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)

The condensation of two propionyl-CoA units or a propionyl-CoA with acetyl-CoA is required for the synthesis of 2-methylvalerate or 2-methylbutyrate, respectively, two of the major fermentation products of Ascaris anaerobic muscle metabolism. An enzyme that preferentially catalyzes the condensation of propionyl-CoA rather than acetyl-CoA has been purified from the mitochondria of the parasitic intestinal nematode Ascaris lumbricoides var. suum. The purified enzyme is over 10 times more active with propionyl-CoA than with acetyl-CoA as substrate. It also catalyzes the coenzyme A-dependent hydrolysis of acetoacetyl-CoA at a rate four times higher than the propionyl-CoA condensation reaction. The purified Ascaris condensing enzyme preferentially forms the 2-methyl-branched-chain keto acids rather than the corresponding straight chain compounds. The native molecular weight of the purified enzyme was estimated to be 160,000 by gel filtration chromatography and 158,000 by high pressure liquid chromatography. The enzyme migrated as a single protein band with Mr 40,000 during sodium dodecyl sulfate-polyacrylamide electrophoresis, indicating that the enzyme is composed of four subunits of the same molecular weight. Chromatography on CM-sephadex resulted in the isolation of two separate peaks of activity, designated as A and B. Both A and B had the same molecular weight and subunit composition. However, they differed in their specific activities and isoelectric points. The pIs of condensing enzymes A and B were 7.6 and 8.4, respectively. Propionyl-CoA was the best substrate for the condensation reaction with both enzymes. However, the specific activity of enzyme B for both propionyl-CoA condensation (3.4 mumol/min/mg protein) and acetoacetyl-CoA thiolysis (13.8 mumol/min/mg protein) was 2.4 times higher than that obtained with enzyme A. Similarly, chromatography on phosphocellulose resolved the Ascaris condensing enzyme activity into one minor and two major peaks. All of these components had the same molecular weight and subunit composition, but differed in their specific activities. The two major phosphocellulose peaks cross-reacted immunologically when examined by the Ouchterlony double immunodiffusion technique. In addition, antiserum against the phosphocellulose most active form cross-reacted with forms A and B isolated by chromatography of the enzyme on CM-Sephadex, indicating that all forms were immunochemically related.
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PMID:Propionyl-CoA condensing enzyme from Ascaris muscle mitochondria. I. Isolation and characterization of multiple forms. 199 Sep 76

Gill cell suspensions from freshwater (FW)- and seawater (SW)-adapted teleosts were obtained by density gradient centrifugation. The proportion of chloride cells (CCs) in the mixed cell suspensions was estimated using the fluorescent mitochondrial stain, DASPMEI, and ranged from less than 1% (FW-adapted tilapia) to approximately 13% (SW-adapted toadfish). The gill cells displayed relatively high viability based on Trypan Blue exclusion (greater than 75%), lactate dehydrogenase leakage (less than 6.5% h-1), oxygen consumption rates (5-15 mumol g-1 cell wet mass h-1) and ATP levels (1-3 mumol g-1 cell wet mass). There were no obvious differences between the viability of CCs and the other cell types present. An initial comparison of gill oxidative metabolism in SW-adapted tilapia (Oreochromis mossambicus) and toadfish (Opsanus beta) demonstrated that both species oxidized glucose and lactate at substantially greater rates than alanine or oleate. Metabolic rates were significantly higher in toadfish cell suspensions. Kinetic experiments revealed that toadfish gill cells displayed lower values of Km and higher values of Vm for both lactate and glucose, in comparison to tilapia. The elevated metabolism in toadfish gill cells was correlated with increased activities of the oxidative enzyme citrate synthase and Na+/K+-ATPase. The toadfish cell suspensions had a greater proportion of CCs and it is likely that the difference in CC numbers between the two species is the basis for the observed differences in enzyme activities and rates of oxidative metabolism. This idea is supported by the highly significant correlation between Na+/K+-ATPase activity (or CC numbers) and rates of lactate oxidation in gill cell suspensions from FW- and SW-adapted tilapia and toadfish, as well as SW-adapted tilapia chronically treated with cortisol to elevate CC numbers. Although it has been assumed widely that the high metabolic rate of gill tissue reflects, in part, the oxidative demands of the chloride cell, the results of this study provide the first experimental, albeit indirect, evidence for differential rates of metabolism in the various cell types that comprise the gill.
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PMID:Metabolism of isolated fish gill cells: contribution of epithelial chloride cells. 254 65

