Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

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.
...
PMID:Propionyl-CoA condensing enzyme from Ascaris muscle mitochondria. I. Isolation and characterization of multiple forms. 199 Sep 76

This study investigates the effects of exogenous thyroxine (T4) on running endurance, tissue masses, and the activities of citrate synthase (CS), pyruvate kinase (PK), cytosolic alpha-glycerophosphate dehydrogenase (alpha-GPDH), and beta-hydroxyacyl Coenzyme A dehydrogenase (HOAD) in Sceloporus undulatus (eastern fence lizard). The enzymes were assayed to indicate maximal catabolic activities that support exercise. Parallel experiments were done on captive and field-active groups to determine whether responses in captive studies adequately predict responses in nature. Exogenous T4 was administered via intraperitoneal pellets. The effect of T4 on running endurance was dependent on the location of the experiment (P = 0.040) such that stamina was increased by T4 only in field-active lizards. At lower levels of biological organization, interactivity between T4 and experimental location was evident but less prevalent than at the level of the whole animal, and some location effects occurred independent of T4 treatment. Heart and kidney masses were significantly greater and total hind leg muscle mass was less in captive than in field-active lizards. Thyroxine reduced liver mass in both locations and kidney mass only in captive lizards. Mass-specific CS and alpha-GPDH in gastrocnemius muscle (mixed fiber type) and HOAD in heart were lower in captive than in field-active lizards; PK in heart and liver and alpha-GPDH in heart were higher in captive lizards. Thyroxine increased CS in liver and HOAD in heart, decreased alpha-GPDH in liver in both locations, and decreased alpha-GPDH in gastrocnemius only in captive lizards. The effects of T4 differed significantly between experimental locations in gastrocnemius muscle (T4 decreased PK only in captive lizards) and in liver (T4 increased PK in field-active lizards and decreased PK in captive lizards). The mechanistic basis of differences in stamina between captive and field-active and between placebo and T4-treated lizards is largely unexplained by the factors measured here, thus illustrating the uncertainty of predicting organismal performance from lower level measurements. Nonetheless, T4 has now been shown to have greater physiological activity in field-active than in captive Sceloporus with regard to resting and total daily metabolic rates and running endurance. The results of this study further confirm that endocrine experiments on captive animals may not predict responses in nature. Further efforts to clarify the physiological significance of seasonal variations in levels of thyroid hormones will have to involve, at least in part, invasive studies on field-active lizards.
...
PMID:Interactive effects of thyroxine and experimental location on running endurance, tissue masses, and enzyme activities in captive versus field-active lizards (Sceloporus undulatus). 202 10

Using long-chain fatty acyl CoAs (arachidoyl CoA and behenoyl CoA), a decrease in overall fatty acid chain elongation activity was observed in the quaking and jimpy mouse brain microsomes relative to controls. Arachidoyl CoA (20:0) and behenoyl CoA (22:0) elongation activities were depressed to about 50% and 80% of control values in quaking and jimpy mice, respectively. Measurement of the individual enzymatic activities of the elongation system revealed a single deficiency in enzyme activity; only the condensation activity was reduced to the same extent as total elongation in both quaking and jimpy mice. The activities of the other three enzymes, beta-ketoacyl CoA reductase, beta-hydroxyacyl CoA dehydrase, and trans-2-enoyl CoA reductase, in both mutants were similar to the activities present in the control mouse. In addition, the activities of these three enzymes were more than two to three orders of magnitude greater than the condensing enzyme activity in all three groups, establishing that the condensing enzyme catalyzes the rate-limiting reaction step of total elongation. When the elongation of palmitoyl CoA was measured, only a 25% decrease in total elongation occurred in both mutants; a similar percent decrease in the condensation of palmitoyl CoA also was observed. The activities of the other three enzymes were unaffected. These results support the concept of either multiple elongation pathways or multiple condensing enzymes.
...
PMID:Decreased long-chain fatty acyl CoA elongation activity in quaking and jimpy mouse brain: deficiency in one enzyme or multiple enzyme activities? 205 Nov 61

