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:1.3.5.1 (succinate dehydrogenase)
8,177 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Young male Sprague-Dawley rats and Syrian hamsters were treated with 25-1000 mg/kg/day di-(2-ethylhexyl) phthalate (DEHP) orally for 14 days. Liver enlargement was observed in both species, the magnitude being greater in the rat than in the hamster. In the rat there was a marked dose-dependent induction of the peroxisomal marker cyanide-insensitive palmitoyl-CoA oxidation and also of carnitine acetyltransferase. Little effect was observed on the mitochondrial markers carnitine palmitoyltransferase and succinate dehydrogenase. Whereas in the rat, increased peroxisomal enzyme activities were observed after treatment with 100 and 250 mg/kg/day DEHP, much less effect was observed in the hamster even after 1000 mg/kg/day DEHP. Parallel morphological investigations demonstrated a greater increase in hepatic peroxisome numbers in the rat than in the hamster. 14C-labeled DEHP was found to be more rapidly hydrolyzed by rat than hamster hepatic and small intestinal mucosal cell preparations and differences were also observed in the absorption and excretion of oral doses of [14C]DEHP. Studies with mono-(2-ethylhexyl) phthalate (MEHP), a primary metabolite of DEHP, and a hypolipidemic drug clofibrate also resulted in a greater increase in hepatic peroxisomal enzymes in the rat compared to the hamster. The results demonstrate that while DEHP, MEHP, and clofibrate induced hepatic peroxisome proliferation in both species, there was a marked species difference in response. Comparative long-term studies in these species may thus help to clarify the role of peroxisome proliferation in the hepatocarcinogenicity of DEHP.
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PMID:Comparative studies on di-(2-ethylhexyl) phthalate-induced hepatic peroxisome proliferation in the rat and hamster. 671 Apr 84

We have developed methods for separating the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. The total membrane fraction from ethylenediaminetetraacetic acid-lysozyme-treated cells was resolved into three major fractions by isopycnic density centrifugation. Between 85 and 90% of the succinate dehydrogenase and cyanide-sensitive reduced nicotinamide adenine dinucleotide oxidase activity was found in the first (I) fraction (rho = 1.221 g/ml) and 80% of the membrane-associated 2-keto-3-deoxyoctonate was found in the third (III) fraction (rho = 1.166 g/ml). The middle (II) fraction (rho = 1.185 g/ml) appeared to be a hybrid membrane fraction and contained roughly 10 to 20% of the activity of the enzyme markers and 2-keto-3-deoxyoctonate. No significant amounts of deoxyribonucleic acid or ribonucleic acid were present in the three isolated fractions, although 26% of the total cellular deoxyribonucleic acid and 3% of the total ribonucleic acid were recovered with the total membrane fraction. Phosphatidylethanolamine made up the bulk (60 to 70%) of the phospholipids in the membrane fractions. However, virtually all of the phosphatidylserine and cardiolipin were found in fraction I. Fraction III appeared to contain elevated amounts of lysophospholipids and contained almost three times the amount of total phospholipid as compared with fraction I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved approximately 40 polypeptides in the total membrane fraction. Two-thirds of these polypeptides were enriched in fraction I, and the remainder was enriched in fraction III. Fraction II contained a banding pattern similar to the total membrane fraction. Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium. The atypically low bouyant density of the outer membrane of M. xanthus is discussed with regard to the high phospholipid content of the outer membrane.
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PMID:Separation and properties of the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. 676 94