When temperature differences are taken into account, turtle brains use glucose at one-sixth the rate reported in rat brains. Na+-K+-ATPase activities are 2- to 2.5-fold higher in rat than in turtle brains. Maximal activities of hexokinase and lactate dehydrogenase are similar, whereas citrate synthase activities are two- to threefold higher in rat than turtle brains at the respective biological temperatures. Voltage-dependent Ca2+ channel densities, when compared between the two species, showed no consistent pattern. These data, along with the threefold differences in density of voltage-dependent Na+ channels reported by Lutz et al., are consistent with the idea that lower rates of channel and pump-mediated Na+ and K+ fluxes result in lower rates of aerobic energy metabolism in turtle brains compared with rat brains.
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PMID:Turtles and rats: a biochemical comparison of anoxia-tolerant and anoxia-sensitive brains. 255 54

To explore the possibility of liver enzyme induction by deltamethrin, subacute intoxication was carried out in rats for 28 days, by administration 7.2 mg.Kg-1.day-1 of deltamethrin i.p. delivered by an osmotic pump inserted in the peritoneal cavity. The body weight curve of the treated rats increased slightly but not significantly compared to the controls. No neurotoxic effect was observed. Blood parameters were unchanged, except for eosinophilia and an increase in the plasma Na+ level. Cytochrome P-450, cytochrome b5, NADPH-cytochrome c reductase, esterases and the activities of six mixed function oxidases were assayed. No variation was noted. Ultrastructural study of the liver, more specially in midlobular region, showed that deltamethrin increased the number of mitochondria and altered their shape which became irregular. These findings were consistent with morphometric results. Succinate cytochrome c reductase, citrate synthase and cytochrome c oxidase were essayed, only this last showed a significant enhancement in deltamethrin treated rats.
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PMID:Effects on rats of subacute intoxication with deltamethrin via an osmotic pump. 263 42

ATP:citrate lyase [ATP citrate (pro-3S)-lyase; EC 4.1.3.8] was purified and characterized from the cells of Hydrogenobacter thermophilus, an aerobic, thermophilic, hydrogen-oxidizing bacterium which fixes carbon dioxide by a reductive carboxylic acid cycle. The enzyme was quite stable, even in the absence of sulfhydryl reagents. Optimum pH for reaction was 6.7 to 6.9, and optimum temperature was around 80 degrees C. The molecular weight of native enzyme was estimated to be 260,000 by gel filtration analysis, and that of a subunit was estimated to be 43,000 by sodium dodecyl sulfate-polyacrylamide gel analysis. Km values for reaction components were as follows: citrate, 6.25 mM; ATP, 650 microM; coenzyme A, 40.8 microM; and Mg2+, 8 mM. The enzyme showed citrate synthase activity in the presence of Mg2+, but the reaction rate was very low (less than 1/200 of the lyase activity).
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PMID:Purification and characterization of ATP:citrate lyase from Hydrogenobacter thermophilus TK-6. 270 59

