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Query: EC:1.1.1.41 (isocitrate dehydrogenase)
 3,101 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of the eight citric acid-cycle enzymes of rat bone-marrow cells were determined along with several other mitochondrial and non-mitochondrial enzymes. Four of the citric acid-cycle enzymes (aconitase, succinyl-CoA thiokinase, alpha-oxoglutarate dehydrogenase and succinate dehydrogenase) have closely similar low activities; two [isocitrate dehydrogenase (NAD) and citrate synthase] have intermediate activities; the remaining two (malate dehydrogenase and fumarase) have high activities. The other enzymes surveyed also exhibited a spread of three orders of magnitude, the mitochondrial enzymes showing no less variation than the others.
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PMID:The activities of the citric acid-cycle enzymes in rat bone-marrow cells. 566 55

Treatment of rat liver mitochondria with digitonin followed by differential centrifugation was used to resolve the intramitochondrial localization of both soluble and particulate enzymes. Rat liver mitochondria were separated into three fractions: inner membrane plus matrix, outer membrane, and a soluble fraction containing enzymes localized between the membranes plus some solublized outer membrane. Monoamine oxidase, kynurenine hydroxylase, and rotenone-insensitive NADH-cytochrome c reductase were found primarily in the outer membrane fraction. Succinate-cytochrome c reductase, succinate dehydrogenase, cytochrome oxidase, beta-hydroxybutyrate dehydrogenase, alpha-ketoglutarate dehydrogenase, lipoamide dehydrogenase, NAD- and NADH-isocitrate dehydrogenase, glutamate dehydrogenase, aspartate aminotransferase, and ornithine transcarbamoylase were found in the inner membrane-matrix fraction. Nucleoside diphosphokinase was found in both the outer membrane and soluble fractions; this suggests a dual localization. Adenylate kinase was found entirely in the soluble fraction and was released at a lower digitonin concentration than was the outer membrane; this suggests that this enzyme is localized between the two membranes. The inner membrane-matrix fraction was separated into inner membrane and matrix by treatment with the nonionic detergent Lubrol, and this separation was used as a basis for calculating the relative protein content of the mitochondrial components. The inner membrane-matrix fraction retained a high degree of morphological and biochemical integrity and exhibited a high respiratory rate and respiratory control when assayed in a sucrose-mannitol medium containing EDTA.
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PMID:Enzymatic properties of the inner and outer membranes of rat liver mitochondria. 569 70

During exponential growth, ordinary colorless (OC) plants of Blastocladiella emersonii consumed little glucose and produced no lactic acid. Similarly, resistant sporangial (RS) plants did not utilize glucose or produce lactic acid during the first 24 hr of exponential growth. During the next 24 hr of RS development, glucose was consumed with the concomitant production of lactic acid which was then reutilized. Lactic acid gradually accumulated again at maturity. Enzyme studies on cell-free extracts indicated the presence of all tricarboxylic cycle enzymes except alpha-ketoglutarate dehydrogenase at all stages of development of both RS and OC plants. Included among the enzymes detected were an adenosine monophosphate-stimulated, nicotinamide adenine dinucleotide-isocitric dehydrogenase, and citrate-condensing enzyme. When measured on a per plant basis, tricarboxylic cycle enzyme levels increased during the exponential growth of both kinds of plants. Only after the bicarbonate ceased to have effect on RS plant morphogenesis was there a decrease in the levels of the tricarboxylic cycle enzymes when measured on a per plant basis. Specific activity measurements indicated some differences in the differential rates of synthesis among the enzymes studied previous to 36 hr. Preliminary studies utilizing short periods of (14)C-bicarbonate fixation in young RS plants indicated that during the first 4 min most of the label was located in aspartic acid. These results are discussed in terms of previous results and particularly Cantino's hypothesis concerning the relationship between bicarbonate induction and tricarboxylic-cycle enzymes in the morphogenesis of B. emersonii.
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PMID:Tricarboxylic acid cycle enzymes and morphogenesis in Blastocladiella emersonii. 580 5

1. The effects of glyoxylate on partially purified preparations of aconitate hydratase, isocitrate dehydrogenase and oxoglutarate dehydrogenase were compared with those of oxalomalate and hydroxyoxoglutarate (obtained by condensation of glyoxylate with oxaloacetate and pyruvate respectively). 2. Glyoxylate (1mm) did not affect aconitate hydratase and isocitrate dehydrogenase, whereas oxalomalate (1mm) inhibited the enzyme activities completely. 3. Glyoxylate (0.025mm) inhibited oxoglutarate dehydrogenase irreversibly, whereas the same concentrations of oxalomalate and hydroxyoxoglutarate were ineffective. This inhibitory effect was prevented if oxoglutarate, pyruvate or oxaloacetate was mixed with the enzyme before the glyoxylate. 4. Incubation of oxoglutarate dehydrogenase with radioactive glyoxylate produced radioactive carbon dioxide; radioactivity was also recovered in the portion of the enzyme identified with thiamin pyrophosphate. 5. The behaviour of glyoxylate in producing multiple inhibitions of the citric acid cycle, either by direct interaction with oxoglutarate dehydrogenase, or by means of its condensation compounds which inhibit aconitate hydratase and isocitrate dehydrogenase, is discussed.
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PMID:Control of the citric acid cycle by glyoxylate. The mechanism of inhibition of oxoglutarate dehydrogenase, isocitrate dehydrogenase and aconitate hydratase. 582 Jun 38

