Regulation of Glutaminase Activity and Glutamine Metabolism

1995 ◽  
Vol 15 (1) ◽  
pp. 133-159 ◽  
Author(s):  
Norman P. Curthoys ◽  
Malcolm Watford
Keyword(s):  
Glutamine Metabolism ◽  
Glutaminase Activity

scholarly journals The regulation of phosphate-activated glutaminase activity and glutamine metabolism in the streptozotocin-diabetic rat

1984 ◽  
Vol 224 (1) ◽  
pp. 207-214 ◽  
Author(s):  
M Watford ◽  
E M Smith ◽  
E J Erbelding
Keyword(s):  
Drinking Water ◽  
Small Intestine ◽  
Glutamine Metabolism ◽  
Diabetic Rat ◽  
Complete Suppression ◽  
Chemically Induced ◽  
Phosphate Activated Glutaminase ◽  
Kidney Liver ◽  
Nh4cl Solution ◽  
Glutaminase Activity

The activity of phosphate-activated glutaminase was increased in the kidney, liver and small intestine of rats made diabetic for 6 days with injection of streptozotocin (75 mg/kg body wt.). Insulin prevented this increase in all three tissues. Treatment with NaHCO3, to correct the acidosis that accompanies diabetes, prevented the increase in renal glutaminase activity, but not that in liver or small intestine. Chemically induced acidosis (NH4Cl solution as drinking water) or alkalosis (NaHCO3 solution as drinking water) increased and decreased, respectively, glutaminase activity in the kidney, but were without significant effect on the activity in liver and small intestine. The increase in glutaminase activity in the small intestine during diabetes was due to an overall increase in the size of this organ, and was only detectable when activity was expressed in terms of whole organ, not mucosal scrapings or isolated enterocytes. Prolonged diabetes (40 days) resulted in an even greater increase in the size and glutaminase activity of the small intestine. Despite this marked increase in capacity for glutamine catabolism, arteriovenous-difference measurements showed a complete suppression of plasma glutamine utilization by the small intestine during diabetes, confirming the report by Brosnan, Man, Hall, Colbourne & Brosnan [(1983) Am. J. Physiol. 235, E261-E265].

Extracellular glutamate flux regulates intracellular glutaminase activity in LLC-PK1-F+ cells

1995 ◽  
Vol 268 (6) ◽  
pp. C1418-C1424 ◽  
Author(s):  
T. C. Welbourne ◽  
X. Mu
Keyword(s):  
Time Course ◽  
Glutamate Uptake ◽  
Fold Increase ◽  
Cellular Level ◽  
Glutamine Metabolism ◽  
Apical Surface ◽  
Extracellular Glutamate ◽  
Basal Surface ◽  
F Cells ◽  
Glutaminase Activity

The role of extracellular glutamate flux in regulating intracellular glutaminase activity was assessed in confluent monolayers of proximal tubule-like LLC-PK1-F+ cells grown on porous supports. Glutamate is a well-known inhibitor of phosphate-dependent glutaminase (PDG). We hypothesized that, by restricting the flux of glutamate from the extracellular media, cellular level would fall, effecting deinhibition of the cellular glutaminase activity. To test this, cellular glutamate uptake and extracellular production were inhibited for 18 h by the addition of D-aspartate (10 mM) or acivicin (0.7 mM) to both apical and basal media. Inhibiting glutamate flux depressed cellular glutamate content 43 and 41%, respectively. Intracellular relative glutaminase activity, monitored as the breakdown of 14C-radiolabeled glutamine to glutamate, measured over 60 s in the presence of D-aspartate or acivicin showed a 2- to 2.5-fold increase with the fall in cellular glutamate. Interestingly, enhanced glutamine uptake after PDG deinhibition was predominantly expressed on the basal surface. Indeed, measuring glutamine utilization after gamma-glutamyltranspeptidase inhibition over the entire 18-h time course revealed inhibition at the apical surface but relative enhancement of uptake at the basal surface. The increased intracellular glutaminase pathway was also reflected in increased alanine production measured over the 18-h time course, despite the reduction in overall glutamine utilization. These results point to a major role for extracellular glutamate fluxes in regulating cellular glutamine metabolism and suggest that the intracellular pathway may be suppressed under these conditions.

