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

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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)

Interaction between the alpha-ketoglutarate dehydrogenase complex and NAD+-dependent isocitrate dehydrogenase was detected with a variety of techniques including polyethylene glycol precipitation, ultracentrifugation, and centrifugal gel filtration on a Sepharose 6B column. The interaction was specific in that citrate synthase, cytosolic malate dehydrogenase, and NADP-dependent isocitrate dehydrogenase did not interact with alpha-ketoglutarate dehydrogenase complex. The interaction was not inhibited by either 0.1 M KCl or 0.4 M (NH4)2SO4, but was completely prevented by 5% glycerol. A new method for the preparation of NADH: ubiquinone oxidoreductase resulted in an enzyme having a protein subunit composition similar to that of classical complex I preparation. Evidence is given for the existence of ternary complexes containing NADH:ubiquinone oxidoreductase-alpha-ketoglutarate dehydrogenase complex-NAD-dependent isocitrate dehydrogenase and NADH: ubiquinone oxidoreductase-alpha-ketoglutarate dehydrogenase complex-succinate thiokinase. These data suggest that a part of the citric acid cycle may be located in the vicinity of NADH: ubiquinone oxidoreductase. These complexes may facilitate the transport of metabolites among these enzymes without their equilibrating with the whole compartment.
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PMID:Interaction between NAD-dependent isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase complex, and NADH:ubiquinone oxidoreductase. 311 Jan 60

Studies by dynamic and total intensity light scattering, ultracentrifugation, electron microscopy, and chemical crosslinking on solutions of the pig heart mitochondrial enzymes, malate dehydrogenase and citrate synthase (separately and together) demonstrate that polyethylene glycol induces very large homoassociations of each enzyme, and still larger heteroenzyme complexes between these two enzymes in the solution phase. Specificity of this heteroassociation is indicated by the facts that heteroassociations with bovine serum albumin were not observed for either the mitochondrial dehydrogenase or the synthase or between cytosolic malate dehydrogenase and citrate synthase. The weight fraction of the enzymes in the mitochondrial dehydrogenase-synthase associated particles in the solution phase was less than 0.03% with the dilute conditions used in the dynamic light scattering measurements. Neither palmitoyl-CoA nor other solution conditions tested significantly increased this weight fraction of associated enzymes in the solution phase. Because of the extremely low solubility of the associated species, however, the majority of the enzymes can be precipitated as the heteroenzyme complex. This precipitation is a classical first-order transition in spite of the large particle sizes and broad size distribution. Ionic effects on the solubility of the heteroenzyme complex appear to be of general electrostatic nature. Polyethylene glycol was found to be more potent in precipitating this complex than dextrans, polyvinylpyrrolidones, ficoll, and beta-lactoglobulin.
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PMID:Polyethylene glycol-induced heteroassociation of malate dehydrogenase and citrate synthase. 366 37

3-Hydroxyacyl coenzyme A (CoA) dehydrogenase-binding protein was solubilized from inner mitochondrial membrane by using taurodeoxycholate at high ionic strength. The binding protein was isolated from the suspension using 3-hydroxyacyl-CoA dehydrogenase affinity chromatography. The protein eluted from the affinity column had a molecular weight of approximately 150,000, as determined by gel filtration. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the protein is a dimer consisting of 69,000 and 71,000 molecular weight subunits. The enzyme binding capacity of this protein was tested with a polyethylene glycol precipitation method: 0.5 mg of enzyme could be precipitated together with 1 mg of binding protein, showing that 1 mol of binding protein binds 1 mol of enzyme. This protein had no affinity toward malic dehydrogenase, citrate synthase, and fumarase. The approximately 2-fold increase in the 3-hydroxyacyl-CoA dehydrogenase activity when it was measured in the presence of the binding protein is additional evidence of enzyme-binding protein interaction. When incorporated into liposomes, the binding protein retained its ability to bind 3-hydroxyacyl-CoA dehydrogenase, but did not bind malic dehydrogenase, citrate synthase, and fumarase. These results suggest that the protein isolated by us has a specific function in anchoring a beta-oxidation enzyme to the matrix surface of the mitochondrial membrane.
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PMID:Isolation and characterization of 3-hydroxyacyl coenzyme A dehydrogenase-binding protein from pig heart inner mitochondrial membrane. 377 31

