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)

Flux through the tricarboxylic acid cycle was calculated from oxygen consumption in hearts perfused near the physiological work load. Activities of citrate synthase, 2-oxoglutarate dehydrogenase and succinate dehydrogenase were measured in the same hearts. Only the activities of 2-oxoglutarate dehydrogenase correlated with calculated fluxes through the cycle.
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PMID:Tricarboxylic acid cycle flux and enzyme activities in the isolated working rat heart. 734 78

The effects of chronic iron deficiency anemia on brain (cortex) metabolism were estimated by 31P-nuclear magnetic resonance spectroscopy and biochemical analyses in male Wistar rats. Iron deficiency anemia was induced by supplying diet containing either approximately 2 or approximately 6 ppm Fe. Control diet was supplemented with 100 ppm Fe as ferric citrate. After 8-9 weeks, blood hemoglobin levels were approximately 13, 5, and 3 g/100 ml in the 100 ppm, 6 ppm, and 2 ppm Fe group, respectively. The blood lactate levels at rest in these groups were approximately 3, 5, and 6 mM. The blood glucose concentration also tended to be elevated in iron-deficient rats. The high-energy phosphate contents in brain were not affected by iron deficiency. The activities of succinate dehydrogenase and cytochrome oxidase per unit protein in the 2 ppm Fe group were significantly less than in the 100 ppm Fe group, but those activities were not significantly affected by feeding diet with 6 ppm Fe. The activities of lactate dehydrogenase in iron-deficient group tended to be elevated but not significantly. The activities of non-iron containing mitochondrial enzymes, citrate synthase and beta-hydroxyacyl CoA dehydrogenase, were unchanged. It is suggested that the brain has a higher tolerance to iron deficiency than skeletal muscle in terms of the metabolic characteristics, although this may be associated with a lower level of neural activity.
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PMID:Effects of chronic iron deficiency anemia on brain metabolism. 756 62

Muscle carnitine levels were examined in 31 younger [mean (SD), 27 (5) years] and 27 older [49 (8) years] men. Needle biopsies were obtained from the lateral gastrocnemius or vastus lateralis muscles and assayed for free and total carnitine concentrations via a 5,5'-Dithiobis-(2-nitrobenzoic acid) DTNB-linked spectrophotometric procedure. A subgroup of subjects (n = 28) were assessed for citrate synthase (CS) and succinate dehydrogenase (SDH) activity, and type I muscle fiber composition (% type I fibers). An additional sub-group of nine subjects was assessed for free and total serum carnitine levels. No mean (SEM) differences in free [21.6 (0.7) vs 20.3 (0.9) mumol.g dry weight-1] and total [26.4 (0.6) vs 26.1 (0.9) mumol.g dry weight-1) muscle carnitine levels were found between the younger and older subjects, respectively. Correlational data revealed no significant relationships between total muscle carnitine and CS (r = -0.36), SDH (r = -0.26), or % type I fibers (r = -0.16). In addition, there was a low non-significant relationship between serum and muscle total carnitine concentrations (r = -0.44). These findings suggest that muscle carnitine levels are similar between younger and older males, and there does not appear to be any relationship between muscle carnitine and markers of muscle oxidative potential (i.e., oxidative enzymes, % type I fiber). Since serum carnitine is often used as an indicator of body carnitine status, it is noteworthy that we found a low negative relationship between blood and muscle carnitine concentrations.
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PMID:Relationships between muscle carnitine, age and oxidative status. 758 81

We have identified and sequenced four genes that encode the protein subunits comprising the succinate dehydrogenase enzyme complex (Sdh) of the rickettsia Coxiella burnetii. The Sdh-encoding gene cluster (sdhCDAB) begins 3326 bp upstream from the citrate synthase-encoding gene (gltA) start codon and is read with opposite polarity. An open reading frame encoding the N-terminal 280 amino acids (aa) of 2-oxoglutarate dehydrogenase (SucA) begins 24 bp downstream from the stop codon of the gene specifying the iron-sulfur subunit (sdhB) of Sdh. The deduced aa sequence of Sdh subunits and the N-terminal portion of SucA revealed significant aa identity with the Esherichia coli homologues ranging from a low of 36.6% for SdhD to a high of 61.2% for SdhA and SdhB. Primer extension identified transcription start points (tsp) for sdh and sucA. The region upstream from the sdh tsp, but not the sucA tsp, displayed homology to promoter consensus sequences of E. coli. Further evidence that sucA transcription can occur independent of sdh transcription was provided by demonstrating that a TnphoA insertion disrupting sdhB had no effect on the production of SucA by an E. coli cell-extract-directed in vitro transcription/translation system. The plasmid clone pLPM60, which carries the C. burnetii sdhCDAB coding and upstream regulatory regions, rescued an E. coli sdhA mutant (MOB252), indicating functional expression of the rickettsial locus. A cell extract of MOB252 transformed with pLPM60 showed a sixfold greater level of Sdh enzyme activity over the E. coli wild type. A plasmid clone lacking the sdh upstream regulatory region did not complement nor produce sdh mRNA by dot blot analysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of the succinate dehydrogenase-encoding gene cluster (sdh) from the rickettsia Coxiella burnetii. 769 64

