070186 ◽

2019 ◽

Vol 10 (7) ◽

pp. 186 ◽

Cited By ~ 2

Author(s):

Dong Wei ◽

Meng-Yi Zhang ◽

Ying-Xin Zhang ◽

Su-Yun Zhang ◽

Guy Smagghe ◽

...

Keyword(s):

Gene Expression ◽

Enzyme Activity ◽

Glutamine Synthetase ◽

Egg Production ◽

Fat Body ◽

Specific Inhibitor ◽

Bactrocera Dorsalis ◽

Transcriptional Level ◽

Synthetase Activity ◽

Glutamine Synthetase Activity

Glutamine synthetase (GS) is a key enzyme in glutamine synthesis and is associated with multiple physiological processes in insects, such as embryonic development, heat shock response, and fecundity regulation. However, little is known about the influence of GS on female fecundity in the oriental fruit fly, Bactrocera dorsalis. Based on the cloning of BdGSs, mitochondrial BdGSm and cytoplasmic BdGSc, we determined their expressions in the tissues of adult B. dorsalis. BdGSm was highly expressed in the fat body, while BdGSc was highly expressed in the head and midgut. Gene silencing by RNA interference against two BdGSs isoforms suppressed target gene expression at the transcriptional level, leading to a reduced ovarian size and lower egg production. The specific inhibitor L-methionine S-sulfoximine suppressed enzyme activity, but only the gene expression of BdGSm was suppressed. A similar phenotype of delayed ovarian development occurred in the inhibitor bioassay. Significantly lower expression of vitellogenin and vitellogenin receptor was observed when GS enzyme activity was suppressed. These data illustrate the effects of two GS genes on adult fecundity by regulating vitellogenin synthesis in different ways.

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Neural control of glutamine synthetase activity in rat skeletal muscles

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.258.5.e757 ◽

1990 ◽

Vol 258 (5) ◽

pp. E757-E761 ◽

Cited By ~ 1

Author(s):

B. Feng ◽

M. Konagaya ◽

Y. Konagaya ◽

J. W. Thomas ◽

C. Banner ◽

...

Keyword(s):

Enzyme Activity ◽

Glutamine Synthetase ◽

Neural Control ◽

Control Level ◽

Maximum Velocity ◽

State Level ◽

Male Rats ◽

Synthetase Activity ◽

Glutamine Synthetase Activity ◽

Limb Immobilization

The mechanism of glutamine synthetase induction in rat skeletal muscle after denervation or limb immobilization was investigated. Adult male rats were subjected to midthigh section of the sciatic nerve. At 1, 2, and 5 h and 1, 2, and 7 days after denervation, rats were killed and denervated, and contralateral control soleus and plantaris muscles were excised, weighted, homogenized, and assayed for glutamine synthetase. Glutamine synthetase activity increased approximately twofold 1 h after denervation in both muscles. By 7 days postdenervation enzyme activity had increased to three times the control level in plantaris muscle and to four times the control level in soleus muscle. Increased enzyme activity after nerve section was associated with increased maximum velocity with no change in apparent Michaelis constant. Immunotitration with an antiglutamine synthetase antibody suggested that denervation caused an increase in the number of glutamine synthetase molecules in muscle. However, Northern-blot analysis revealed no increase in the steady-state level of glutamine synthetase mRNA after denervation. A mixing experiment failed to yield evidence for the presence of a soluble factor involved in regulating the activity of glutamine synthetase in denervated muscle. A combination of denervation and dexamethasone injections resulted in additive increases in glutamine synthetase. Thus the mechanism underlying increased glutamine synthetase after denervation appears to be posttranscriptional and is distinct from that of the glucocorticoid-mediated glutamine synthetase induction previously described by us.

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CORRESPONDENCE BETWEEN GLUTAMINE SYNTHETASE ACTIVITY AND DIFFERENTIATION IN THE EMBRYONIC RETINA IN SITU AND IN CULTURE

The Journal of Cell Biology ◽

10.1083/jcb.27.1.247 ◽

1965 ◽

Vol 27 (1) ◽

pp. 247-252 ◽

Cited By ~ 61

Author(s):

Ronald Piddington ◽

A. A. Moscona

Keyword(s):

Glutamine Synthetase ◽

Synthetase Activity ◽

Glutamine Synthetase Activity ◽

Embryonic Retina

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A Thioredoxin Activated Glutamine Synthetase in Chlorella

Zeitschrift für Naturforschung C ◽

10.1515/znc-1981-5-609 ◽

1981 ◽

Vol 36 (5-6) ◽

pp. 396-399 ◽

Cited By ~ 12

Author(s):

Ahlert Schmidt

Keyword(s):

Enzyme Activity ◽

Glutamine Synthetase ◽

Chlorella Pyrenoidosa ◽

Specific Role ◽

Synthetase Activity ◽

Glutamine Synthetase Activity ◽

Synechococcus 6301 ◽

Full Activation

Abstract Glutamine synthetase was partly purified from Chlorella pyrenoidosa. This enzyme activity was stimulated by dithioerythritol and 2′-3′-dim ercaptopropanol (BAL). Full activation was obtained by thioredoxins isolated from the cyanobacterium Synechococcus 6301, from spinach and by heated Chlorella extract. The apparent Km for the purified thioredoxin B from Synechococcus 6301 was determined to be 0.022 (22 × 10-9 M), suggesting a specific role for thioredoxins in regulating glutamine synthetase activity in this alga.

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