Rat and pigeon heart mitochondria supplemented with antimycin produce 0.3-1.0nmol of H(2)O(2)/min per mg of protein. These rates are stimulated up to 13-fold by addition of protophores (carbonyl cyanide p-trifluoromethoxyphenylhydrazone, carbonyl cyanide m-chloromethoxyphenylhydrazone and pentachlorophenol). Ionophores, such as valinomycin and gramicidin, and Ca(2+) also markedly stimulated H(2)O(2) production by rat heart mitochondria. The enhancement of H(2)O(2) generation in antimycin-supplemented mitochondria and the increased O(2) uptake of the State 4-to-State 3 transition showed similar protophore, ionophore and Ca(2+) concentration dependencies. Thenoyltrifluoroacetone and N-bromosuccinimide, which inhibit succinate-ubiquinone reductase activity, also decreased mitochondrial H(2)O(2) production. Addition of cyanide to antimycin-supplemented beef heart submitochondrial particles inhibited the generation of O(2) (-), the precursor of mitochondrial H(2)O(2). This effect was parallel to the increase in cytochrome c reduction and it is interpreted as indicating the necessity of cytochrome c(1) (3+) to oxidize ubiquinol to ubisemiquinone, whose autoxidation yields O(2) (-). The effect of protophores, ionophores and Ca(2+) is analysed in relation to the propositions of a cyclic mechanism for the interaction of ubiquinone with succinate dehydrogenase and cytochromes b and c(1) [Wikstrom & Berden (1972) Biochim. Biophys. Acta283, 403-420; Mitchell (1976) J. Theor. Biol.62, 337-367]. A collapse in membrane potential, increasing the rate of ubisemiquinone formation and O(2) (-) production, is proposed as the molecular mechanism for the enhancement of H(2)O(2) formation rates observed on addition of protophores, ionophores and Ca(2+).
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PMID:Enhancement of hydrogen peroxide formation by protophores and ionophores in antimycin-supplemented mitochondria. 740 88

Within a few minutes after addition to L929 cells, tumour necrosis factor-alpha (TNF alpha) induced an increase in lucigenin-enhanced chemiluminescence that could be inhibited by superoxide dismutase. The generation of superoxide anion (O2.-) was sensitive to treatment with rotenone, antimycin A and cyanide, indicating that the signal originated from mitochondria. The mechanism of production of O2.- was shown to be independent of ATP synthesis, as uncoupling of this event from mitochondrial electron transport did not alter the generation of O2.- induced by TNF alpha. Chemiluminescence was further dependent on the presence of extracellular calcium, suggesting a role for this cation as a second messenger. This hypothesis was supported by the finding that inhibition of mitochondrial calcium uptake by Ruthenium Red exerted a protective effect on TNF alpha-treated L929 cells. Increased O2.- generation was followed by a marked decrease in mitochondrial dehydrogenase activity and cellular ATP levels, while cell membrane permeability was moderately increased. A role for mitochondrial O2.- generation in TNF alpha cytotoxicity was further supported by the finding that resistant L929 cells had decreased ability to produce O2.- in response to TNF alpha. In addition, we detected a decreased activity of the mitochondrial enzyme succinate dehydrogenase in these cells, suggesting that this component of the respiratory chain might be an important contributor to the TNF alpha-induced generation of O2.-.
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PMID:Tumour necrosis factor-alpha induces superoxide anion generation in mitochondria of L929 cells. 767 39

The carbohydrate metabolism of free-living and parasitic stages of the sheep nematode Haemonchus contortus was studied, and it was demonstrated that during development a switch occurred from Krebs-cycle activity towards a more fermentative metabolism. During this switch a transition might take place in complex II of the respiratory chain. In the free-living (L3) and early parasitic (XL3) stages, complex II catalyses the oxidation of succinate to fumarate via the Krebs cycle, whereas in adults complex II functions in the reverse reaction, the reduction of fumarate to succinate. L3 and XL3 were shown to already possess a large anaerobic capacity. They survived well in the absence of oxygen or in the presence of cyanide, which completely blocked respiration. Krebs-cycle activity, however, was only partially inhibited by cyanide; the XL3s in particular produced in the presence of cyanide large amounts of propanol, the production of which probably functions as an alternative electron sink. For further investigation of the observed metabolic switch, complex II of the respiratory chain, a key enzyme involved in this switch, was studied. The B subunit of complex II was cloned and sequenced. These clones all showed sequences similar to the B subunit of succinate dehydrogenase from other species, and included the amino-terminal signal sequence for importation into mitochondria. Two genes were identified, types 1 and 2, based on the DNA and amino acid sequences and on the lack of cross-reaction to each other when used as probes on Southern blots. On Northern blots, the two genes showed a different expression pattern during the development of the parasite.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential expression of two succinate dehydrogenase subunit-B genes and a transition in energy metabolism during the development of the parasitic nematode Haemonchus contortus. 780 77