Glutamine transport in submitochondrial particles

1989 ◽  
Vol 257 (6) ◽  
pp. F1050-F1058 ◽  
Author(s):  
S. Sastrasinh ◽  
M. Sastrasinh
Keyword(s):  
Metabolic Acidosis ◽  
Glutamine Metabolism ◽  
Hill Coefficient ◽  
Submitochondrial Particles ◽  
Multiple Binding Sites ◽  
Cooperativity Effect ◽  
Multiple Binding ◽  
Glutamine Transport ◽  
Glutaminase Activity ◽  
Glutamine Uptake

Glutamine transport was studied in submitochondrial particles (SMP) to avoid interference from glutamine metabolism. Phosphate-dependent glutaminase activity in SMP was only 0.04% of that in intact mitochondria. The uptake of glutamine in SMP represented both the transport into vesicles and membrane binding (about one-third of total uptake). Sulfhydryl reagents inhibited glutamine uptake in SMP. The uptake of L-[3H]glutamine increased more than twofold in SMP preloaded with 1 mM L-glutamine, an effect that was not seen with 1 mM D-glutamine. The uptake of L-[3H]glutamine was inhibited in the presence of either L-glutamine or L-alanine in the incubation medium. Other amino acids did not inhibit glutamine uptake. Alanine was also shown to trans-stimulate glutamine transport in SMP and cis-inhibit glutamine transport in both SMP and intact mitochondria. Glutamine transport showed a positive cooperativity effect with a Hill coefficient of 1.45. Metabolic acidosis increased the affinity of the transporter for glutamine without any change in other kinetic parameters. These data indicated that mitochondrial glutamine transport occurs via a specific carrier with multiple binding sites and that the transport of glutamine into mitochondria has an important role in increased ammoniagenesis during metabolic acidosis.

Effects of adrenaline on glucose and glutamine metabolism and superoxide production by rat neutrophils

1999 ◽  
Vol 96 (6) ◽  
pp. 549-555 ◽  
Author(s):  
Carolina GARCIA ◽  
Tania C. PITHON-CURI ◽  
Maria DE LOURDES FIRMANO ◽  
Mariza PIRES DE MELO ◽  
Philip NEWSHOLME ◽  
...  
Keyword(s):  
Large Body ◽  
Inhibitory Effect ◽  
Pentose Phosphate ◽  
Superoxide Production ◽  
Glutamine Metabolism ◽  
Protective Mechanism ◽  
Dibutyryl Camp ◽  
Phagocytic Capacity ◽  
Glutaminase Activity

Despite the large body of information on the role of corticosteroids in regulating lymphocyte and phagocyte function, the role of the hormone adrenaline in immunoregulation is an under-investigated topic. The present study has addressed the effects of adrenaline on the rates of utilization and oxidation of glucose and glutamine, the phagocytic capacity and the rate of superoxide production by rat neutrophils. Incubation of rat neutrophils in the presence of 50 µM adrenaline caused a marked elevation in glucose metabolism, an effect that could be blocked by propranolol. Adrenaline caused a partial inhibition of glutamine utilization by neutrophils, an effect that was also blocked by propranolol. These effects of adrenaline could be mimicked by 100 µM dibutyryl cAMP. Phosphate-dependent glutaminase activity was significantly elevated in neutrophils incubated in the presence of 50 µM adrenaline or 100 µM dibutyryl cAMP for 1 h, whereas glutamine oxidation was significantly depressed (P < 0.05) under these conditions. The elevation in enzyme activity was only partially blocked by propranolol. The phagocytic activity of rat neutrophils was not altered by adrenaline in the presence of either glucose or glutamine. The rate of phorbol 12-myristate 13-acetate-induced superoxide production in the presence of glucose was potently reduced by the addition of 5 nM or 50 µM adrenaline. This effect could be mimicked by dibutyryl cAMP. However, when rat neutrophils were incubated in the presence of glutamine plus adrenaline (5 nM or 50 µM), the rate of superoxide production was only marginally reduced. These findings support the proposition that adrenaline may deviate the flux of glucose from the NADPH-producing pentose phosphate pathway, thus reducing substrate availability for the superoxide-generating NADPH oxidase. However, glutamine metabolism may still give rise to substantial quantities of NADPH from the glutaminolysis pathway. We postulate that glutamine metabolism may thus provide a protective mechanism against the inhibitory effect of adrenaline on superoxide production by neutrophils.

