Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxygen consumption was measured before and during infusion of the catecholamine isoproterenol in age-matched spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive rats. Mass-independent rates of oxygen consumption of anesthetized 7-week-old rats were similar in the WKY and SHR rats (11.08 +/- 0.74 and 11.33 +/- 0.82 ml O2 min-1 kg-.67, respectively). Catecholamine infusion elicited increased total oxygen consumption in both WKY and SHR animals (15.0 +/- 1.0 and 14.9 +/- 1.2 ml O2 min-1 kg-.67, respectively), and the magnitude of these increases did not significantly differ. To assess whether there were changes in the metabolic state of brown adipose tissue, the major site of catecholamine-induced thermogenesis in rats, enzymes whose activity is proportional to aerobic capacity were assayed in vitro. In both the interscapular and cervical brown fat depots, maximal citrate synthase and maximal HOAD (beta-hydroxyacyl-CoA dehydrogenase) activities were similar in SHR and WKY rats. There were also no significant differences in brown fat protein content, suggesting no differential growth of this tissue in the two rat strains. Our results indicate that the nonshivering thermogenic capacity of the hypertensive SHR rats does not differ from that of the normotensive WKY animals.
Proc Soc Exp Biol Med 1988 Sep
PMID:Nonshivering thermogenesis and brown fat in spontaneously hypertensive rats. 342 Jan 7

Management of adenine nucleotide catabolism differs among skeletal muscle fiber types. This study evaluated whether there are corresponding differences in the rates of de novo synthesis of adenine nucleotide among fiber type sections of skeletal muscle using an isolated perfused rat hindquarter preparation. Label incorporation into adenine nucleotides from the [1-14C]glycine precursor was determined and used to calculate synthesis rates based on the intracellular glycine specific radioactivity. Results show that intracellular glycine is closely related to the direct precursor pool. Rates of de novo synthesis were highest in fast-twitch red muscle (57.0 +/- 4.0, 58.2 +/- 4.4 nmol.h-1.g-1; deep red gastrocnemius and vastus lateralis), relatively high in slow-twitch red muscle (47.0 +/- 3.1; soleus), and low in fast-twitch white muscle (26.1 +/- 2.0 and 21.6 +/- 2.3; superficial white gastrocnemius and vastus lateralis). Rates for four mixed muscles were intermediate, ranging between 32.3 and 37.3. Specific de novo synthesis rates exhibited a strong correlation (r = 0.986) with muscle section citrate synthase activity. Turnover rates (de novo synthesis rate/adenine nucleotide pool size) were highest in high oxidative muscle (0.82-1.06%/h), lowest in low oxidative muscle (0.30-0.35%/h), and intermediate in mixed muscle (0.44-0.55%/h). Our results demonstrate that differences in adenine nucleotide management among fiber types extends to the process of de novo adenine nucleotide synthesis.
Am J Physiol 1988 Sep
PMID:De novo synthesis of adenine nucleotides in different skeletal muscle fiber types. 342 9

Muscle biopsy samples were collected from the middle gluteal muscle of seven horses undergoing a nine-month endurance training programme. Samples were collected before the programme began and again after three, six and nine months of training. A fifth sample was collected three months after training ceased. Serial muscle sections were reacted histochemically for myosin adenosine triphosphatase after either acid (pH 4.3 and 4.6) or alkaline (pH 10.3) pre-incubation, and muscle fibres identified as type I, IIA, IIB or IIC. The oxidative capacity of individual fibres was assessed, using the reduced nicotinamide dinucleotide tetrazolium reductase stain, and the number of intermyofibrillar capillaries adjacent to each fibre was counted after staining, using the alpha-amylase periodic acid Schiff technique. Biochemical analyses involved the fluorometric measurement of the enzymes citrate synthase, 3-hydroxy acyl CoA dehydrogenase and lactate dehydrogenase as markers of end terminal oxidative, beta oxidative and glycolytic potential, respectively. There was an increase in the percentage of type IIB fibres having high nicotinamide dinucleotide tetrazolium reductase staining after three months training. This increase persisted throughout the period of training and during the period without training. There was an increase in the number of capillaries adjacent to type IIB fibres after six and nine months training. These had returned to near pre-training numbers after three months without training. There were increases in the activities of citrate synthase and 3-hydroxy acyl CoA dehydrogenase after three months training. The activities of both enzymes continued to rise throughout training and the highest activities were attained after nine months.(ABSTRACT TRUNCATED AT 250 WORDS)
Vet Rec 1987 Sep 19
PMID:Effects of a nine-month endurance training programme on muscle composition in the horse. 367 37

