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PubMed1999

Glutamine and transforming growth factor-alpha stimulate extracellular regulated kinases and enhance recovery of villous surface area in porcine ischemic-injured intestine.

BACKGROUND: Epidermal growth factor (EGF) signals enterocyte proliferation via extracellular regulated kinases (ERKs). Because glutamine is required for EGF-stimulated proliferation and stimulates ERKs in intestinal cell culture, we hypothesized that glutamine and the EGF-related peptide transforming growth factor-alpha (TGF-alpha) would synergistically enhance repair associated with stimulation of ERKs. METHODS: Thiry-Vella loops were created in juvenile pigs. One half of the loop was subjected to 2 hours of ischemia, and the other half served as control. Loops were infused daily with Ringer's solution containing 140 mmol/L glucose, 140 mmol/L glutamine, 140 mmol/L glucose plus 60 micrograms/L TGF-alpha, or 140 mmol/L glutamine plus 60 micrograms/L TGF-alpha. RESULTS: After 2 hours of ischemia, complete villous epithelial sloughing was present. By 18 hours, villous epithelium had fully restituted, but villi remained stunted until 144 hours after injury. Glutamine + TGF-alpha triggered sustained increases in ERK activity compared with glucose-treated tissues (maximal at 18 hours), whereas glutamine alone or glucose + TGF-alpha caused only transient elevations in ERK activity. By 72 hours, villous surface area had increased to normal values with glutamine plus TGF-alpha treatment, whereas villi remained stunted with glucose alone, glutamine alone, or glucose plus TGF-alpha. CONCLUSIONS: Glutamine plus TGF-alpha treatment restored mucosal architecture within 72 hours of severe ischemic injury associated with sustained elevations in ERK activity.

Animals↗
PubMed1999

Phagocyte functions in stressed rats: comparison of modulation by glutamine, arginine and ornithine 2-oxoglutarate.

The effects of diets supplemented with 6.8 mmol.day-1.kg-1 glutamine, arginine or ornithine 2-oxoglutarate [ornithine alpha-ketoglutarate (OKG), a precursor of both glutamine and arginine] on phagocyte functions [i.e. H2O2 production by leucocytes and secretion of tumour necrosis factor alpha (TNFalpha) by stimulated macrophages] of stressed rats were studied. The relationship between the immunological effects of these amino acids and their plasma and tissue (muscle and intestine) concentrations was also explored. The catabolic model used consisted of injections of dexamethasone (DEX; 1.5 mg.day-1.kg-1) for 5 days. As previously described, DEX suppressed TNFalpha secretion in stimulated macrophages. Supplementation with arginine or OKG, but not glutamine, was able to counteract the DEX effect on TNFalpha secretion. Glutamine, arginine and OKG supplementation increased H2O2 production by monocytes and polymorphonuclear neutrophils from DEX-treated rats. All DEX-treated rats showed plasma and muscle glutamine depletion and also a decrease in the concentration of arginine in the gastrocnemius. Supplementation with glutamine, arginine or OKG was not able to counteract these depletions. It was concluded that glutamine, arginine and OKG improve phagocyte responses during stress, and that glutamine depletion is not necessarily associated with dysimmunity, since no correlation between glutamine tissue pools and the immune state was observed.

Amino Acids↗
PubMed1999

Induction of gadd153 mRNA by nutrient deprivation is overcome by glutamine.