Renal ammonium production—une vue canadienne

1987 ◽  
Vol 65 (4) ◽  
pp. 489-498 ◽  
Author(s):  
J. T. Brosnan ◽  
M. Lowry ◽  
P. Vinay ◽  
A. Gougoux ◽  
M. L. Halperin
Keyword(s):  
Metabolic Acidosis ◽  
Glutamine Metabolism ◽  
Ammonium Excretion ◽  
Acid Base Balance ◽  
Acid Base ◽  
Base Balance ◽  
Ammonium Production ◽  
Alternate Fuels ◽  
Glutaminase Activity ◽  
Stimulation Of

The purpose of this review is to examine the factors regulating ammonium production in the kidney and to place these factors in the perspective of acid–base balance. Renal ammonium production and excretion are required to maintain acid–base balance. However, only a portion of renal ammonium production is specifically stimulated by metabolic acidosis. One should examine urinary ammonium excretion at three levels: distribution of ammonium between blood and urine, augmented glutamine metabolism, and an energy constraint due to ATP balance considerations. With respect to the biochemical regulation of acid–base renal ammonium production, an acute stimulation of α-ketoglutarate dehydrogenase by a fall in pH seems to be important but this may not be the entire story. In chronic metabolic acidosis augmented glutamine entry into mitochondria (dog) or increased phosphate-dependent glutaminase activity (rat) become critical to support a high flux rate. Metabolic alterations, which diminish the rate of oxidation of alternate fuels, might also be important. The above principles are discussed in the ketoacidosis of fasting, the clinically important situation of high rates of renal ammonium production.

Hormonal control of macrophage function and glutamine metabolism

1991 ◽  
Vol 69 (4) ◽  
pp. 309-312 ◽  
Author(s):  
L. F. B. P. Costa Rosa ◽  
Y. Cury ◽  
R. Curi
Keyword(s):  
Thyroid Hormones ◽  
Hormonal Control ◽  
Glutamine Metabolism ◽  
Macrophage Function ◽  
Murine Macrophages ◽  
Inflammatory Macrophages ◽  
Glutaminase Activity

Murine macrophages have been reported to utilize glutamine at high rates. However, the role of glutamine in macrophage function is still unknown. In the present study, the maximum glutaminase activity of macrophages was investigated under several endocrine dysfunctions that are known to cause alterations in macrophage function. The results obtained suggest that glutamine might play an important role in the onset of phagocytosis in inflammatory macrophages. Moreover, the studies show that insulin, glucocorticoids, and thyroid hormones may be responsible for the regulation of glutamine metabolism and, consequently, of macrophage function.Key words: macrophage, glutamine, insulin, glucocorticoids, thyroid hormones, catecholamines.

scholarly journals Glutamine metabolism in isolated incubated adipocytes of the rat

1988 ◽  
Vol 249 (3) ◽  
pp. 705-708 ◽  
Author(s):  
J M Kowalchuk ◽  
R Curi ◽  
E A Newsholme
Keyword(s):  
Adipose Tissue ◽  
Glucose Concentration ◽  
Glutamine Metabolism ◽  
Fat Pad ◽  
Lean Control ◽  
Epididymal Fat ◽  
End Products ◽  
Glutaminase Activity ◽  
Alanine Production