Previous studies have shown that dietary provision of carbohydrate can alter cardiac isomyosin distribution in hormonally deficient rats. The main objective of this study was to determine if varying the heart's potential to utilize carbohydrate for energy provision can influence the cardiac isomyosin expression in normal weanling rats. Animals were assigned to one of five groups according to dietary and/or metabolic treatment: (1) mixed-control--(M); (2) high carbohydrate--(H); (3) low carbohydrate--(L); (4) mixed-diet supplemented with oxfenicine, a cardiospecific fatty acid oxidation inhibitor--(MO); and (5) high carbohydrate diet supplemented with oxfenicine--(HO). The results show that 4 weeks of dietary manipulations aimed to either increase or decrease carbohydrate supply to the heart, failed to induce any alterations in either cardiac myosin ATPase activity or isoenzyme pattern. However, extremes in carbohydrate provision altered the metabolic properties of both heart and skeletal muscle. A low carbohydrate diet increased 3-hydroxyacyl CoA dehydrogenase (P less than 0.05) and citrate synthase activities (P less than 0.05) and decreased glycogen content in both heart and soleus muscle; whereas, a high carbohydrate diet, in conjunction with oxfenicine, tended to increase hexokinase activity in these same tissues. These alterations provide indirect evidence that the contributions of both fat and carbohydrate to the energy balance of the heart and skeletal muscle were altered by the imposed dietary interventions. Collectively, these results suggest that although the substrate utilization patterns of the normal weanling heart can be modified via dietary manipulation, such shifts do not exert any regulatory influence on cardiac isomyosin expression.
...
PMID:Dietary effects on cardiac metabolic properties in rodents. 214 63

The aza analogue (RS)-3-hydroxy-2,5-pyrrolidinedione-3-acetic acid (6) of the five-membered citric anhydride (2) was prepared in the sequence citric acid----2-phenyl-1,3-dioxolan-4-one-5,5-diacetic acid (1)----citric acid beta-amide (3)----6 and used to resolve ambiguities in the mechanism of the citrate synthase reaction. The results yield no indication for the formation of anhydride 2 on the enzyme and favour the direct hydrolysis of the intermediate (3S)-citryl-CoA. Ammonolysis of the dioxolanone 1 in the reaction sequence described above produced not only citric acid beta-amide but also the alpha-isomer. This is shown to originate in the transient formation of anhydride 2. Hydrolysis of the dioxolanone 1 under "physiological conditions" occurs via anhydride 2, generated in intramolecular bifunctional catalysis by a protonated and a deprotonated carboxyl group. The catalytic residue Asp375 of citrate synthase is considered to operate on the enzyme as does the protonated carboxyl group in the chemical reaction and to generate enolic acetyl-CoA in cooperative catalysis with His274. This reaction of Asp375 may also facilitate the hydrolysis of citryl-CoA.
...
PMID:On the action of carboxy groups in the citrate synthase reaction. 220 58