The purpose of this investigation was to determine how models of weightlessness, hindlimb suspension (HS), and hindlimb immobilization (HI) affect the metabolic enzyme profile in the slow oxidative (SO), fast oxidative glycolytic (FOG), and fast glycolytic (FG) fibers of rat hindlimb. After 1, 2, or 4 wk of HS or HI, single fibers were isolated from freeze-dried soleus and gastrocnemius muscles; a small section of each fiber was run on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels to identify fiber type, and the remaining piece was assayed for either lactate dehydrogenase (LDH) and citrate synthase (CS) or phosphofructokinase (PFK) and beta-hydroxyacyl-CoA dehydrogenase (beta-OH-acyl-CoA). Two weeks of HS induced an almost twofold increase in the activity of CS (2.13 +/- 0.13 vs. 3.60 +/- 0.26 mol.kg dry wt-1.h-1) in the SO fiber of the soleus, and the activity stayed high at 4 wk. Although the FOG fiber had significantly higher CS activity (3.85 +/- 0.29) than either the SO or FG (1.59 +/- 0.16 mol.kg dry wt-1.h-1) fiber, neither fast fiber type was altered by HS. The glycolytic enzymes LDH and PFK were both elevated in the SO fiber after HS. The increase in LDH occurred by 1 wk (14.80 +/- 1.51 vs. 8.83 +/- 0.78), whereas the activity of PFK was not significantly changed until 4 wk (1.16 +/- 0.13 vs. 0.68 +/- 0.05 mol.kg dry wt-1.h-1). The control FG fiber had the highest LDH (44.30 +/- 2.29) and PFK (2.40 +/- 0.16) activities, followed by the FOG fiber (LDH, 34.10 +/- 2.83; PFK, 1.62 +/- 0.17 mol.kg dry wt-1.h-1); however, the activities of these glycolytic enzymes in the fast fiber types were unaltered by HS. The activity of beta-OH-acyl-CoA was not affected by HS in either the slow or fast fiber types. HI showed qualitatively similar changes to those observed with HS; however, the enzyme shifts developed with a slower time course. In conclusion, both HS and HI shifted the SO fiber enzyme pattern toward that of the control FOG fiber; however, a complete conversion from the SO to FOG fiber did not occur within the 4-wk treatment period.
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PMID:Single muscle fiber enzyme shifts with hindlimb suspension and immobilization. 271 97

Cultured renal collecting duct cells from neonatal rabbit kidney were used to examine the influence of aldosterone on enzymatic activity of citrate synthase during increase in Na+ transport. Control epithelia showed citrate synthase activity of 71 +/- 3 mU/mg protein (n = 28), while after aldosterone treatment citrate synthase activity was significantly increased to 79 +/- 6 mU/mg at 1 h (n = 5), to 88 +/- 6 mU/mg at 2 h (n = 6) and to 93 +/- 8 mU/mg protein at 3 h (n = 5). Citrate synthase activity subsequently decreased to basal values. Spironolactone fully blocked the aldosterone-induced increase in citrate synthase activity. The time course of enzyme stimulation after aldosterone administration indicates that the hormone activates citrate synthase during the physiological early response phase.
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PMID:Action of aldosterone on citrate synthase in cultured renal collecting duct cells. 276 67

The purified carbon monoxide dehydrogenase from Clostridium thermoaceticum is the only protein required to catalyze an exchange reaction between carbon monoxide and the carbonyl group of acetyl-CoA. This exchange requires that the CO dehydrogenase bind the methyl, the carbonyl, and the CoA groups of acetyl-CoA, then equilibrate the carbonyl with CO in the solution and re-form acetyl-CoA. CoA is not necessary for the exchange and, in fact, inhibits the reaction. These studies support the view that CO dehydrogenase is the condensing enzyme that forms acetyl-CoA from its component parts. Carbon dioxide also exchanges with the C-1 of acetyl-CoA, but at a much lower rate than does CO. At 50 degrees C and pH 5.3, the optimal pH, the turnover number is 70 mol of CO exchanged per min/mol of enzyme. Low potential electron carriers are stimulatory. The Km app for stimulation by ferredoxin is 50-fold less than the value for flavodoxin. Neither ATP or Pi stimulate the exchange. The EPR spectrum of the CO-reacted enzyme is markedly changed by binding of CoA or acetyl-CoA. Arginine residues of the CO dehydrogenase appear to be involved in the active site, possibly by binding acetyl-CoA. Mersalyl acid, methyl iodide, 5,5-dithiobis-(2-nitrobenzoate), and sodium dithionite inhibit the exchange reaction. A scheme is presented to account for the role of CO dehydrogenase in the exchange reaction and in the synthesis of acetate.
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PMID:Acetate biosynthesis by acetogenic bacteria. Evidence that carbon monoxide dehydrogenase is the condensing enzyme that catalyzes the final steps of the synthesis. 298 90