We studied the tumor host response to excessive doses of an anabolic steroid (nandrolone propionate, 2.5 mg 20 g intraperitoneally every second day for 11 days) with respect to body composition and tumor cell kinetics in MCG 101 sarcoma-bearing mice (C57BL/6J) with progressive cachexia. Although survival and food intake were not affected, a significant weight gain was observed that was essentially attributed to water retention. Net protein content was increased only to a minor extent (15%), of which only the liver accounted for a significant part of the body compartments. Hepatic protein accumulation was obviously caused by decreased protein degradation, since hepatic RNA content was unchanged. After anabolic steroid administration, reduced histochemical staining of succinate dehydrogenase was observed in skeletal muscles rich in oxidative type 1 fibers, but it was not different from that of tumor-bearing control animals, which was also confirmed by measurements of citrate synthase and cytochrome c oxidase activities in skeletal muscle and liver tissue. The anabolic steroid had no significant effect on tumor growth in terms of weight progression, energy state, polyamine synthesis rate, cell division rate, and cell cycle cytocompartments. We conclude that anabolic steroid supplementation is not therapeutically beneficial in counteracting progressive weight loss in experimental cancer.
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PMID:Effects of nandrolone propionate on experimental tumor growth and cancer cachexia. 772 66

A comparative study was carried out on the glucose metabolism in Babesia microti (BM) and Babesia rodhaini (BR) by analyzing the enzyme activities. The lactate dehydrogenase (LDH) activity in BM showed significantly lower values than that in BR, whereas citrate synthase (CS) and malate dehydrogenase (MDH) activities were remarkably higher in BM. In addition, pyruvate dehydrogenase (PDH), isocitrate dehydrogenase (ICDH), alpha-ketoglutarate dehydrogenase (KGDH), and succinate dehydrogenase (SDH) activities also tended to be higher in BM. Then, the change of enzyme activities related to the proliferation of parasites was examined. In BM infected mice, the parasitemia increased from day 15 to day 19 after inoculation (a.i.). While BM showed decrease of G6PD and LDH activities at day 19 a.i., it showed remarkably increased activities in CS and MDH (368 and 8,842 nmol/min.mg protein, respectively). In addition, PDH, ICDH, KGDH, and SDH activities also tended to increase from day 15 to 19 a.i. In BR infected mice, parasitemia increased from day 9 to day 12 a.i. LDH activity showed a considerable increase at day 12 a.i. (12,920 IU/mg.protein). Although CS and MDH activities also showed a slight increase at day 12 a.i., the activities of PDH, ICDH, KGDH and SDH didn't change from day 9 to 12 a.i. Since these changes observed in the enzyme activities of BM and BR seemed to be correlated with their proliferation, it was suggested that BM and BR depended on aerobic and anaerobic pathways, respectively, for their glucose metabolism.
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PMID:Enzyme activities related to glucose metabolism in Babesia microti and Babesia rodhaini. 775 34

The postnatal development of the complexes of the electron transport chain in isolated rat brain mitochondria were investigated. Nonsynaptosomal brain mitochondria were isolated from rats aged 1-60 days, and the activities of mitochondrial complexes I, II-III, IV, V and citrate synthase were measured. There was a significant increase in the activity of complex I from postnatal day 1 to day 21, and in the activities of complex II-III, complex IV and citrate synthase from postnatal day 1 to day 60. In contrast, the activity of complex V increased significantly between postnatal day 1 and day 10 where it attained adult levels. These data are consistent with the increasing demand for mitochondrial ATP production as the brain develops and as aerobic glycolysis becomes the major pathway for energy production.
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PMID:Postnatal development of the complexes of the electron transport chain in isolated rat brain mitochondria. 776 12

