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 activities of citrate synthase, NAD-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase were measured in homogenates of soleus, diaphragm and heart muscles of the rat, in an attempt to define potential tricarboxylate cycle activity and its response to aging. Activities were significantly decreased in 24-month animals versus 6-month controls in every case (except 2-oxoglutarate dehydrogenase in heart muscle). Age-linked decrements were greatest in the soleus and least in heart. Cytochrome oxidase was measured as an index of total respiratory chain activity and decreased significantly in each case, with the smallest decrease in the heart. Acyl-CoA dehydrogenase and 3-hydroxyacyl-Co-A dehydrogenase were measured as an index of beta-oxidative activity; the former decreased in soleus and diaphragm, the latter in soleus and heart, with the decrease in the soleus being the greater. Carnitine acetyl- and palmitoyltransferases were measured, together with the muscle content of carnitine and acylcarnitine, as determining the potential rate of entry of acyl groups into the mitochondria for oxidation. Carnitine acetyltransferase activity was decreased with age in each of the muscles, but to the greatest extent in the heart. Carnitine palmitoyltransferase was decreased in both soleus and diaphragm. Carnitine content was decreased most in the soleus and the heart and to a lesser extent in the diaphragm. It is concluded that there is a generalized decline in oxidative activity in all of these muscles with age, on the basis of wet weight; this occurs to the greatest extent in the soleus and to the least extent in the heart. There is, in addition, a specific deficiency in the ability to oxidize fatty acids, relative to other substrates, in heart muscle.
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PMID:Age-linked changes in the activity of enzymes of the tricarboxylate cycle and lipid oxidation, and of carnitine content, in muscles of the rat. 628 24

The nucleotide sequence of a 3614 base-pair segment of DNA containing the sdhA gene, encoding the flavoprotein subunit of succinate dehydrogenase of Escherichia coli, and two genes sdhC and sdhD, encoding small hydrophobic subunits, has been determined. Together with the iron-sulphur protein gene (sdhB) these genes form an operon (sdhCDAB) situated between the citrate synthase gene (gltA) and the 2-oxoglutarate dehydrogenase complex genes (sucAB): gltA-sdhCDAB-sucAB. Transcription of the gltA and sdhCDAB gene appears to diverge from a single intergenic region that contains two pairs of potential promoter sequences and two putative CRP (cyclic AMP receptor protein)-binding sites. The sdhA structural gene comprises 1761 base-pairs (587 codons, excluding the initiation codon, AUG) and it encodes a polypeptide of Mr 64268 that is strikingly homologous with the flavoprotein subunit of fumarate reductase (frdA gene product). The FAD-binding region, including the histidine residue at the FAD-attachment site, has been identified by its homology with other flavoproteins and with the flavopeptide of the bovine heart mitochondrial succinate dehydrogenase. Potential active-site cysteine and histidine residues have also been indicated by the comparisons. The sdhC (384 base-pairs) and sdhD (342 base-pairs) structural genes encode two strongly hydrophobic proteins of Mr 14167 and 12792 respectively. These proteins resemble in size and composition, but not sequence, the membrane anchor proteins of fumarate reductase (the frdC and frdD gene products).
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PMID:Nucleotide sequence encoding the flavoprotein and hydrophobic subunits of the succinate dehydrogenase of Escherichia coli. 638 59