The growth arrest and DNA damage-inducible (gadd) genes are co-ordinately activated by a variety of genotoxic agents and/or growth-cessation signals. The regulation of gadd153 mRNA was investigated in renal proximal tubular epithelial cells (LLC-PK1) cultured in a nutrient- and serum-deprived medium. The addition of glutamine alone to LLC-PK1 cells cultured in Earl's balanced salt solution (EBSS) is sufficient to suppress gadd153 mRNA expression, and the removal of only glutamine from Dulbecco's modified Eagle's medium (DMEM) is also sufficient to induce gadd153 mRNA expression. Consistent with these findings, the inhibition of glutamine utilization with acivicin and 6-diazo-5-oxo-l-norleucine (DON) in cells grown in a glutamine-containing medium effectively induces gadd153 expression. Glutamine can be used as an energy source in cultured mammalian cells. However, it is unlikely that deficits in cellular energy stores (ATP) are coupled to gadd153 mRNA expression, because concentrations of ATP, UTP and GTP are all elevated in EBSS-exposed cells, and the addition of alpha-oxoglutarate to cells grown in EBSS has no effect on gadd153 mRNA expression. In contrast, concentrations of CTP decline substantially in EBSS and glutamine-deprived DMEM-cultured cells. Glutamine also serves as a precursor for the synthesis of protein and DNA. The addition of glutamine to cells grown in EBSS partly restores CTP concentrations. The addition of pyrimidine ribonucleosides (cytidine and uridine) to LLC-PK1 cells also restores CTP concentrations, in a manner commensurate with their relative abilities to overcome gadd153 expression. Finally, glutamine does not completely suppress DNA damage-induced gadd153 expression, suggesting that multiple signalling pathways lead to the expression of gadd153 mRNA under conditions of nutrient deprivation and DNA damage.

Animals↗
PubMed2000

Glycyl-glutamine improves in vitro lymphocyte proliferation in AIDS patients.

BACKGROUND: Glutamine (Gln) is a major nutrient for rapidly proliferating cells. Unlike glutamine itself, the dipeptide glycyl-glutamine as a source for Gln is stable in aqueous solutions ex vivo. In order to evaluate the possible therapeutic role of glycyl-glutamine on lymphocyte proliferation we investigated its influence on lymphocytes of AIDS patients and healthy controls under stimulation with different mitogens. MATERIAL AND METHODS: Lymphocytes were collected from 11 adult patients suffering from AIDS according to the CDC definition and from 7 adult healthy donors. Glutamine (Gln) and glycyl-glutamine (GlyGln), respectively, were added to cell cultures at concentrations between 0 and 1.0 mmol/l. ConA or SAC served as T or B cell mitogens, respectively. Plasma amino acid levels were determined. RESULTS: Proliferation upon ConA-stimulation with GlyGln-supplementation was similar to Gln-supplementation and peaked dose dependently at 1.0 mmol/l. When SAC was used Gln seemed slightly superior to GlyGln with a peak at 0. 4 mmol/l but the results did not reach the level of statistical significance. An identical response pattern was demonstrated in HIV-patients, however at lower absolute proliferation rates. Normal values could not be restored. Overall, the use of either source of glutamine in equimolar concentrations did not result in major differences of proliferation. Glutamine and glycin plasma levels did not differ between HIV patients and controls. CONCLUSION: GlyGln can be used as a substitute for Gln with regard to lymphocyte proliferation. Lymphocytes from AIDS patients show, as controls do, an enhanced proliferation under supplementation either glutamine source. Supplementation of GlyGln might enhance lymphocyte proliferation and thus improve immunity.

Acquired Immunodeficiency Syndrome↗
PubMed1999

The metabolic fate of the amido-N group of glutamine in the tissues of the gastrointestinal tract in 24 h-fasted sheep.

