Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study the effects of insulin, glucocorticoids and thyroid hormones on macrophage metabolism and function were investigated. The maximum activities of hexokinase, glucose-6-phosphate dehydrogenase, glutaminase and citrate synthase were determined in macrophages obtained from hormone-treated rats and those cultured for a period of 48 h in the presence of hormones. Macrophage phagocytosis was markedly inhibited by dexamethasone and thyroid hormones, remaining unchanged when insulin was added to the culture medium, however. The changes in the enzyme activities caused by hormone treatments of the rats were very similar to those found in culture. Insulin enhanced citrate synthase and hexokinase activities and diminished those of glutaminase and glucose-6-phosphate dehydrogenase. Dexamethasone had a similar effect except on glucose-6-phosphate dehydrogenase. The addition of thyroid hormones to the culture medium raised the activities of glutaminase and hexokinase and reduced that of citrate synthase. The results presented support the suggestion that the effects of insulin, glucocorticoids and thyroid hormones on immune and inflammatory responses could well be mediated through changes in macrophage metabolism.
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PMID:Effects of insulin, glucocorticoids and thyroid hormones on the activities of key enzymes of glycolysis, glutaminolysis, the pentose-phosphate pathway and the Krebs cycle in rat macrophages. 147 28

Previous reports from our laboratory showed that rats fed a polyunsaturated fatty acid-rich diet (UC), during an acute intervals, present important changes in macrophage metabolism and function, while a saturated fatty acid diet (SC) did not induce significant changes (10). In this study, two important questions were addressed: 1. the persistence of the changes induced by the UC and 2. the effect of a SC offered during ageing. The maximal activities of hexokinase, glucose-6-phosphate dehydrogenase, glutaminase, citrate synthase and glutathione peroxidase and the total content of lipid peroxides were measured in resident and inflammatory macrophages of rats fed control chow (CC), UC or SC during 14 months. Intraperitoneal cell migration by thioglycollate injection and the phagocytosis capacity were also evaluated. The results indicate that: 1) the changes caused by UC are exacerbated during ageing, and 2) the SC, given during a prolonged period of time, also caused important alterations of macrophage metabolism and function.
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PMID:Metabolic and functional changes in macrophages of rats fed polyunsaturated or saturated fatty acid rich-diets during ageing. 162 81

We studied mechanism(s) by which adaptations of renal TCA cycle metabolism abet ammoniagenesis from glutamine in altered acid-base states. Renal tubules from control, acidotic, or alkalotic rats were incubated at pH 7.4 with 1 mM [3-13C,5-15N]glutamine or 2 mM [3-13C]pyruvate. In acidosis there was a significantly higher flux through glutaminase and through glutamate, 2-oxoglutarate, succinate and malate dehydrogenases as well as markedly enhanced 13C-glucose formation. Alkalosis was associated with little change in 13C flux from glutamine to TCA cycle intermediates compared with control but production of 15NH3 and 13C glucose was significantly diminished. The current studies indicate that renal ammoniagenesis might be regulated at the sites of citrate synthetase (CS) and/or alpha-ketoglutarate dehydrogenase (KGDH). Thus, in chronic metabolic acidosis decreased flux through CS and increased flux through KGDH resulted in enhanced flux through glutamate dehydrogenase and glutaminase pathway. The opposite occurred in alkalosis. The data suggest that in various acid-base states the rate of renal gluconeogenesis is linearly correlated with malate efflux from the mitochondria. In renal tissue, inhibition occurs at one site of the TCA cycle there is an augmentation of fluxes through pathways beyond that site in order to maintain the respiratory process and the redox state in the mitochondria.
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PMID:Adaptation of renal tricarboxylic acid cycle metabolism to various acid-base states: study with [3-13C,5-15N]glutamine. 177 Sep 13