The dependence of electron flux through quinone-reducing and quinol-oxidizing pathways on the redox state of the ubiquinone (Q) pool was investigated in plant mitochondria isolated from potato (Solanum tuberosum cv. Bintje, fresh tissue and callus), sweet potato (Ipomoea batatas) and Arum italicum. We have determined the redox state of the Q pool with two different methods, the Q-electrode and Q-extraction techniques. Although results from the two techniques agree well, in all tissues tested (with the exception of fresh potato) an inactive pool of QH2 was detected by the extraction technique that was not observed with the electrode. In potato callus mitochondria, an inactive Q pool was also found. An advantage of the extraction method is that it permits determination of the Q redox state in the presence of substances that interfere with the Q-electrode, such as benzohydroxamate and NADH. We have studied the relation between rate and Q redox state for both quinol-oxidizing and quinone-reducing pathways under a variety of metabolic conditions including state 3, state 4, in the presence of myxothiazol, and benzohydroxamate. Under state 4 conditions or in the presence of myxothiazol, a non-linear dependence of the rate of respiration on the Q-redox state was observed in potato callus mitochondria and in sweet potato mitochondria. The addition of benzohydroxamate, under state 4 conditions, removed this non-linearity confirming that it is due to activity of the cyanide-resistant pathway. The relation between rate and Q redox state for the external NADH dehydrogenase in potato callus mitochondria was found to differ from that of succinate dehydrogenase. It is suggested that the oxidation of cytoplasmic NADH in vivo uses the cyanide-resistant pathway more than the pathway involving the oxidation of succinate. A model is used to predict the kinetic behaviour of the respiratory network. It is shown that titrations with inhibitors of the alternative oxidase cannot be used to demonstrate a pure overflow function of the alternative oxidase.
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PMID:The relationship between electron flux and the redox poise of the quinone pool in plant mitochondria. Interplay between quinol-oxidizing and quinone-reducing pathways. 781 62

Ischemia/reperfusion mechanisms contribute to lung injury after transplantation, pulmonary embolism, and resolution of atelectasis. Alveolar tissue becomes hypoxic and deprived of substrate only when both ventilation and perfusion are interrupted, a situation modeled in vivo by complete, unilateral lung collapse. Because previously hypoxic mitochondria may be an important intracellular source of superoxide and hydrogen peroxide (H2O2) during reperfusion and re-oxygenation, the authors, in this study, investigated whether mitochondrial H2O2 release changed as a result of lung hypoxia/hypoperfusion resulting from collapse. Mitochondria were isolated from hypoxic (previously collapsed) right or contralateral left rabbits' lungs and from control rabbits' lungs. Mitochondrial H2O2 release, a marker of superoxide production, was measured fluorometrically after incubation with or without 1 mmol/L cyanide and 0.1 mmol/L nicotinamide adenine dinucleotide. Mitochondrial recovery was determined by assaying succinate dehydrogenase activity in mitochondrial preparations and lung homogenates. Lung succinate dehydrogenase activity and mitochondrial recovery were comparable among groups. Calculated lung mitochondrial content did not change (control subjects: left 7.9 +/- 0.5, right 13.8 +/- 1.7; hypoxic: left 10.3 +/- 1.3, right 10.5 +/- 2.4, all mg mitochondrial protein/lung). Mitochondria released hydrogen peroxide at approximately 5.6 nmol/h/mg pro in buffer alone and 14.8 nmol/h/mg pro in buffer with cyanide and nicotinamide adenine dinucleotide. However, lung collapse and resulting hypoxia caused no change in mitochondrial number or capacity to release H2O2 in vitro. Based on these findings, it is suggested that other sources of reactive oxygen metabolites, including xanthine oxidase and activated neutrophils, contribute to the oxidant injury observed in this model.
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PMID:Hydrogen peroxide release by mitochondria from normal and hypoxic lungs. 794 83