Whole-body and gastrointestinal tract (GIT) metabolism of [5-(15)N]glutamine were monitored in lambs (33 kg live weight) fasted for 24 h. Animals were previously prepared with vascular catheters across the mesenteric-(MDV) and portal-drained viscera (PDV) to permit quantification of mass and isotopic transfers of metabolites by arterio-venous difference. Continuous infusions of [5-(15)N]glutamine into the jugular vein were conducted for 10 h and integrated blood samples withdrawn over 75 min intervals for the last 5 h of infusion. The lambs were then killed and portions from various tissues of the digestive tract and other body organs removed for determination of 15N enrichment in RNA, DNA and protein (the latter obtained by difference using total acid-precipitable N). Whole-body glutamine flux was 108 mumol/min of which 23 and 47% could be attributed to MDV and PDV metabolism (P < 0.001) respectively. There was a small net production of glutamine across the MDV. GIT blood-flows and NH3 production were partitioned 3:2 between MDV and non-MDV components. Less than 5% of the NH3 produced was derived from the amido-N of glutamine, while across the small intestine (MDV) 26% of the glutamine flux was converted to NH3, compared with 18% for non-MDV transfers. The 15N enrichments in protein were of the order jejunum > duodenum > ileum with mucosal cells more labelled than serosal (P < 0.001). Lesser enrichments were observed for other GIT tissues (abomasum > caecum > rumen) while liver and lymph were comparable with the abomasum; kidney, spleen and muscle were lower still (P < 0.05). Enrichments of RNA were similar to that of protein and followed the same pattern, except for higher relative values for liver, spleen and lymphoid tissue. The lowest enrichments were observed for DNA, but again the pattern order was similar except for increased label in lymph, caecum and the spleen. For the MDV there was reasonable agreement between 15N-disappearance as glutamine and appearance in NH3 (24%), protein (81%), RNA (3.6%) and DNA (2.1%). For the total PDV there was a shortfall (-12%), however, which may be due to losses in lumen components. These results show the importance of the GIT as a contributor to total glutamine plasma flux, but indicate a lesser reliance on glutamine metabolism by the digestive tract of the ruminant compared with observations from non-ruminants.

Ammonia↗
PubMed2001

Sequential changes in in vivo muscle and liver protein synthesis and plasma and tissue glutamine levels in sepsis in the rat.

We have investigated sequential changes in skeletal muscle and hepatic protein synthesis following sepsis, and their relationship to changes in circulating and tissue glutamine concentrations. Male Wistar rats underwent caecal ligation and puncture (CLP) or sham operation, with starvation, and were killed 24, 72 or 96 h later. A group of non-operated animals were killed at the time of surgery. Protein synthesis was determined using a flooding dose of L-[4-(3)H] phenylalanine, and glutamine concentrations were measured by an enzymic fluorimetric assay. Protein synthesis in gastrocnemius muscle fell in all groups. Gastrocnemius total protein content was reduced after CLP and at 72 and 96 h after sham operation. After CLP, protein synthesis was lower at 24 h, and total protein content was lower at 72 and 96 h, than in sham-operated animals. CLP was associated with increased liver protein synthesis at all time points, whereas there was no change after sham operation. Liver protein content did not change after CLP, but was lower at 72 and 96 h after sham operation than in non-operated animals. Plasma glutamine concentrations were reduced at 24 h after sham operation, and at 72 and 96 h after CLP. Muscle glutamine concentrations were reduced in all groups, with the decrease being greater following CLP than after sham operation. In the liver, glutamine concentrations were unchanged after CLP, but increased after sham operation. In rats with sepsis, decreases in muscle protein synthesis and content are associated with markedly reduced muscle glutamine concentrations. Plasma glutamine concentrations are initially maintained, but fall later. In liver, protein synthesis is increased, while glutamine concentrations are preserved. These results support a peripheral-to-splanchnic glutamine flux in sepsis.

Animals↗
PubMed2001

[Studies on regulation of glutamine synthetase activity from Streptomyces lincolnensis].

Glutamine synthetase in crude extracts from Streptomyces lincolnensis growing under different nitrogen sources were studied. The results showed that NH4+ in high concentration repressed the biosynthesis of the enzyme. To determine whether Streptomyces lincolnensis has undergone covalent modification, a comparison of the glutamine synthetase isolated from cells grown on different nitrogen sources was made. No significant difference was observed in specific activity, pH optima, divalent cation response, and ultraviolet absorption spectra. Glutamine synthetase activity was not influenced by ammonia shock or snake venom phosphodiesterase treatment. Under these conditions, the activity of glutamine synthetase from K. aerogenes was markedly changed. There was therefore no evidence for enzymatic adenylylation of glutamine synthetase from Streptomyces lincolnensis. Glutamine synthetase was subject to feedback inhibition by end products of glutamine metabolism. Cumulative feedback inhibition of the Mn(2+)-dependent glutamine synthetase activity was demonstrated. These results suggest that glutamine synthetase from Streptomyces lincolnensis is an allosteric enzyme.