1. Cells from the bone marrow and cells from the thymus of the rat were incubated in the presence of glucose and glutamine and phytohaemagglutinin, concanavalin-A or lipopolysaccharide. Cells were harvested at times up to 4 hr, extracted and maximum activities of hexokinase, lactate dehydrogenase, citrate synthase or glutaminase measured. 2. In bone marrow cells, there were little changes in enzyme activities except for an increase in the activity of citrate synthase which was prevented by concanavalin-A. This mitogen also caused a decrease in the activity of hexokinase. 3. In contrast, in thymocytes, the activities of hexokinase and glutaminase were decreased in the control condition but addition of lipopolysaccharide, a B-cell mitogen prevented these decreases in activity and concanavalin-A maintained the activity of glutaminase. Concanavalin-A caused a decrease in hexokinase activity but a marked increase in that of glutaminase. 4. It is suggested that changes in the maximum activities of hexokinase and glutaminase over this 4 hr period may represent the effect of removal of thymus-produced growth factors, whose effects can be replaced, at least in part, by two mitogens.
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PMID:Effect of B- and T-cell mitogens on the maximum activities of hexokinase, lactate dehydrogenase, citrate synthase and glutaminase in bone marrow cells and thymocytes of the rat during four hours of culture. 177 87

1. The maximal activities of hexokinase (HK), 6-phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and glutaminase (GLU) which provide a quantitative indices of flux through several important pathways have been measured in the skin of haired Balb/c and hairless Balb/c (nu/nu) mice under normal and dietary stress. 2. The skin of old haired mice exhibited higher PFK and LDH activities with lower HK, CS and GLU activities. All activities of enzymes associated with energy metabolism in the skin of old hairless mice were higher than those in the skin of haired mice. 3. HK, LDH, CS and GLU activities were maintained at normal levels in the skin of haired mice when these mice were fed diets deficient in energy or protein components (HPLE, LPNE). These enzymes however were severely suppressed when mice were fed a diet deficient in both energy and protein components (LPLE). Recovery of activities of these enzymes to the control level was observed when mice were refed with the normal diet for a week.
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PMID:The effects of diet on the maximal activities of glutaminase, citrate synthase, hexokinase, 6-phosphofructokinase and lactate dehydrogenase in the skin of haired and hairless mice of various ages. 182 43

1. The maximal activities of hexokinase (HK), 6-phosphofructokinase (PFK), lactate dehydrogenase, citrate synthase (CS) and glutaminase (GLU) which provide quantitative and qualitative indices of flux through several important metabolic pathways have been examined in the wounded skin of haired immune competent Balb/c mice and hairless immune deficient Balb/c (nu/nu) mice of various ages during the first ten days of wound healing. 2. The potential for glucose utilization and for aerobic metabolism as suggested by the maximal activities of HK, PFK, CS, were raised in the skin of Balb/c mice of various ages on all post wounding days. Increases in the maximal activity of GLU was observed only in the skin of 6 and 10 weeks old Balb/c mice during wound healing. 3. There was no evidence of a contribution to the maximal activity of GLU by infiltrating cells of the immune system to the wound site in the skin of either haired or hairless mice.
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PMID:Maximal activities of glutaminase, citrate synthase, hexokinase, 6-phosphofructokinase and lactate dehydrogenase in skin of immune-competent Balb/c and immune-deficient Balb/c (nu/nu) mice during wound healing. 182 91

It has been widely reported that polyunsaturated fatty acids (PU-FA n-6) in the diet lead to immunosuppression. In the present study, the activity of key enzymes several metabolic pathways were measured in the immune tissues of rats fed polyunsaturated (UC) or saturated fatty (SC) acids-rich diets. The following enzyme activities were measured: hexokinase, citrate synthase, glucose-6-phosphate dehydrogenase, glutaminase and malic enzyme. The metabolism of immune tissues was markedly changed by the fat content of the diet. However, UC diet determined more significant metabolic changes than SC diet.
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PMID:Polyunsaturated and saturated fatty acids-rich diets and immune tissues. 2. Maximal activities of key enzymes of glutaminolysis, glycolysis, pentose-phosphate-pathway and Krebs cycle in thymus, spleen and mesenteric lymph nodes. 209 Jan 3