The nucleotide sequence of a 961 base-pair segment of DNA containing the sdhB gene, which encodes the iron-sulphur protein subunit of the E. coli succinate dehydrogenase, has been determined. The sdhB structural gene comprises 711 base pairs (237 codons, excluding the translational initiator and terminator). It is separated by a 15 base-pair intergenic region from the preceding flavoprotein gene (sdhA) and is the distal gene of an operon that also includes genes (sdhC and D) encoding two hydrophobic subunits, sdhCDAB. The distal end of the sdh operon is linked to the 2-oxoglutarate dehydrogenase gene (sucA) by a complex region of dyad symmetry that is homologous with several potential intercistronic regulatory elements or transcriptional attenuators. The sdhB structural gene encodes a polypeptide of Mr26637 that is strikingly homologous with the iron-sulphur protein subunit of fumarate reductase (38% identity, increasing to 58% when conservative changes are included). Both subunits contain 11 cysteine residues, 10 being conserved in three clusters resembling those found in ferredoxins. This work completes the sequence of a 9897 base-pair segment of DNA containing seven tricarboxylic acid cycle genes encoding three enzymes or enzyme complexes, citrate synthase (gltA), succinate dehydrogenase (sdh), and the 2-oxoglutarate dehydrogenase complex (suc), that are organized thus: gltA-sdhCDAB-sucAB.
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PMID:Nucleotide sequence encoding the iron-sulphur protein subunit of the succinate dehydrogenase of Escherichia coli. 638 71

In Bacillus subtilis, conditions causing partial deprivation of guanine nucleotides initiated sporulation and caused the synthesis of citrate synthase, aconitase, and alpha-ketoglutarate dehydrogenase. Alpha-ketoglutarate dehydrogenase could also be induced by acetate, and the specific activity of this enzyme was elevated in mutants that had high intracellular acetyl coenzyme A concentrations because they lacked citrate synthase activity. After deprivation of guanine nucleotides, the intracellular concentration of acetyl coenzyme A also increased, which explained the induction of alpha-ketoglutarate dehydrogenase. Furthermore, the decreases in alpha-ketoglutarate and L-malate concentrations observed during this deprivation accounted for the observed increases in citrate synthase activity (which was repressed by alpha-ketoglutarate and malate) and aconitase activity (which was repressed by alpha-ketoglutarate).
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PMID:Induction of citric acid cycle enzymes during initiation of sporulation by guanine nucleotide deprivation. 678 18

The activities of enzymes of the tricarboxylic acid cycle were measured in order to compare the respiratory capacity in different parts of the nephron of the rat. Oxoglutarate dehydrogenase, citrate synthase and isocitrate dehydrogenase were assayed in single nephron segments dissected out of freeze-dried cryostat sections. The activities of the three enzymes per unit weight are higher in the distal segments (thick ascending limb and distal convoluted tubule) than in the proximal tubule. The distal vs. proximal ratios of activities are about 1.5, 2.5 and 2 for oxoglutarate dehydrogenase, citrate synthase and isocitrate dehydrogenase, respectively. Oxoglutarate dehydrogenase shows the lowest activities along the whole nephron and appears to catalyze the rate-limiting step of the tricarboxylic acid cycle. The possibility to estimate the respiratory capacity in the different segments of the nephron on the basis of the activity of oxoglutarate dehydrogenase is discussed. The capacity calculated for the proximal tubule (between 44 and 66 mumol O X min-1 X g-1, depending on the substrate) is in agreement with direct measurements of oxygen consumption as well as with calculations made on the basis of morphometrical data.
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PMID:Activities of enzymes of the tricarboxylic acid cycle in segments of the rat nephron. 715 97