Ammonia↗
PubMed1992

Arteriovenous differences for glutamine in the equine gastrointestinal tract.

Glutamine has been shown to be an important metabolic substrate of enterocytes in many animals, including cats, dogs, hamsters, human beings, monkeys, rabbits, rats, and sheep. To determine whether glutamine is important in the metabolism of cells of the equine gastrointestinal tract, we examined transintestinal differences in glutamine concentrations in the arterial and venous circulation, and measured activity of the major glutamine catabolizing enzyme, glutaminase. Arteriovenous differences provide an index of the amount of a given substrate removed by the tissue across which the measurements are made, and commonly are expressed as a percentage of substrate removed, or percent extraction. Arteriovenous differences for glutamine were determined in 7 anesthetized adult horses (weight, 450 to 500 kg) before and after an i.v. glutamine infusion. The mean baseline arterial glutamine concentration (+/- SEM) was 572 +/- 24 microM; this concentration quadrupled (to 2,167 +/- 135 microM, P less than 0.01) 1 minute after i.v. bolus infusion of a 17.5-g glutamine load. Baseline extraction by the portal-drained viscera was 7.5 +/- 1.5%; this value increased to 18 +/- 2% at 1 minute (P less than 0.01) and had returned to baseline values 60 minutes later. Arteriovenous differences were greatest across the jejunum (11.8 +/- 1.8% in the baseline period vs 33.1 +/- 3.1% at 1 minute, P less than 0.001), with smaller differences across the colon, suggesting that the jejunum was the more avid utilizer of glutamine. Glutaminase activity was 4.38 +/- 0.16 and 4.00 +/- 0.60 mumol/mg of protein/h under standard conditions in jejunal and ileal mucosa, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Hepatic glutamine metabolism and acid-base regulation.

Switching of hepatic nitrogen disposal from urea synthesis to glutamine production has been proposed as a mechanism for countering acidosis, with glutamine synthesis providing a route for the detoxification of ammonium not incorporated into urea. Isolated livers from starved rats were perfused with ammonium (0.8 mM); increasing perfusate lactate concentration 0-2 mM raised glutamine synthesis threefold whilst increasing perfusate glucose concentration 0-20 mM did not. This was true under normal and acidotic conditions. In the presence of both substrates plus either 14C-glucose or 14C-lactate, the mean specific activity of glutamine synthesised was greater for 14C-lactate. Thus, the preferred substrate for hepatic glutamine synthesis is lactate, a proton neutral reaction. Perfusion with lactate and glutamine over the pH range 6.9-7.5 with or without the glutamine synthase inhibitor L-methionine-s-sulphoxime showed that the switch in acidosis to net glutamine production is entirely due to inhibition of glutamine removal by periportal hepatocytes.

Acidosis↗
PubMed2004

Glutamine: metabolism and application in nutrition support.

Glutamine is the most abundant free amino acid in the body. It is avidly consumed by rapidly dividing cells, such as those lining the gut, because its 5-carbon skeleton can provide energy whilst the nitrogen molecules support the synthesis of nucleic acids. Patients who are maintained using conventional solutions of parenteral nutrients become depleted in glutamine, which has led to the reclassification of glutamine as a conditionally essential nutrient. Unfortunately, glutamine is unstable in solution and produces toxic byproducts on decomposition. This means that solutions of nutrients containing glutamine have a relatively short half-life, which has led to the commercialisation of stable dipeptides containing glutamine. Although it is evident that glutamine enhances nitrogen metabolism, there is a lack of consistent evidence from the initial clinical trials demonstrating that supplementation with glutamine has specific clinical advantages. The next few years will witness the performance of larger scale clinical trials and the results of these studies should define a more certain role for glutamine in routine clinical practice.