1. Maximal activities of some key enzymes of glycolysis, the pentose phosphate pathway, the tricarboxylic acid cycle and glutaminolysis were measured in homogenates from a variety of normal, neoplastic and suppressed cells. 2. The relative activities of hexokinase and 6-phosphofructokinase suggest that, particularly in neoplastic cells, in which the capacity for glucose transport is high, hexokinase could approach saturation in respect to intracellular glucose; consequently, hexokinase and phosphofructokinase could play an important role in the regulation of glycolytic flux in these cells. 3. The activity of pyruvate kinase is considerably higher in tumorigenic cells than in non-tumorigenic cells and higher in metastatic cells than in tumorigenic cells: for non-tumorigenic cells the activities range from 28.4 to 574, for tumorigenic cells from 899 to 1280, and for metastatic cells from 1590 to 1627 nmol/min per mg of protein. 4. The ratio of pyruvate kinase activity to 2 x phosphofructokinase activity is very high in neoplastic cells. The mean is 22.4 for neoplastic cells, whereas for muscle from 60 different animals it is only 3.8. 5. Both citrate synthase and isocitrate dehydrogenase activities are present in non-neoplastic and neoplastic cells, suggesting that the full complement of tricarboxylic-acid-cycle enzymes are present in these latter cells. 6. In neoplastic cells, the activity of glutaminase is similar to or greater than that of hexokinase, which suggests that glutamine may be as important as glucose for energy generation in these cells.
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PMID:Maximum activities of key enzymes of glycolysis, glutaminolysis, pentose phosphate pathway and tricarboxylic acid cycle in normal, neoplastic and suppressed cells. 230 81

1. The activities of hexokinase, lactate dehydrogenase and citrate synthase were maintained in mesenteric lymph node lymphocytes during 4 hr of culture: the activity of glutaminase increased during this period of time. 2. In splenocytes, the activity of hexokinase decreased markedly during the 4 hr period, whereas those of lactate dehydrogenase and glutaminase remained constant, and that of citrate synthase increased dramatically. 3. In both mesenteric lymphocytes and splenocytes, addition of the T-cell mitogens, phytohaemagglutinin or concanavalin-A, to the culture medium caused decreases in the activities of both hexokinase and citrate synthase. 4. In contrast, these mitogens increased the activity of glutaminase in both cell types. 5. Addition of the B-cell mitogen, bacterial lipopolysaccharide, had little effect on hexokinase, lactate dehydrogenase or citrate synthase but increased markedly that of glutaminase in mesenteric lymph node lymphocytes. 6. In splenocytes this mitogen prevented much of the decrease in hexokinase activity, increased the activities of citrate synthase and glutaminase but had little effect on that of lactate dehydrogenase.
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PMID:Effect of mitogens on the maximum activities of hexokinase, lactate dehydrogenase, citrate synthase and glutaminase in rat mesenteric lymph node lymphocytes and splenocytes during the early period of culture. 233 97

1. The effect of dexamethasone (30 micrograms day-1 100 g-1 body wt.) on the metabolism of glucose and glutamine was studied in the small intestine of rats after 9 days of treatment. 2. Dexamethasone treatment resulted in negative nitrogen balance (P less than 0.001), and produced increases in the concentrations of plasma glucose (22%, P less than 0.05), alanine (32%, P less than 0.001) and insulin (127%, P less than 0.001), but a decrease in the plasma concentration of glutamine (20%, P less than 0.05). 3. Portal-drained visceral blood flow increased by approximately 22% (P less than 0.001) in dexamethasone-treated rats, and was accompanied by a decrease in the arterio-venous concentration difference of glucose (43%, P less than 0.001) and an increase in that of lactate (22%, P less than 0.05), glutamine (35%, P less than 0.01), glutamate (33%, P less than 0.01) and alanine (21%, P less than 0.05). 4. Enterocytes isolated from dexamethasone-treated rats showed decreased and increased rates of glucose and glutamine utilization, respectively. 5. The maximal activities of hexokinase, 6-phosphofructokinase, citrate synthase and oxoglutarate dehydrogenase were decreased (30-64%, P less than 0.001) in intestinal mucosal scrapings of dexamethasone-treated rats, whereas the activity of glutaminase was increased (35%, P less than 0.001). 6. It is concluded that glucocorticoid administration decreases the rate of glucose utilization but increases that of glutamine (both in vivo and in vitro) by the epithelial cells of the small intestine. This may be caused by changes in the maximal activities of key enzymes in the pathways of glucose and glutamine metabolism in these cells.
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PMID:Effect of glucocorticoid treatment on glucose and glutamine metabolism by the small intestine of the rat. 340 28


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