Thiolase, a mitochondrial matrix enzyme which produces CoASAc from fatty acids, is shown to interact with citrate synthase, the mitochondrial matrix enzyme responsible for CoASAc utilization. The interaction is demonstrated in three ways: the two enzymes co-precipitate in polyethylene glycol; thiolase causes a change in the fluorescence anisotropy of labeled citrate synthase; and the two enzymes co-elute in gel permeation chromatography. The interactions are shown to be specific by the use of enzymes not metabolically related to citrate synthase.
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PMID:Interaction between citrate synthase and thiolase. 383 93

Current evidence suggests that mitochondrial matrix enzymes exist in solid-state, multienzyme complexes in vivo. Addition of polyethylene glycol to a solution containing malate dehydrogenase and citrate synthase generates such a solid-state, enzyme complex in vitro at enzyme concentrations permitting kinetic measurements. Suspensions of the isolated, solid-state, hetero-complex of these enzymes were used to study the coupled reactions of citrate synthesis from malate, NAD, and CoASAc. The particles appear to be about 1 microgram in diameter. Considering the ratio of enzyme to oxalacetate molecules in or at the surface of the solid-state particles, one would expect oxalacetate to be converted to citrate within a few molecular distances of the site of oxalacetate generation. This model of "substrate channeling" (or alternatively a direct transfer of oxalacetate between enzymes) is supported by experiments with excess aspartate aminotransferase and glutamate added to the solution phase to give a reaction competing with the synthase for bulk phase oxalacetate. Quantities of aminotransferase that reduce the citrate reaction rate with soluble dehydrogenase and synthase by 90% do not significantly affect rates with comparable amounts of the dehydrogenase-synthase complex. We suggest that similar substrate channeling can occur in vivo and discuss the possible advantages provided thereby.
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PMID:Substrate channeling of oxalacetate in solid-state complexes of malate dehydrogenase and citrate synthase. 406 62

In this paper, physicochemical evidence is given for the association between the pyruvate dehydrogenase complex (EC 1.2.4.1) and citrate synthase (EC 4.1.3.7) with two gel chromatographic techniques with poly(ethylene glycol) co-precipitation and with ultracentrifugation. Experiments with active enzyme gel chromatography indicate that citrate synthase also associates with pyruvate dehydrogenase complex in its functioning state. Citrate synthase binds to the isolated transacetylase core of pyruvate dehydrogenase complex, but in the binding to the whole pyruvate dehydrogenase complex the two other components of the complex are also involved. One pyruvate dehydrogenase complex can bind 10-11 citrate synthase dimers, and the dissociation constant is about 5.7-6.0 microM as determined by two independent methods. The association between the pyruvate dehydrogenase complex and citrate synthase raises the possibility of the dynamic compartmentation of acetyl-CoA in the mitochondria which results in the direction of acetyl-CoA from pyruvate towards citrate.
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PMID:A study on the physical interaction between the pyruvate dehydrogenase complex and citrate synthase. 665 96

Experiments performed in polyethylene glycol and with a divalent crosslinker indicate that both mitochondrial malate dehydrogenase and aspartate aminotransferase can form hetero enzyme--enzyme complexes with either glutamate dehydrogenase or citrate synthase. In general, these as previous results indicate that complexes with the aminotransferase are favored over those with malate dehydrogenase and complexes with glutamate dehydrogenase are favored over those with citrate synthase. When the levels of enzymes are low, the only detectable complex is between the aminotransferase and glutamate dehydrogenase. Under these conditions, palmitoyl-CoA is required for complexes between the other three enzyme pairs, however, palmitoyl-CoA also enhances interactions between glutamate dehydrogenase and the aminotransferase. DPNH disrupts complexes with malate dehydrogenase and has little effect on those with the aminotransferase, while oxalacetate disrupts complexes with citrate synthase but has little effect on those with glutamate dehydrogenase. The citrate synthase-aminotransferase complex was favored in the presence of DPNH plus malate, which disrupt the other three enzyme-enzyme complexes. Glutamate dehydrogenase has a higher affinity and capacity than citrate synthase for palmitoyl-CoA. Consequently, lower levels of palmitoyl-CoA are required to enhance interactions with glutamate dehydrogenase. Furthermore, glutamate dehydrogenase can compete with citrate synthase for palmitoyl-CoA and thus can prevent palmitoyl-CoA from enhancing interactions between citrate synthase and either malate dehydrogenase or the aminotransferase.
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PMID:Complexes between mitochondrial enzymes and either citrate synthase or glutamate dehydrogenase. 682 31