Drug Stability↗
PubMed2005

[The regulatory action of dipeptide "Deglutam" on the glutamine metabolized enzymes in the carcinosarcoma SM-1 cells].

The influence of modified antineoplaston AS2-1 (with altered ratio of L-phenylalanine and L-glutamine derivatives, "Deglutam") on the activity of glutamine synthetase, glutaminase isoforms in the carcinosarcoma SM-1, tumor weight, per cent of the inhibition of tumor growth and blood impact index was investigated in rats with carcinosarcoma SM-1. The preparation was administered in the dose of 125 mg/kg twice a day for 12 days (on the 7th day after tumor transplantation). Intensive growth of carcinosarcoma SM-1 was accompanied by activtion of the glutamine metabolizing enzymes. The dose-response effect of "Deglutam" on the studied enzymes depended on the mode of preparation administration. The intragastric administration of the preparation caused the same effect on the glutamine metabolizing of SM-1 cells; as it was earlier observed in rat liver. Administration of the modified preparation ANP AS2-1 (containing L-glutamine derivatives) influences regulation of glutamine metabolism in carcinosarcoma SM-1 cells, possibly, due to formation of substrates in the tissues of the tumor-bearing body similar to glutamine. It is also possible that in the tumor tissues these enzymes have different affinity to glutamine. This may explain greater effectiveness of the synthetic preparation on the basis of L-glutamine derivatives rather than the amino acid itself.

Animals↗
PubMed2005

Effects of glutamine in critical illness.

OBJECTIVES: Under normal physiological conditions, glutamine is synthesized in large amounts by the human body and is considered nonessential. It has been hypothesized that glutamine may become a conditionally essential amino acid in patients with catabolic disease. The objective of this study is to investigate the prognostic effect of glutamine. METHODS: For this study, we selected 48 patients from the intensive care unit. Group I consisted of 33 patients whose treatment included glutamine. We placed the remaining 15 patients in group II, and they did not receive glutamine in their treatment. We retrospectively investigated treatment time, leucocyte levels and outcome. We carried out the study between January 2002 and January 2003 in Konya Governmental Hospital, Turkey. RESULTS: The average duration of hospital stay in the glutamine group was 8 +/- 1.2 days, 58% of them leaving hospital with surrogate. However, in the group whose treatment did not include glutamine, 42% of them left the hospital surrogate, their average hospital stay being 12 +/- 3 days. In the group receiving glutamine in the treatment, there was a prominent decrease in leukocyte levels compared to the other group, and hospitalization times were shorter but there was no statistically significant difference in mortality or survival rates. CONCLUSIONS: Glutamine may decrease the catabolism. It may also have a positive effect on treatment time and the consequences of therapy in critically ill patients.

Critical Illness↗
PubMed1990

Interorgan glutamine flow regulation in metabolic acidosis.

The flow of glutamine to the kidneys is essential for generating base in response to acid loading yet neither the magnitude nor direction of this flow are normally supportive of renal ammoniagenesis. However, chronic metabolic acidosis sets in motion regulatory systems enhancing flow magnitude as well as redirecting glutamine from the splanchnic bed and ureagenesis to the kidneys for ammoniagenesis and bicarbonate generation. These mechanisms include organ-specific inductions of glutamine synthesizing and hydrolyzing enzymes at the source, muscle, and the destination, kidneys, respectively; organ-specific shifts in fluxes through competing metabolic pathways favoring glutamine formation at the expense of the ureagenic precursor alanine and unique interorgan regulation whereby upstream sites modulate subsequent downstream sites by setting the glutamine loads and the release of glutamine metabolites acting as metabolic signals. These extrarenal regulatory mechanisms act in concert making glutamine available at the expense of ureagenesis. The kidneys draw upon plasma glutamine, despite a 40% reduction in the arterial concentration, generating base in the form of renal venous bicarbonate and excreting nitrogen and protons as ammonium. Underlying this enormous renal extraction is a shift in the uptake mode from a load- to a transport-limited process closely associated with the filtered bicarbonate load. Finally the interorgan glutamine flow set in motion during acidosis can be acutely reversed, revealing a hierarchal interaction of system subserving acid base and nitrogen balance. Thus, the extraordinary responses exhibited in chronic metabolic acidosis provide a superb model for discerning regulatory systems in other physiological as well as pathophysiological conditions.