1. Phosphate-dependent glutaminase activity in the epididymal fat-pad was 15.1 nmol/min per mg of protein. Glutaminase activity demonstrated differences with respect to adipose-tissue sites. Considerable variation was found in different sites of adipose tissue from lean control and Zucker obese animals. 2. Adipocytes incubated in the presence of 2 mM-glutamine utilized glutamine at a rate of 1.8 mumol/h per g dry wt., and glutamate, ammonia, lactate and alanine were produced. Addition of glucose plus insulin increased the rates of glutamine utilization and glutamate, ammonia, lactate and alanine production. Isoprenaline alone or plus glucose further stimulated the rate of glutamine utilization and formation of end products. 3. The rate of incorporation of 14C from glutamine into CO2 was similar to that of glucose, but the rate of incorporation into triacylglycerol was much less. Addition of unlabelled glucose or glucose plus insulin stimulated the rate of incorporation of [14C]glutamine into triacylglycerol, but had no effect on that of 14CO2 formation. Isoprenaline plus glucose increased the rate of incorporation of [14C]glutamine into CO2, but decreased the rate of incorporation into triacylglycerol. 4. In the absence of insulin, the rate of [14C]glutamine incorporation into triacylglycerol was related to the glucose concentration (0-10 mM). However, in the presence of insulin, the rate of incorporation of [14C]glutamine was maximal at 1 mM-glucose.

scholarly journals Glutamine metabolism in skeletal muscles from the broiler chick (Gallus domesticus) and the laboratory rat (Rattus norvegicus)

1991 ◽  
Vol 274 (3) ◽  
pp. 769-774 ◽  
Author(s):  
G Wu ◽  
J R Thompson ◽  
V E Baracos
Keyword(s):  
Skeletal Muscle ◽  
Rattus Norvegicus ◽  
Skeletal Muscles ◽  
Species Difference ◽  
Plasma Concentrations ◽  
Subcellular Location ◽  
Glutamine Metabolism ◽  
Oxidative Decarboxylation ◽  
Rat Skeletal Muscle ◽  
Glutaminase Activity

Oxidative decarboxylation of L-[1-14C]glutamine was studied in isolated chick and rat skeletal muscles incubated in the presence of glucose, insulin and plasma concentrations of amino acids. (1) The rate of oxidative decarboxylation of L-[1-14C]glutamine was high, and exceeded that of L-[1-14C]leucine in all muscles. (2) The rate of oxidative decarboxylation of L-[1-14C]glutamine increased with increasing intracellular concentrations of glutamine. (3) The activities of glutamine aminotransferases K and L were more than 10-fold greater in rat than in chick skeletal muscles. (4) Mitochondrial phosphate-activated glutaminase activity was approx. 10-fold greater in chick than in rat skeletal muscles and increased with increasing glutamine concentrations. (5) An inhibitor of glutaminase, 6-diazo-5-oxo-L-norleucine, inhibited the rate of glutamine decarboxylation in chick, but not in rat, skeletal muscle. These findings suggest that glutamine degradation in skeletal muscle may be substantial and may make an important contribution to the regulation of intramuscular glutamine concentrations. A species difference in the pathways and the subcellular location for the conversion of glutamine into 2-oxoglutarate in rat and chick skeletal muscles is implied by the relative activities of glutamine-degrading enzymes.