The effect of severe protein deprivation and subsequent nutritional rehabilitation on the fibre size and mitochondrial enzyme activity of the extensor digitorum longus (EDL) and soleus muscles of the young rat has been examined. Protein deprived rats showed atrophy of type 2 fibres predominantly, reduced histochemical activity of succinic dehydrogenase (SDH) and reduced biochemical activity of citrate synthase. Nutritional rehabilitation indicated by resumption of the original body weight resulted in complete restitution of the weight of the muscles and the size of type 1 and type 2 fibres, but not of the activity of SDH and citrate synthase. The results indicate that regarding size, type 2 fibres tend to be more influenced than type 1 fibres by the nutritional supply. The mitochondrial enzyme activity which is decreased by protein deprivation does not regain the normal levels as quickly as the muscle fibres resume their normal size.
J Neurol Sci 1986 Sep
PMID:Nutritional rehabilitation of skeletal muscle in protein-deprived young rats. 376 Sep 9

The enzyme activity of the pyruvate dehydrogenase complex (PDHC) was measured in mitochondria prepared from developing rat brain, before and after steady-state dephosphorylation of the E1 alpha subunit. A marked increase in dephosphorylated (fully activated) PDHC activity occurred between days 10 and 15 post partum, which represented approx. 60% of the difference in fully activated PDHC activity measured in foetal and adult rat brain mitochondria. There was no detectable change in the active proportion of the enzyme during mitochondrial preparation nor any qualitative alteration in the detectable catalytic and regulatory components of the complex, which might account for developmental changes in PDHC activity. The PDHC protein content of developing rat brain mitochondria and homogenates was measured by an enzyme-linked immunoadsorbent assay. The development of PDHC protein in both fractions agreed closely with the development of the PDHC activity. The results suggest that the developmental increase in PDHC activity is due to increased synthesis of PDHC protein, which is partly a consequence of an increase in mitochondrial numbers. However, the marked increase in PDHC activity measured between days 10 and 15 post partum is mainly due to an increase in the amount of PDHC per mitochondrion. The development of citrate synthase enzyme activity and protein was measured in rat brain homogenates and mitochondria. As only a small increase in citrate synthase activity and protein was detected in mitochondria between days 10 and 15 post partum, the marked increase in PDHC protein and enzyme activity may represent specific PDHC synthesis. As several indicators of acquired neurological competence become apparent during this period, it is proposed that preferential synthesis of PDHC may be crucial to this process. The results are discussed with respect to the possible roles played by PDHC in changes of respiratory-substrate utilization and the acquisition of neurological competence occurring during the development of the brain of a non-precocial species such as the rat.
Biochem J 1986 Sep 15
PMID:Comparative development of the pyruvate dehydrogenase complex and citrate synthase in rat brain mitochondria. 380 Sep 58

Samples of bovine muscle (post rigor) were frozen at different temperatures between -5 degrees and -196 degrees C at different freezing rates, and thawed at room temperature. The activities of the mitochondrial enzymes lipoamide dehydrogenase, citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase were determined in the supernatant of the tissue homogenates in phosphate buffer (total enzyme activity), as well as in the press juice of the intact tissue (enzyme activity in the sarcoplasma). Neither the temperature nor the rate of freezing (varying from 25.5 to 0.01 min/degrees C) showed a significant influence on the total enzyme activities. Freezing at -5 degrees and -10 degrees C (at different rates but without intracellular freezing) and thawing did not result in an appreciable release of enzymes. Below -10 degrees C the release of the three enzymes from their binding to the inner membrane of the mitochondrion into the sarcoplasmic fluid increased upon rapid freezing with decreasing temperature i.e. with increasing intracellular ice formation, whereas at slow freezing (with extracellular ice formation only) freezing below -20 degrees C did not cause further enzyme release. At freezing temperatures below -20 degrees C rapid freezing resulted in a significantly stronger release of the three enzymes than slow freezing. From these results it was concluded that the damage to mitochondrial membranes upon fast freezing is primarily a result of intracellular (and perhaps also intramitochondrial) ice formation, whereas the membrane damage during slow freezing is primarily due to dehydration caused by the migration of water from the muscle fibers into the extracellular space as a result of osmotic effects. Ion concentration in the nonfreezing fraction of tissue water seems to be only of minor importance for the disintegration of mitochondrial membranes.
Z Lebensm Unters Forsch 1985 Sep
PMID:[Lipoamide dehydrogenase, citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase in skeletal muscle. VIII. The influence of temperature and rate of freezing of bovine muscle on the activity and subcellular distribution of the enzymes in the thawed tissue]. 384 Mar 12