Acidosis, Renal Tubular↗
PubMed1989

Glutamine transport in isolated rabbit ileal epithelium.

Oral rehydration therapy of diarrhea is based upon the promoting effect of glucose on sodium absorption. This ionic transport could be further enhanced by the addition of glutamine, an amino acid which is also the major energy source for the enterocyte. The aim of this in vitro study was to assess glutamine intestinal transport and to evaluate ionic movements associated with this transport. Strips of ileal epithelium from rabbits at weaning were mounted in Ussing chambers. Both sides of the epithelium were bathed with Ringer solution supplemented, after a basal period, with 2, 5, 10 or 25 mM glutamine. Unidirectional transepithelial fluxes of glutamine were measured with 3H and 14C tracers. Short circuit current, reflecting ionic transport, and potential difference were continuously monitored. Glucose 9 mM was later added to both sides. An apparent bidirectionnal transepithelial transport of glutamine was observed. The net result was a dose-dependent absorption (1.8 +/- 0.3 mumoles/h. cm2 at 25 mM). Glutamine induced a significant (p less than 0.01) dose-dependent saturable increase of short-circuit current and potential difference; the epithelial conductance was not modified. The addition of glucose did not significantly modify glutamine transport but caused and additional increase of short-circuit current. These results suggest that glutamine is actively transported by the ileal epithelium and stimulates ionic transport, suggesting Na+ absorption. The mechanism of this stimulation may differ from that of glucose, as the effects were additive. The present data provide support to the clinical evaluation of glutamine-supplemented rehydration solutions in the treatment of diarrhea.

Animals↗
PubMed1986

[Study on placental L-glutamine transport mechanism using microvilli vesicles].

Using microvillous (brush border) membrane vesicles prepared from human term placenta, the uptake of L-glutamine was studied using a rapid filtration technique. The uptake of L-glutamine into the vesicles was osmotically sensitive. A Na+ electrochemical gradient (extravesicular greater than intravesicular) stimulated the initial rate of L-glutamine uptake and the Na+ dependent uptake of L-glutamine into vesicles showed a typical overshoot phenomenon. This overshoot and the initial rate of uptake were markedly increased when the intravesicular space was rendered electrically more negative by membrane diffusion potentials, induced by the use of highly permeant anions. A similar stimulation of L-glutamine uptake was observed when membrane potential (inside negative) was imposed by K+ diffusion potentials via valinomycin. These results indicated that a sodium dependent uptake of L-glutamine into the microvillous membrane vesicles was dependent on the electrical potential difference of membrane. The initial rate of L-glutamine transport exhibited saturation kinetics with respect to L-glutamine concentration; the apparent Km of 0.42 mM and Vmax of 1.54 nmol/mg protein/20 sec were calculated. The uptake of L-glutamine into the vesicles was competitively inhibited by L-alanine.

Amino Acids↗
PubMed1986

Glutamine metabolism in rat hepatocytes. Stimulation by a nonmetabolizable analog of leucine.