Recent studies in patients with long-term heart failure have suggested that intrinsic abnormalities in skeletal muscle can contribute to the development of early lactic acidosis and fatigue during exercise. The present study provides an analysis of substrate and enzyme content, fiber typing, and capillarization in skeletal muscle biopsy samples obtained at rest from the vastus lateralis in 11 patients with long-term heart failure (left ventricular ejection fraction, 21 +/- 8%) and nine normal subjects. Patients demonstrated a reduced peak exercise oxygen consumption (13.0 +/- 3.3 ml/kg/min) when compared with normals (30.2 +/- 8.6 ml/kg/min, p less than 0.001) and had an accelerated rise in blood lactate levels during exercise. In mixed fiber skeletal muscle, total phosphorylase and glycolytic enzyme activities were not different in the two groups, whereas mitochondrial enzymes involved in terminal oxidation were decreased in patients as compared with normal subjects as indicated by reductions in succinate dehydrogenase (51 +/- 15 vs. 81 +/- 17 microM/g protein/min, p less than 0.001) and citrate synthetase (26 +/- 7 vs. 43 +/- 20 microM/g protein/min, p less than 0.05). 3-Hydroxyacyl-CoA-dehydrogenase, an important enzyme mediating beta-oxidation of fatty acids, was also reduced in patients as compared with normals (18 +/- 7 vs. 27 +/- 10 microM/g protein/min, p less than 0.05). There was no difference in high-energy phosphagens or lactate concentration of mixed muscle in the two groups, whereas glycogen content was decreased in patients (262 +/- 29 vs. 298 +/- 35 microM glucosyl units/kg dry wt, p = 0.01). Patients demonstrated a reduced percentage of slow twitch type I fibers (36 +/- 7% vs. 52 +/- 22%, p less than 0.05) and had a higher percentage of type IIb fast twitch fibers (24 +/- 9% vs. 11 +/- 12%, p = 0.02), which were smaller than the type IIb fibers seen in normal subjects (p less than 0.05). In patients, the number of capillaries per fiber was decreased for type I and type IIa fibers (both, p less than 0.03), but the ratio of capillaries to cross-sectional fiber area was not different for the two groups. These data demonstrate major alterations in skeletal muscle histology and biochemistry in patients with long-term heart failure, including fiber atrophy, a decrease in percentage of composition of type I fibers, and an increase in type IIb fibers accompanied by a decrease in oxidative enzyme capacity.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Skeletal muscle biochemistry and histology in ambulatory patients with long-term heart failure. 229 59

Radioisotopic assays for the determination of acetyl-CoA, CoASH, and acetylcarnitine have been modified for application to the amount of human muscle tissue that can be obtained by needle biopsy. In the last step common to all three methods, acetyl-CoA is condensed with [14C]oxaloacetate by citrate synthase to give [14C]-citrate. For determination of CoASH, CoASH is reacted with acetylphosphate in a reaction catalyzed by phosphotransacetylase to yield acetyl-CoA. In the assay for acetylcarnitine, acetylcarnitine is reacted with CoASH in a reaction catalyzed by carnitine acetyltransferase to form acetyl-CoA. Inclusion of new simple steps in the acetylcarnitine assay and conditions affecting the reliability of all three methods are also described. Acetylcarnitine and free carnitine levels in human rectus abdominis muscle were 3.0 +/- 1.5 (SD) and 13.5 +/- 4.0 mumol/g dry wt, respectively. Values for acetyl-CoA and CoASH were about 500-fold lower, 6.7 +/- 1.8 and 21 +/- 8.9 nmol/g dry wt, respectively. A strong correlation between acetylcarnitine (y) and short-chain acylcarnitine (x), determined as the difference between total and free carnitine, was found in biopsies from the vastus lateralis muscle obtained during intense muscular effort, y = 1.0x + 0.5; r = 0.976.
...
PMID:Radioisotopic assays of CoASH and carnitine and their acetylated forms in human skeletal muscle. 233 83

The orientation of the condensing enzyme, the beta-hydroxyacyl-CoA dehydrase, and the trans-2-enoyl CoA reductase within the rat liver microsomal membrane was investigated by the use of impermeant inhibitors of enzyme activity: trypsin, chymotrypsin, subtilisin, mercury-dextran, and anti-beta-hydroxyacyl-CoA dehydrase IgG. The activity of the condensing enzyme was inhibited more than 70% by various proteases and was completely inhibited by 80 microM mercury-dextran. Similar results were obtained for the trans-2-enoyl-CoA reductase activity. On the other hand, in the absence of detergent, proteases inhibited beta-hydroxyacyl-CoA dehydrase activity by 25-40%, while in the presence of detergent the inhibition increased to 65-90%. Furthermore, anti-beta-hydroxyacyl-CoA dehydrase IgG, which in the absence of detergent produced no inhibition, in the presence of detergent inhibited beta-hydroxyacyl-CoA dehydrase activity by more than 80%; under identical conditions, preimmune IgG caused a 13% inhibition. Microsomes used throughout this study displayed greater than 90% latency with respect to mannose-6-phosphatase activity, indicating that the microsomes were intact. Latency was not affected by the proteases, by mercury-dextran, or by the presence of the enzyme assay components. These results suggest that both the condensing enzyme and the reductase are present on the cytoplasmic surface of the membrane, whereas the beta-hydroxyacyl-CoA dehydrase is embedded in the microsomal membrane.
...
PMID:Topography of rat hepatic microsomal enzymatic components of the fatty acid chain elongation system. 254 Jan 64