Exercise is associated with a net loss of K+ from the working muscles and an increased plasma K+ concentration, indicating that the capacity for intracellular reaccumulation of K+ is exceeded. Training reduces the exercise-induced rise in plasma K+, and an increased plasma [K+] may interfere with physical performance. Since the clearing of K+ from the extracellular space depends on the capacity for active K+ uptake in skeletal muscle, the effects of training and inactivity on the total concentration of (Na+ + K+)-ATPase was determined. Following 6 weeks of swim training, the concentration of [3H]ouabain-binding sites in rat hindlimb muscles was up to 46% (P less than 0.001) higher than in those obtained from age-matched controls. Whereas muscle Na+, K+ contents remained unchanged, the concentration of citrate synthase increased by up to 76% (P less than 0.001). Training induced no change in the [3H]ouabain-binding-site concentration in the diaphragm, but in the heart ventricles, the K+-dependent 3-O-methylfluorescein phosphatase activity increased by 20% (P less than 0.001). Muscle inactivity induced by denervation, plaster immobilisation or tenotomy reduced the [3H]ouabain-binding-site concentration by 20-30% (P less than 0.02-0.001) within 1 week. In conclusion, training leads to a significant and reversible rise in the concentration of (Na+ + K+)-ATPase in muscle cells. This may be of importance for the beneficial effects on physical performance by improving the maximum capacity for K+ clearance.
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PMID:Training increases the concentration of [3H]ouabain-binding sites in rat skeletal muscle. 301 29

Spheroplast membranes (spheroplast envelopes) of strain 2091 of group B Neisseria meningitidis were prepared by a procedure that included lysozyme treatment of the cells and osmotic lysis of the resulting spheroplasts. Electron microscopy revealed that the membranes consisted of two unit layers, generally parallel to each other. The membrane preparation migrated as a single component in a 40 to 70% sucrose gradient and consisted of 62% protein, 28% lipid, 9% ribonucleic acid, small amounts of carbohydrate, hexosamine, and deoxyribonucleic acid. When 1 or 10 mug (dry weight) was injected intravenously into rabbits, a mild pyrogenic reaction was elicited. In immunodiffusion tests, immune rabbit serum prepared against spheroplast membranes produced three major precipitin lines, with the homologous antigen solubilized with sodium dodecyl sulfate, and a single line with untreated antigen. The immune serum also reacted with a cell wall antigen, and to a lesser extent with some of the cytoplasmic antigens. Succinate dehydrogenase and reduced nicotinamide adenine dinucleotide (NADH) oxidase activities were found to be associated with the spheroplast membranes. NADH dehydrogenase also was associated with the membranes but was gradually released and recovered in other fractions. Glutamate-oxaloacetate transaminase, glutamate, glucose-6-phosphate, and isocitrate dehydrogenase activities were not found in the membrane preparation. About one-third of these enzymatic activities were recovered in the supernatant fluid after the sedimentation of the spheroplasts and two-thirds were recovered in the cytoplasmic fraction. N-acetylneuraminic acid (NAN)-condensing enzyme and cytidine monophosphate-NAN synthesizing enzyme also were identified in this organism. These enzymes were not associated with the membranes and were recovered from extracts from whole cells, spheroplasts, or cells exposed to osmotic shock, as well as from spheroplast supernatant and shock fluids. It is concluded that the spheroplast membranes of the strain of meningococci used in these studies are typical of those recovered from gram-negative bacteria.
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PMID:Characterization of spheroplast membranes of Neisseria meningitidis group B. 463 Jul 22


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