Sonic oscillation of mitochondria usually leads to the release of a number of Krebs tricarboxylic acid cycle enzymes. These enzymes have, therefore, been referred to as soluble matrix enzymes. In the present report, we show that gentle sonic or osmotic disruption can be used to obtain a mitochondrial preparation where these enzymes appear to be organized in a large complex of proteins. Using citrate synthase as a marker for these enzymes, we show that the proposed complex is easily sedimented at 32,000 X g in 30 min. The exposed citrate synthase in these complexes can be inhibited by its antibody, indicating that the enzymes are not merely entrapped in substrate-permeable vesicles. The effects of pH, temperature, ionic strength, and several metabolites on the ability to obtain the sedimentable citrate synthase have been tested. These studies indicate that the complex is stable at conditions presumed to exist in situ. Electron microscopic studies show that gentle sonic oscillation gives rise to an efflux of mitochondrial matrix contents which tend to remain attached to the original membranes. The sedimentable fraction also contained four other presumably soluble Krebs tricarboxylic acid cycle enzymes: aconitase, NAD+-isocitrate dehydrogenase, fumarase, and malate dehydrogenase.
J Biol Chem 1985 Sep 05
PMID:Organization of Krebs tricarboxylic acid cycle enzymes in mitochondria. 403 Jul 72

The necessity for adding an internal standard to liver extracts during fluorimetric estimation of acetyl-CoA by the malic dehydrogenase-citrate synthase reaction is demonstrated. Addition of acetyl-CoA completely compensates for the inhibitory action of some tissue components. Values for hepatic acetyl-CoA in fed and fasted rats are given.
J Lipid Res 1967 Sep
PMID:Internal standards in the estimation of acetyl-CoA in liver extracts. 429 62

An immobilized three-enzyme system, malate dehydrogenase (EC 1.1.1.37)-citrate synthase (EC 4.1.3.7)-lactate dehydrogenase (EC 1.1.1.27), was investigated as a model for the rate of oxalacetate production and utilization in mitochondria. Lactate dehydrogenase is included to mimic the NADH-utilizing system of mitochondria. This three-enzyme system was immobilized in three different ways (1) on Sephadex G-50 (surface coupling), (2) on Sepharose 4B (internal-external coupling), and (3) entrapped in polycrylamide gel. The rate of citrate production from malate, NAD(+), and acetyl CoA was determined continuously in a flow system. Up to about 100% rate enhancements were observed when the immobilized system was compared to identical systems of free enzyme. An even more pronounced increase of rate of up to about 400% compared to the soluble system was measured after addition of pyruvate (to reoxidize formed NADH). These results are interpreted in relation to microenvironmental changes of oxalacetate production and the possible organization of enzymes of the Krebs cycle.
Proc Natl Acad Sci U S A 1973 Sep
PMID:An immobilized three-enzyme system: a model for microenvironmental compartmentation in mitochondria. 435 55

(1) A ;cycling' method involving citrate synthase (EC 4.1.3.7) and malate dehydrogenase (EC 1.1.1.37) was modified by the inclusion of succinyl-CoA synthetase (EC 6.2.1.5) and hexokinase (EC 2.7.1.1) to permit the determination of very small amounts of succinyl-CoA in addition to CoA and acetyl-CoA. (2) Application of this technique to blowfly (Phormia regina) flight-muscle extracts reveals no change in acetyl-CoA concentration, a slight fall in CoA concentration and a rise in succinyl-CoA concentration during flight. (3) Extraction of isolated mitochondria during controlled (state 4) pyruvate oxidation reveals essentially only acetyl-CoA. Activation of respiration by ADP (state 3) or uncoupling agents leads to a fall in acetyl-CoA and a rise in CoA and succinyl-CoA content. (4) The presence of glycerol phosphate in addition to pyruvate results in a lower acetyl-CoA content in state 4. (5) It is contended that these results are consistent with a primary control of one of the reactions of the tricarboxylate cycle, rather than of pyruvate dehydrogenase, during the state 4 oxidation of pyruvate by isolated mitochondria, and that the modulation of citrate synthase activity by the ratio of acetyl-CoA/succinyl-CoA is unimportant under these conditions.
Biochem J 1974 Sep
PMID:The control of tricarboxylate-cycle of oxidations in blowfly flight muscle. The steady-state concentrations of coenzyme A, acetyl-coenzyme A and succinyl-coenzyme A in flight muscle and isolated mitochondria. 446 39


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