Tissue samples were obtained from the vastus lateralis muscle of elite olympic weight and power lifters (OL/PL, n = 6), bodybuilders (BB, n = 7), and sedentary men (n = 7). Enzyme activities of citrate synthase (CS), lactate dehydrogenase (LD), 3-OH-acyl-CoA-dehydrogenase (HAD), and myokinase (MK) were assayed on freeze-dried dissected pools of slow-twitch (ST) and fast-twitch (FT) fiber fragments by fluorometric means. Histochemical analyses were carried out to assess fiber type composition and fiber area. CS and HAD activities were lower (P less than 0.05), and LD and MK were higher (P less than 0.05) in FT than ST fibers in the entire subject pool (n = 20). CS of FT fibers and HAD of ST fibers were lower in athletes (P less than 0.05-0.01) compared with nonathletes, whereas LD of both fiber types was higher (P less than 0.05-0.001) in athletes. CS activity of ST fibers and MK activity of FT fibers were higher (P less than 0.05) in BB compared with OL/PL. FT and ST fiber area was greater (P less than 0.05) in athletes than in nonathletes. BB displayed greater (P less than 0.05) fiber size than OL/PL. FT/ST area was greater (P less than 0.05) in OL/PL than BB. It is suggested that long-term heavy-resistance training results in specific metabolic adaptations of FT and ST fiber types. These changes appear to be influenced by the type of resistance training.
...
PMID:Enzyme activities of FT and ST muscle fibers in heavy-resistance trained athletes. 254 51

Aspects of energetic and intermediary metabolism were studied in a colon adenocarcinoma cell line (HT29) by multinuclear magnetic resonance spectroscopy. Experiments were carried out on the HT29-D4 clone, which was isolated by limit dilution techniques. This clone, usually undifferentiated (D4-UD), can be maintained in a differentiated state (D4-D) in a glucose-free medium. Metabolic data were obtained by NMR analysis of perchloric acid extracts from D4-UD and D4-D cells. Phosphorus-31 and proton NMR spectra showed the presence of a large amount of choline and phosphorylcholine in the differentiated state (400% and 200%, respectively, of the levels found in D4-UD cells). Other differences appeared in the content of phosphocreatine (absent in D4-D cells) and myoinositol (absent in D4-UD cells). Carbon-13 spectra were recorded from perchloric acid extracts of cells incubated with [1-13C]-labeled glucose or [2-13C]-labeled acetate. The data indicated that both types of cells metabolize glucose through the glycolytic pathway to give lactate, but only D4-D cells were able to store glucose as glycogen at a very high level. A mathematical analysis of fluxes through the tricarboxylic acid (TCA) cycle was developed on the basis of models derived from previous 14C tracer studies. The model was based on the steady-state labeling of glutamate carbons by the 13C isotope and gave the fraction of labeled acetyl-Coa entering the TCA cycle, and the activity y of anaplerotic reactions relative to the flux through the citrate synthetase reaction. The data indicated that y greater than 0.3 in all cases. Only 15% and 30% of labeled acetyl CoA entered the TCA cycle in D4-UD and D4-D cells, respectively, under labeled glucose incubation: these values were significantly different upon labeled acetate feeding, reaching 55% for D4-UD cells and 85% for D4-D cells. The main result of this study is that the process of differentiation of HT29 cells is correlated with a large increase in the activity of oxidative metabolism.
...
PMID:Metabolic changes in undifferentiated and differentiated human colon adenocarcinoma cells studied by multinuclear magnetic resonance spectroscopy. 255 31


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---