Rhodopseudomonas capsulata can grow in a number of alternative modes, including (i) photosynthetic, defined here as anaerobic growth with light as the energy source, and (ii) heterotrophic, referring to aerobic heterotrophic growth in darkness. The functions of citric acid cycle sequences in these growth modes were investigated using wild-type and appropriate mutant strains. Results of growth tests and O(2) utilization experiments showed that in the heterotrophic mode, energy conversion is dependent on operation of the classical citric acid cycle. Alpha-ketoglutarate dehydrogenase (KGD) activity in wild-type strain B10 is substantially higher in cells grown heterotrophically than in cells grown photosynthetically. Molecular oxygen, even at low concentration, appears to be important in regulation of KGD synthesis and, thus, in expression of citric acid cycle activity. Extracts of (photosynthetically grown) mutant strain KGD11 lack demonstrable KGD activity, and in contrast to the wild type, KGD11 is unable to grow heterotrophically on succinate, malate, or pyruvate owing to failure of the energy conversion function of the citric acid cycle. KGD11, however, grows well photosynthetically on malate or on CO(2) + H(2). The KGD activity level required to support the bioenergetic function of the citric acid cycle is evidently much higher than that necessary to satisfy biosynthetic demands; thus, a very low rate of succinyl-coenzyme A formation (needed for biosynthesis) in the mutant would suffice for growth under photosynthetic conditions. In wild-type R. capsulata, the alpha-ketoglutarate required for glutamate synthesis is ordinarily generated via citric acid cycle reactions, which include the conversions catalyzed by citrate synthase and isocitrate dehydrogenase. Mutants blocked in the former or both of these enzymes can grow photosynthetically if provided with an exogenous source of alpha-ketoglutarate or glutamate, but grow very poorly (if at all) as heterotrophs since the energy supply under these conditions depends on operation of the complete citric acid cycle.
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PMID:Biosynthetic and bioenergetic functions of citric acid cycle reactions in Rhodopseudomonas capsulata. 729 78

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

In an attempt to identify a possible defect of mitochondrial metabolism in Rett syndrome we studied 9 girls with typical Rett syndrome using a clinical protocol designed to identify disorders of oxidative metabolism. One girl, (RO) had marked lactic acidemia. Biochemical studies on samples from these patients included leukocyte pyruvate carboxylase assay, serum biotinidase and skin fibroblast pyruvate production, pyruvate dehydrogenase, citrate synthetase and 2-oxoglutarate dehydrogenase assay. Muscle electron transport activities were studied on samples from 4 typical Rett patients including RO. Mitochondrial DNA (mtDNA) mutational analysis for the np3243 MELAS mutation, the np8993 NARP mutation, the np8344 MERFF mutation and the 4977 kb common deletion found in Kearns-Sayre syndrome and aged tissues were tested for in 1 of the muscle samples and 2 blood samples from typical Rett patients. Western blotting of electron transport complex III was performed on mitochondrial samples obtained from autopsy brain tissue in 2 Rett patients and compared to pediatric control brain samples. No abnormalities were found in blood biotinidase or pyruvate carboxylase. Western blotting of 2 Rett brain mitochondrial samples for complex III appear normal. Pyruvate consumption in medium from 8 Rett fibroblast lines grown with and without dichloroacetate (DCA) showed a normal fall in pyruvate suggesting normal pyruvate dehydrogenase activity in these cells, however the fibroblasts from patient RO had a high pyruvate production in culture. Pyruvate dehydrogenase, 2-oxo-glutarate dehydrogenase and citrate synthetase activities in 8 Rett fibroblast lines were normal.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxidative metabolism in Rett syndrome: 2. Biochemical and molecular studies. 756 65

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

Activities of the tricarboxylic acid cycle enzymes were measured in subcellular fractions of liver from rats that had been fed clofibrate for 3 weeks. Large changes in these activities per gram tissue were found in the large particle fraction, which also showed an increase in total protein concentration of 76% under clofibrate treatment. The three regulatory enzymes of the cycle, namely citrate synthase, NAD(+)-linked isocitrate dehydrogenase, and 2-oxoglutarate dehydrogenase were significantly enhanced by 24% (P < 0.02), 54% (P < 0.02), and 153% (P < 0.005), respectively. Fumarase and malate dehydrogenase rose by 71% (P < 0.005) and 95% (P < 0.02), whereas succinate dehydrogenase remained unchanged. Enhancement of the citrate synthase, NAD-isocitrate dehydrogenase, and 2-oxoglutarate dehydrogenase may play a role in decreasing intracellular availability of acetyl-CoA for lipid metabolism.
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PMID:Clofibrate elevates enzyme activities of the tricarboxylic acid cycle in rat liver. 846 21


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