The respiratory chain of adult Paragonimus westermani, a lung fluke, was characterized in isolated mitochondria. The fluke mitochondria exhibited cyanide- and antimycin A-sensitive succinate oxidase activity at a rate of 16.8 nmol O2 min-1 mg-1 protein. The succinate oxidation was shown to be stimulated by ADP and linked to the formation of membrane potential. The specific activities of oxidoreductases composing the succinate oxidase system, i.e., succinate-ubiquinone and succinate--cytochrome c oxidoreductase (complex II and complex II-III, respectively) and cytochrome c oxidase (complex IV), were compared in mitochondria from adult Paragonimus, bovine heart (an aerobic tissue), and muscle of adult Ascaris suum which possesses an anaerobic respiratory chain. The activity values of complex II-III and complex IV were high, middle, and low for bovine heart, Paragonimus, and A. suum, respectively, whereas the activity of complex II was comparable among the three sources. The cytochrome contents of Paragonimus mitochondria as determined by difference absorption spectrophotometry ranged between those in Ascaris and bovine mitochondria for types c and aa3 cytochromes. Paragonimus mitochondria exhibited a high activity of NADH-fumarate reductase; the specific activity was about 18-fold higher in fluke submitochondria than in bovine heart submitochondria. Quinone analysis by HPLC and mass spectrometry showed that the fluke mitochondria contain both rhodoquinone-10 and ubiquinone-10 at concentrations of 0.572 and 0.321 nmol mg-1 mitochondrial protein, respectively. These data clearly show that mitochondria from adult P. westermani, unlike adult Ascaris mitochondria, possess both cyanide-sensitive succinate oxidase and NADH-fumarate reductase systems, indicating that the fluke mitochondria are facultatively anaerobic.
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PMID:Respiratory chain of the lung fluke Paragonimus westermani: facultative anaerobic mitochondria. 803 Nov 21

The kinetic modelling of the respiratory network in plant mitochondria is discussed, with emphasis on the importance of the choice of boundary conditions, and of modelling of both quinol-oxidising and quinone-reducing pathways. This allows quantitative understanding of the interplay between the different pathways, and of the functioning of the plant respiratory network in terms of the kinetic properties of its component parts. The effects of activation of especially succinate dehydrogenase and the cyanide-insensitive alternative oxidase are discussed. Phenomena, such as respiratory control ratios depending on the substrate, shortcomings of the Bahr and Bonner model for electron distribution between the oxidases and reversed respiratory control, are explained. The relation to metabolic control analysis of the respiratory network is discussed in terms of top-down analysis.
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PMID:Kinetic and regulatory aspects of the function of the alternative oxidase in plant respiration. 859 74

With an oxystat, changes in the pattern of expression of FNR-dependent genes from Escherichia coli were studied as a function of the O2 tension (pO2) in the medium. Expression of all four tested genes was decreased by increasing O2. However, the pO2 values that gave rise to half-maximal repression (pO(0.5)) were dependent on the particular promoter and varied between 1 and 5 millibars (1 bar = 10(5) Pa). The pO(0.5) value for the ArcA-regulated succinate dehydrogenase genes was in the same range (pO(0.5) = 4.6 millibars). At these pO2 values, the cytoplasm can be calculated to be well supplied with O2 by diffusion. Therefore, intracellular O2 could provide the signal to FNR, suggesting that there is no need for a signal transfer chain. Genetic inactivation of the enzymes and coenzymes of aerobic respiration had no or limited effects on the pO(0.5) of FNR-regulated genes. Thus, neither the components of aerobic respiration nor their redox state are the primary sites for O2 sensing, supporting the significance of intracellular O2. Non-redox-active, structural O2 analogs like CO, CN-, and N3-, could not mimic the effect of O2 on FNR-regulated genes under anaerobic conditions and did not decrease the inhibitory effect of O2 under aerobic conditions.
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PMID:O2 as the regulatory signal for FNR-dependent gene regulation in Escherichia coli. 875 79


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