The metabolic effects of beta-(+/-)-2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid (BCH), a nonmetabolizable analog of leucine and known activator of glutamate dehydrogenase, were studied in hepatocytes isolated from fed and fasted rats. With glutamine as substrate, BCH stimulated in a concentration-dependent manner urea synthesis in both physiological states and glucose formation in hepatocytes from fasted rats. Despite the much higher rates of ureagenesis in the fasted animals, the degree of stimulation by BCH, over 2-fold, was similar. The effect of the drug was specific for glutamine since the rates of urea synthesis from NH4Cl, alanine, and asparagine were essentially unaltered. The stimulation of glutamine catabolism by BCH led to a decrease in the content of intracellular glutamine. The redox states of the mitochondrial and cytosolic nicotinamide adenine dinucleotides remained unaltered. In hepatocytes isolated from fasted rats and incubated with 5 mM glutamine the BCH-induced increases in urea, ammonia, and the amino acids, glutamate, aspartate, and alanine, accounted fully for the 2.4-fold rise in glutamine utilization. The stimulatory effects of BCH and glucagon on the formation of glucose, urea, and 14CO2 from [U-14C]glutamine were additive. Aminooxyacetate, and inhibitor of transaminases, neither blocked glutamine catabolism (as measured by the sum of urea, ammonia, and glutamate) nor prevented its activation by BCH. It is suggested that, in isolated hepatocytes, BCH-induced stimulation of glucose and urea formation from glutamine results from activation of glutaminase by a mechanism which is distinct from that of glucagon.

3-Hydroxybutyric Acid↗
PubMed1993

Glutamine is essential for epidermal growth factor-stimulated intestinal cell proliferation.

BACKGROUND: Glutamine stimulates growth of intestinal mucosa in vivo, but the mechanisms involved are unknown. The purpose of this study was to determine whether glutamine is essential for proliferation of enterocytes stimulated by epidermal growth factor (EGF). In addition, we determined which specific mitogenic actions of EGF require glutamine. METHODS: A nontransformed rat intestinal mucosal cell line (IEC-6) was stimulated with EGF (20 ng/ml) without and with glutamine (0.1 to 10 mmol/L). DNA, RNA, and protein synthesis were quantitated by determining incorporation of tritiated thymidine, tritiated uridine, and 14C-leucine, respectively. Cell numbers and messenger RNA levels of early growth response genes (zif268, jun-B, c-myc) were also determined. RESULTS: Glutamine was required for EGF stimulation of DNA, RNA, and protein synthesis and cell replication; however, EGF-stimulated expression of zif268, jun-B, and c-myc occurred in the absence of glutamine. CONCLUSIONS: This study showed that glutamine is essential for EGF-stimulated intestinal mucosal cell proliferation. The mitogenic effects of EGF can be divided into the glutamine-independent, such as the signal transduction pathway leading to the induction of early growth response genes, and the glutamine-dependent, including DNA, RNA, and protein synthesis.

Animals↗
PubMed1985

Purification and regulation of glutamine synthetase in a collagenolytic Vibrio alginolyticus strain.

Glutamine synthetase (EC 6.3.1.2) has been purified from a collagenolytic Vibrio alginolyticus strain. The apparent molecular weight of the glutamine synthetase subunit was approximately 62,000. This indicates a particle weight for the undissociated enzyme of 744,000, assuming the enzyme is the typical dodecamer. The glutamine synthetase enzyme had a sedimentation coefficient of 25.9 S and seems to be regulated by adenylylation and deadenylylation. The pH profiles assayed by the gamma-glutamyltransferase method were similar for NH4-shocked and unshocked cell extracts and isoactivity point was not obtained from these curves. The optimum pH for purified and crude cell extracts was 7.9. Cell-free glutamine synthetase was inhibited by some amino acids and AMP. The transferase activity of glutamine synthetase from mid-exponential phase cells varied greatly depending on the sources of nitrogen or carbon in the growth medium. Glutamine synthetase level was regulated by nitrogen catabolite repression by (NH4)2SO4 and glutamine, but cells grown in the presence of proline, leucine, isoleucine, tryptophan, histidine, glutamic acid, glycine and arginine had enhanced levels of transferase activity. Glutamine synthetase was not subject to glucose, sucrose, fructose, glycerol or maltose catabolite repression and these sugars had the opposite effect and markedly enhanced glutamine synthetase activity.

Ammonium Sulfate↗