The purpose of this investigation was to examine the histochemical and enzymatic characteristics of skeletal muscle after 20 yr of distance running training. Twenty-eight men were first studied between 1966 and 1974 when they were all highly trained distance runners. On the basis of their training regimens in the interim between testing, subjects were described as highly trained (HI; n = 11), fitness trained (FIT; n = 10), or untrained (UT; n = 7). Gastrocnemius muscle biopsy samples revealed a mean increase (P < 0.05) in the proportion of type I fibers of the FIT and UT groups, whereas the HI group, which was initially characterized by a high percentage (> 70%) of type I fibers, was unchanged. Although the mean fiber type change of the HI group was similar between evaluations, 6 of the 11 subjects did elicit an increase in the percentage of type I fibers. A subgroup of elite distance runners who had continued to train for competition experienced an approximately 25% reduction (P > 0.05) in muscle succinate dehydrogenase activity and decreases (P > 0.05) in types I and II muscle fiber areas. On the average, in 1993 the HI group had higher (P < 0.05) succinate dehydrogenase and citrate synthase activities than the FIT and UT groups, whereas phosphorylase activity did not differ among the three groups. These data suggest that the middle-aged men in this study had a significantly greater proportion of type I muscle fibers than when they were 20 yr younger.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Skeletal muscle characteristics among distance runners: a 20-yr follow-up study. 777 25

L-3,4-Dihydroxyphenylalanine (L-dopa) is toxic for human neuroblastoma cells NB69 and its toxicity is related to several mechanisms including quinone formation and enhanced production of free radicals related to the metabolism of dopamine via monoamine oxidase type B. We studied the effect of L-DOPA on activities of enzyme complexes in the electron transport chain (ETC) in homogenate preparations from the human neuroblastoma cell line NB69. As a preliminary step we compared the activity of ETC in cellular homogenates with that of purified mitochondria from NB69 cells and rat brain. Specific activities for complex I, complex II-III, and complex IV in NB69 cells were, respectively, 65, 96, and 32% of those in brain mitochondria. Complex I activity was inhibited in a dose-dependent way by 1-methyl-4-phenylpyridinium ion with an EC50 of approximately 150 microM. Treatment with 0.25 mM L-dopa for 5 days reduces complex IV activity to 74% of control values but does not change either complex I or citrate synthase. Ascorbic acid (1 mM), which protects NB69 cells from L-dopa-induced neurotoxicity, increases complex IV activity to 133% of the control and does not change other ETC complexes. Ascorbic acid also reverses L-dopa-induced reduction of complex IV activity in NB69 cells. This observation might indicate that the protection observed with ascorbic acid is related to complex IV activation. In vitro incubation with L-dopa (0.125-4 mM) for 2 min produced a dose-dependent reduction of complex IV without change in complex I and II-III activities.
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PMID:L-dopa inhibits complex IV of the electron transport chain in catecholamine-rich human neuroblastoma NB69 cells. 783 50

The effects of long-term, moderate physical exercise on in vivo glucose uptake, levels of two glucose transporter proteins (GLUT1 and GLUT4) and activities of various key enzymes of energy metabolism were measured in skeletal muscle from streptozotocin-diabetic rats. Diabetes (12-16 weeks) reduced the in vivo glucose uptake (glucose metabolic index, GMI) in muscle containing mainly type I fibres by 55% but had no effect in muscles containing mainly type IIa and IIb fibres. GMI was increased in the diabetic white skeletal muscle (mainly type IIb fibres) by more than 120%. In contrast to the complex changes in GMI, GLUT4 levels were reduced in all types of skeletal muscle from diabetic rats with no change in GLUT1 levels. Exercise training had no effects on GMI or the glucose transporter levels. Streptozotocin induced diabetes significantly reduced the oxidative capacity of skeletal muscle assayed as the activities of citrate synthase, succinate dehydrogenase and cytochrome c oxidase. Training increased the activities of oxidative enzymes, with this increase being more prominent in the diabetic animals. The present data indicate that long-term streptozotocin-induced diabetes decreases oxidative metabolic capacity and GLUT4 protein levels in skeletal muscle, but that the changes of glucose transport largely depend on the fibre type composition. Moderate training fully reverses the effect of insulinopenia and hyperglycaemia on muscle oxidative metabolism. In contrast to the previous suggestions, the expression of GLUT4 is not correlated with the capacity of oxidative metabolism in skeletal muscle of streptozotocin-diabetic rats.
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PMID:Dissociation of the effects of training on oxidative metabolism, glucose utilisation and GLUT4 levels in skeletal muscle of streptozotocin-diabetic rats. 797 Nov 42


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