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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)

Peroxisomes were isolated from the livers of both control and clofibrate-treated rats. Two procedures, one with a sucrose gradient, and a second with Percoll gradients, were utilized. The Percoll procedure allowed contamination of the isolated peroxisome fraction on protein basis, by lysosomes (8%), by mitochondria (5%) and by microsomes (2%). The peroxisome fraction isolated by the sucrose gradient showed no significant contamination with mitochondria, but the fraction contained 13% microsomes. In addition to established peroxisomal enzymes, the isolated peroxisomes also contained cytochrome b5, NADH-cytochrome c reductase and NADPH-isocitrate dehydrogenase. The peroxisomal membranes were also separated from the content, and they were found to have a relatively high phospholipid/protein ratio (0.55).
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PMID:Isolation of peroxisomes from rat liver using sucrose and Percoll gradients. 627 64

Escherichia coli was grown in chemostat culture under glycerol-limited and ammonium-limited conditions at growth rates between 0.1 and 0.5 h-1. At steady state, the concentrations of cyclic AMP and cyclic GMP and the activities of four constitutive enzymes (glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, NADH oxidase and cyclic phosphodiesterase) were determined in the organism. Addition of exogenous cyclic AMP, cyclic GMP or phencyclidine perturbed the steady state and caused inhibition or stimulation of synthesis of phosphodiesterase and isocitrate dehydrogenase. A novel hypothesis is proposed to account for the ability of bacteria to regulate the synthesis of constitutive enzymes with cyclic nucleotides and possibly other small molecules.
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PMID:Cyclic AMP and cyclic GMP control of synthesis of constitutive enzymes in Escherichia coli. 628 44

The utilization by yeast of two carbon sources is carried out through the operation of the glyoxylic acid cycle. Kinetic acid from the isocitrate transforming enzymes suggest that the flow of isocitrate through the glyoxylic acid cycle depends upon the inhibition of the isocitrate decarboxylating enzymes. Both isocitrate dehydrogenases are inhibited by a mixture of glyoxylate + oxaloacetate, but for the reasons described in the text we consider that this inhibition is of no physiological significance. On the other hand, we have found that NADPH is a competitive inhibitor of NADP-isocitrate dehydrogenase with respect to NADP+, with a KI similar to its KM. It also produces an additive effect on the NADH-produced inhibition of NAD-isocitrate dehydrogenase. We propose NADPH as the compound that channels the utilization of isocitrate into the glyoxylic acid cycle. This is supported by the finding of an increased NADPH/NADP+ ratio in acetate grown yeast with respect to glucose grown cells.
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PMID:NADPH/NADP+ ratio: regulatory implications in yeast glyoxylic acid cycle. 634 36

In porcine interareolar placental epithelia, the following enzymes were demonstrated by histochemical methods after 30, 58, 80, 100, and 110 d of pregnancy, respectively: beta-N-acetylhexosaminidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, acid phosphatase, alkaline phosphatase, nonspecific esterases, cytochrome oxidase, 5-nucleotidase, leucine aminopeptidase, adenosine triphosphatase, diaphorases (NADH, NADPH), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase (NAD, NADP), beta-hydroxybutyrate dehydrogenase, glycero-3-phosphate dehydrogenase, NAD-glycero-3-phosphate dehydrogenase, glutamate dehydrogenase (NAD, NADP), lactate dehydrogenase. The results show that most of the enzyme activities remained almost unchanged during the period of investigation. Only G-6-PDH and 6-PGDH activities increased within the uterine epithelium and nonspecific esterase activity within uterine as well as chorionic epithelia during the 2nd half of pregnancy. Within chorionic and uterine epithelia, hydrolases but not dehydrogenases demonstrated a higher activity at the bases of chorionic villi as compared to the apices and flanks of the latter. The action and influence of the demonstrated enzymes on metabolism, energy transfer, secretory, and resorptive activities of chorionic and uterine epithelia are discussed.
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PMID:[Enzyme histochemical studies of the swine placenta. Histoptics of enzymes in interareolar placental epithelia]. 643 35

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

A mathematical model is proposed to describe the interaction between glycolysis, the Krebs cycle and 3-oxidation (beta OX). The model incorporates the activations of phosphofructokinase by AMP and of isocitrate dehydrogenase by ADP as well as the inhibitions of citrate synthase by citrate, of acyl CoA synthase by excess CoAsAcyl, of pyruvate dehydrogenase (PDH) and the beta OX helix by the products CoAsAc and NADH. These regulations have been shown to provide consecutive triggering of the fatty acid and glucose oxidation systems with an increase in the ATPase load, the beta OX of fatty acids being a major source of energy at small loads. The steady state rates of glycolysis and PDH-reaction begin to increase at larger loads when the rate of beta OX is close to its maximum value. At maximum ATPase loads, the glucose oxidation accounts for more than 80% of the total energy production. Under limited fatty acid supply, the transfer to glucose oxidation gives rise to a region of the ATPase loads, where in the steady state levels of NADH and CoAsAc increase with load.
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PMID:[Ratio between carbohydrate and lipid metabolism in muscle cell energy metabolism during ATPase loading. Mathematical model]. 645 74