Importance of glutamine metabolism in murine macrophages and human monocytes to L-arginine biosynthesis and rates of nitrite or urea production

1998 ◽  
Vol 95 (4) ◽  
pp. 397-407 ◽  
Author(s):  
Colin MURPHY ◽  
Philip NEWSHOLME
Keyword(s):  
Urea Cycle ◽  
De Novo ◽  
Mononuclear Phagocytes ◽  
Glutamine Metabolism ◽  
Human Monocytes ◽  
Activated Macrophages ◽  
Arginine Biosynthesis ◽  
Nitrite Production ◽  
Oxide Synthase ◽  
Glutaminase Activity

1.The intermediates of biochemical cycles are commonly utilized for biosynthetic processes; thus at least one intermediate must be replenished de novo to provide constant flux through the cycle. The utilization of l-arginine for NO synthesis in macrophages may thus reduce the concentration of intermediates of the urea cycle. It is possible that a glutamine-utilizing pathway exists in mononuclear phagocytes that may connect with the urea cycle. 2.In this paper we report that mouse peritoneal resident and Bacillus Calmette–Guerin (BCG)-activated macrophages and human monocytes are capable of utilizing glutamine at high rates, contain sufficient activity of the enzymes required to convert glutamine to citrulline (and subsequently citrulline to arginine) to account for observed rates of nitrite synthesis in the absence of extracellular l-arginine, and will release nitrite when exposed to intermediates of the proposed glutamine → arginine pathway. 3.The rate of nitrite production (in the absence of extracellular arginine) was reduced by culturing macrophages or monocytes in the presence of the glutaminase inhibitor 6-diazo 5-oxo norleucine. 4.The rate and extent of arginase secretion, glutamine utilization, nitrite production (basal and lipopolysaccharide-stimulated) and phosphate-dependent glutaminase activity from BCG-activated macrophages was increased compared with resident cells. 5.We suggest that the elevated arginase secretion rates in activated macrophages would effectively increase the intracellular concentration of arginine available for conversion to NO via inducible nitric oxide synthase, the expression of which is known to increase on activation of macrophages or monocytes. Additionally, the rate of l-arginine biosynthesis from glutamine may be increased on immunostimulation of the macrophage.

scholarly journals Glutamine metabolism in the gastrointestinal tract of the rat assessed by the relative activities of glutaminase (EC 3.5.1.2) and glutamine synthetase (EC 6.3.1.2)

1998 ◽  
Vol 79 (4) ◽  
pp. 365-372 ◽  
Author(s):  
L. A. James ◽  
P. G. Lunn ◽  
M. Elia
Keyword(s):  
Small Intestine ◽  
Glutamine Synthetase ◽  
Complete Information ◽  
Total Activity ◽  
External Source ◽  
Glutamine Metabolism ◽  
Gi Tract ◽  
Glutamine Synthesis ◽  
Low Levels ◽  
Glutaminase Activity

The activities of the two key enzymes involved in glutamine metabolism, glutaminase (EC 3.5.1.2) and glutamine synthetase (EC 6.3.1.2), have been measured in the various tissues of the gastrointestinal (GI) tract of the rat, from the mouth to the rectum. Glutaminase activity was particularly high in the mucosa of the small intestine, where its activity accounted for more than 80% of the total activity of the GI tract. In contrast, the mouth and oesophagus had very low activities, accounting for less than 2% of the total. Glutamine synthetase was mainly confined to the lower part of the stomach, which accounted for almost 90% of the total activity of the GI tract. Activity in the small intestine was very low, accounting for less than 2% of the total, and similarly low levels were found in the mouth and oesophagus. The data provide the most complete information on the distribution of these enzymes in the GI tract of the rat and suggest: (a) that the mucosa of the small intestine has the highest capacity for glutamine breakdown but the lowest capacity for its synthesis, and so requires an external source of this amino acid; (b) that there is little potential for glutamine synthesis or breakdown in the mouth and oesophagus; and (c) that the lower stomach has a substantial capacity to synthesize glutamine, in contrast to the rest of the GI tract. The results of the investigation are relevant to sites of glutamine metabolism in therapeutic studies involving glutamine administration discussed with reference to reports of the effects of glutamine administration on GI tract injury.

Sign in / Sign up

Export Citation Format

Share Document