Single crystals of citrate synthase from the Archaeon Thermoplasma acidophilum were obtained in two forms using the hanging drop vapour diffusion method and polyethylene glycol 3350 as precipitant. Type 1 crystals belong to the orthorhombic space group P222(1), with unit cell dimensions a = 80.9 A, b = 103.8 A, c = 98.3 A and one dimer in the asymmetric unit. Type 2 crystals belong to the monoclinic space group P2(1), with unit cell dimensions a = 53.8 A, b = 173.8 A, c = 86.7 A and beta = 97.1 degrees and two dimers in the asymmetric unit.
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PMID:Crystallization and preliminary crystallographic study of citrate synthase from the thermophilic Archaeon Thermoplasma acidophilum. 833 68

The interactions between pig heart citrate synthase and mitochondrial malate dehydrogenase or cytosolic malate dehydrogenase were studied using the frontal analysis method of gel filtration and by precipitation in polyethylene glycol. This method showed that an interaction between citrate synthase and mitochondrial malate dehydrogenase occurred but no interaction between citrate synthase and cytosolic malate dehydrogenase. Channeling of oxaloacetate in the malate dehydrogenase and citrate synthase-coupled systems was tested using polyethylene glycol precipitates of citrate synthase and mitochondrial malate dehydrogenase, and citrate synthase and cytosolic malate dehydrogenase. The effectiveness of large amounts of aspartate aminotransferase and oxaloacetate decarboxylase, as competing enzymes for the intermediate oxaloacetate, was examined. Aspartate aminotransferase and oxaloacetate decarboxylase were less effective competitors for oxaloacetate when precipitated citrate synthase and mitochondrial malate dehydrogenase in polyethylene glycol was used at low ionic strength compared with free enzymes in the absence of polyethylene glycol or with a co-precipitate of citrate synthase and cytosolic malate dehydrogenase. Substrate channeling of oxaloacetate with citrate synthase-mitochondrial malate dehydrogenase precipitate was inefficient at high ionic strength. These effects could be explained through electrostatic interactions of mitochondrial but not cytosolic malate dehydrogenase with citrate synthase.
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PMID:Interaction between citrate synthase and malate dehydrogenase. Substrate channeling of oxaloacetate. 979 62

The FK506 (tacrolimus)-binding protein (FKBP) type peptidyl-prolyl cis-trans isomerase (PPIase) in the hyperthermophilic archaeum Thermococcus sp. KS-1 was shown to be induced by temperature downshift to growth temperatures lower than the optimum. This PPIase (TcFKBP18) showed chaperone-like protein refolding activity in addition to PPIase activity in vitro. It refolded unfolded citrate synthase (CS) and increased the yield of the refolded protein. At a molar ratio of 15:1 ([TcFKBP18] to [CS]) in the refolding mixture, the recovered yield of folded CS was maximal at 62%, whereas that of spontaneous refolding was 11%. Increasing FKBP above a 15:1 ratio decreased the final yield, whereas the aggregation of unfolded CS was suppressed. A cross-linking analysis showed the formation of a complex between TcFKBP18 and unfolded CS (1:1 complex) at molar ratios of 3:1 to 15:1. However, molar ratios of 15:1 or 60:1 induced the binding of multiple FKBP molecules to an unfolded CS molecule (multimeric complex). Disrupting hydrophobic interaction by adding ethylene glycol at a molar ratio of 60:1 ([TcFKBP18] to [CS]) suppressed the formation of this multimeric complex, simultaneously enhancing CS refolding. FK506 also suppressed the formation of the multimeric complex while increasing the chaperone-like activity. These results suggest that the hydrophobic region of TcFKBP18, probably the FK506-binding pocket, was important for the interaction with unfolded proteins. No cross-linked product was detected between TcFKBP18 and native dimeric CS. TcFKBP18 probably traps the unfolded protein, then refolds and releases it in a native form. This FKBP might be important at growth temperatures lower than the optimum in Thermococcus sp. KS-1 cells.
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PMID:FK506-binding protein of the hyperthermophilic archaeum, Thermococcus sp. KS-1, a cold-shock-inducible peptidyl-prolyl cis-trans isomerase with activities to trap and refold denatured proteins. 1143 96


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