The activity of NAD-dependent isocitrate dehydrogenase from bovine heart was inhibited by NADH (apparent Ki about 4.3 microM) and NADPH (Ki about 9.8 microM) at subsaturating substrate concentrations at pH 7.4. The inhibition by NADH or NADPH was reversed competitively by magnesium isocitrate in the presence of ADP, but not without ADP. Reversal of inhibition by NADH or NADPH with respect to NAD+ was competitive or of the linear mixed type depending on whether ADP was absent or present. ADP3- (0.2 mM) increased the Ki(app) for NADPH from 9.8 to 27.1 microM; further addition of Ca2+ (0.2 mM) raised the Ki(app) to 127 microM. For the modification of NADPH inhibition by ADP, S0.5 for Ca2+ was approximately 48 microM. This compares to the Km for Ca2+ of 0.3-1 microM for the activation of the enzyme without NADPH [Denton, R. M., Richards, D. A., & Chin, J. G. (1978) Biochem. J. 176, 899-906; Aogaichi, T., Evans, J., Gabriel, J., & Plaut, G. W. E. (1980) Arch. Biochem. Biophys. 204, 350-360]. ADP did not affect the Ki for NADH. Magnesium citrate, which was about 100-fold more effective as a positive modifier of the enzyme with ADP than without ADP [Gabriel, J. L., & Plaut, G. W. E. (1983) Fed. Proc., Fed. Am. Soc. Exp. Biol. 42, 2082], reversed competitively the inhibition by NADPH in the presence of ADP, but not without ADP. Magnesium citrate did not reverse NADH inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of bovine heart NAD-specific isocitrate dehydrogenase by reduced pyridine nucleotides: modulation of inhibition by ADP, NAD+, Ca2+, citrate, and isocitrate. 646 15

Various enzymes of the tricarboxylic acid cycle (TCA) viz., aconitase (E.C. 4.2.1.3), isocitrate dehydrogenase (E.C. 1.1.1.42), succinate dehydrognease (E.C. 1.3.99.1), fumarate reductase (NADH: fumarate oxido-reductase), fumarase (E.C. 4.2.1.2) and maltate dehydrogenase (E.C. 1.1.1.37) were detected in adult Haemonchus contortus (Nematoda: Trichostrongylidae), in vitro. Low activities of aconitase and isocitrate dehydrogenase suggested that the TCA cycle has a minor function and the pathway of CO2 fixation is the major pathway in the energy metabolism of the parasite. In vitro incubation in Tyrode's solution had no significant effect on TCA cycle enzymes and the worm was able to maintain normal metabolism for 12 h. The effects of D L-tetramisole and rafoxanide on various enzymes of the TCA cycle were studied in adult H. contortus. At 50 micrograms ml-1 varying degrees of inhibition of succinate dehydrogenase and fumarate reductase activities were observed. At the same concentration, the activities of other enzymes remained unaltered.
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PMID:The effects of DL-tetramisole and rafoxanide on tricarboxylic acid cycle enzymes of Haemonchus contortus, in vitro. 668 86

The activity of NAD-linked alpha-glycerol-3-phosphate dehydrogenase (NAD-G3PDH; EC 1.1.1.8) was depressed by 35% when the thyroid hormone 3,3',5-triiodo-L-thyronine (20 micrograms/liter) was added to the serum-free, hormonally supplemented medium of cultured neonatal rat heart cells. The degree of depression was greater (65%) when the medium contained normal serum levels of hydrocortisone and insulin. There is a dramatic inverse dose-response relationship between triiodothyronine levels and NAD-G3PDH activity. The classic elevation by thyroid hormones of the FAD-linked alpha-glycerol-3-phosphate dehydrogenase (FAD-G3PD; EC 1.1.99.5) was observed concurrently. The medium-glucose depletion rate in triiodothyronine-free cells was depressed 32% through 11 days-in-culture, indicating reduced glycolytic activity. The activities of nine other metabolically important enzymes which were measured during this study, including hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphofructokinase, pyruvate kinase, malate dehydrogenase, NAD-isocitrate dehydrogenase, NADH cytochrome c reductase, and succinic cytochrome c reductase, did not respond to varying triiodothyronine concentrations.
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PMID:Triiodothyronine depresses the NAD-linked glycerol-3-phosphate dehydrogenase activity of cultured neonatal rat heart cells. 669 42

Adipose tissue from fetuses decapitated at 45 d of gestation was removed and structurally and histochemically analyzed at 65, 85 and 110 d of gestation. Subcutaneous adipose tissue from decapitated and control fetuses at 65 d of gestation was histologically and histochemically similar. A reduced number of fat cell clusters in the outer layer of subcutaneous tissue and a poorly developed dermis was evident in decapitated fetuses at 85 d of gestation. Fat cell size was similar for control and decapitated fetuses at 65 d of gestation, whereas cells in 85 d-old decapitated fetuses were larger than cells in control fetuses. Adipocytes from control and 85 d-old decapitated fetuses were histochemically similar except for an elevated number of esterase positive cells in decapitated fetuses. At 110 d of gestation, adipocytes from decapitated fetuses had higher activities of the following enzymes than did control adipocytes: malate dehydrogenase (NADP dependent) glucose 6-phosphate dehydrogenase NADP dependent), isocitrate dehydrogenase (NADP dependent), alpha-glycerol phosphate dehydrogenase (NADP dependent), NADPH-tetrazoleum reductase and esterase. Levels of succinate dehydrogenase, glutamate dehydrogenase and NADH-tetrazoleum reductase were similar in cells from controls and decapitated fetuses. These data indicate that fetal decapitation probably exerts a positive influence on enzymes involved in lipid synthesis. However, fetal decapitation also exerts a negative influence on fat cell hyperplasia.
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PMID:Histochemical and cellular aspects of adipose tissue development in decapitated pig fetuses: an ontogeny study. 674 43


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