1. Hydroxyoxoglutarate was obtained by three methods: decarboxylation of oxalomalic acid, and synthesis from glyoxylate and pyruvate by using either Mg(2+) or an enzyme from rat liver as catalysts. 2. The inhibitory effects of oxalomalate and hydroxyoxoglutarate upon aconitate hydratase, isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase were investigated. 3. Oxalomalate at low concentrations (1mm) inhibited almost completely both aconitate hydratase and isocitrate dehydrogenase. Hydroxyoxoglutarate also inhibited these enzymes, but at concentrations approximately tenfold that of oxalomalate. 4. Oxalomalate and hydroxyoxoglutarate, at the higher concentrations, inhibited oxoglutarate dehydrogenase to approximately the same extent. 5. It is suggested that the ability of glyoxylate to control reaction rates in the tricarboxylic acid cycle must in some degree be due to its condensation with oxaloacetate and pyruvate to form enzyme inhibitors.
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PMID:Control of the citric acid cycle by glyoxylate. Mechanism of the inhibition by oxalomalate and gamma-hydroxy-alpha-oxoglutarate. 603 57

Acetate oxidation by sulphate was studied with desulfobacter postgatei. Cell extracts of the organism were found to contain high activities of the following enzymes: citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase, malate dehydrogenase and pyruvate synthase. It is concluded that acetate oxidation with sulphate in D. postgatei proceeds via the citric acid cycle with the synthesis of pyruvate from acetyl CoA and CO2 as an anaplerotic reaction. The apparent Ks for acetate oxidation by D. postgatei as determined in vivo was near 0.2 mM. The apparent Ks for acetate fermentation to methane and CO2 by methanosarcina barkeri was 3 mM. The significantly lower ks for acetate of the sulphate reducer explains why methane formation from acetate in natural habitats is apparently inhibited by sulphate.
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PMID:Dissimilatory sulphate reduction with acetate as electron donor. 612 36

Metabolism of the glutamate group of amino acids--glutamic acid, gamma-amino-butyric acid, glutamine, aspartic acid and alanine--was studied in the brain of rat as a function of age. The levels of glutamic acid, glutamine and aspartic acid decreased while those of gamma-aminobutyric acid, and alanine increased with age. The results on the activity of the twelve enzymes involved in the metabolism showed that five of them (glutamate dehydrogenase, glutamine synthase, gamma-aminobutyric acid transaminase, succinic semialdehyde dehydrogenase and NAD+-isocitrate dehydrogenase) decreased, while four of them (glutaminase, glutamotransferase, glutamic acid decarboxylase, and alpha-ketoglutarate dehydrogenase) increased. The other three enzymes (aspartate aminotransferase, alanine aminotransferase and NADP+-isocitrate dehydrogenase) did not show any significant change in activity. An age-related increase was seen in alpha-ketoglutarate and ammonia, the intermediates involved in the metabolism of these amino acids. The changes in the level of these amino acids are discussed in relation to the altered energy metabolism during aging.
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PMID:Metabolism of the glutamate group of amino acids in rat brain as a function of age. 614 62

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

Adrenaline, noradrenaline, vasopressin and angiotensin increased 14CO2 production from [1-14C]oleate by hepatocytes from fed rats but not by hepatocytes from starved rats. The hormones did not increase 14CO2 production when hepatocytes from fed rats were depleted of glycogen in vitro. Increased 14CO2 production from ]1-14C]oleate in response to the hormones was observed when hepatocytes from starved rats were incubated with 3-mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase. 3-Mercaptopicolinate inhibited uptake and esterification of [1-14C]oleate, slightly increased 14CO2 production from [1-14C]oleate and greatly increased the [3-hydroxybutyrate]/[acetoacetate] ratio. In the presence of 3-mercaptopicolinate 14CO2 production in response to the catecholamines was blocked by the alpha-antagonist phentolamine and required extracellular Ca2+. The effects of vasopressin and angiotensin were also Ca2+-dependent. The actions of the hormones of 14CO2 production from [I-14C]oleate by hepatocytes from starved rats in the presence of 3-mercaptopicolinate thus have the characteristics of the response to the hormones found with hepatocytes from fed rats incubated without 3-mercaptopicolinate. The stimulatory effects of the hormones on 14CO2 production from [1-14C]oleate were not the result of decreased esterification (as the hormones increased esterification) or increased beta-oxidation. It is suggested that the effect of the hormones to increase 14CO2 production from [1-14C]oleate are mediated by CA2+-activation of NAD+-linked isocitrate dehydrogenase, the 2-oxoglutarate dehydrogenase complex, and/or electron transport. The results also demonstrate that when the supply of oxaloacetate is limited it is utilized for gluconeogenesis rather than to maintain tricarboxylic acid-cycle flux.
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PMID:Stimulation of [1-14C]oleate oxidation to 14CO2 in isolated rat hepatocytes by the catecholamines, vasopressin and angiotensin. A possible mechanism of action. 640 2

NADH:ubiquinone reductase (complex I) of the mitochondrial inner membrane respiratory chain binds a number of mitochondrial matrix NAD-linked dehydrogenases. These include pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase complex, mitochondrial malate dehydrogenase, and beta-hydroxyacyl-CoA dehydrogenase. No binding was detected between complex I and cytosolic malate dehydrogenase, glutamate dehydrogenase, NAD-isocitrate dehydrogenase, lipoamide dehydrogenase, citrate synthase, or fumarase. The dehydrogenases that bound to complex I did not bind to a preparation of complex II and III, nor did they bind to liposomes. The binding of pyruvate dehydrogenase complex, alpha-ketoglutarate dehydrogenase complex, and mitochondrial malate dehydrogenase to complex I is a saturable process. Based upon the amount of binding observed in these in vitro studies, there is enough inner membrane present in the mitochondria to bind the dehydrogenases in the matrix space. The possible metabolic significance of these interactions is discussed.
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PMID:Complex I binds several mitochondrial NAD-coupled dehydrogenases. 643 16


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