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)

A simple system for aerobic assay of the quinol-fumarate reductase reaction catalyzed by purified soluble bovine heart succinate-ubiquinone reductase in the presence of NADH, NAD(P)H-quinone reductase (DT-diaphorase) and an appropriate quinone is described. The reaction is inhibited by carboxin, suggesting that the same quinone/quinol binding site is involved in electron transfer from succinate to ubiquinone and from ubiquinol to fumarate. The kinetic properties of the reaction in both directions and comparative affinities of the substrate binding sites of the enzyme to substrates (products) and competitive inhibitors are reported. Considerable difference in affinity of the substrates binding site to oxaloacetate was demonstrated when the enzyme was assayed in the direct and reverse directions. These results were taken to indicate that the oxidized dicarboxylate-free enzyme is an intermediate during the steady-state succinate-ubiquinone reductase reaction, whereas the reduced dicarboxylate-free enzyme is an intermediate of the steady-state ubiquinol-fumarate reductase reaction. No difference in the reactivity of the substrate-protected cysteine and arginine residues was found when the pseudo-first-order rate constants for N-ethylmaleimide and phenylglyoxal inhibition were determined for oxidized and quinol-reduced enzyme. Quinol-fumarate reductase activity was reconstituted from the soluble succinate dehydrogenase and low-molecular-mass ubiquinone reactivity conferring protein(s). No reduction of cytochrome b was observed in the presence of quinol generating system, whereas S-3 low temperature EPR-detectable iron-sulfur center was completely reduced by quinol under equilibrium (without fumarate) or steady-state (in the presence of fumarate). No significant reduction of ferredoxin type iron-sulfur centers was detected during the steady-state quinol-fumarate oxidoreductase reaction. The data obtained eliminate participation of cytochrome b in the quinol-fumarate reductase reaction and show that the rate limiting step of the overall reaction lies between iron-sulfur center S-3 and lower midpoint potential redox components of the enzyme.
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PMID:Fumarate reductase activity of bovine heart succinate-ubiquinone reductase. New assay system and overall properties of the reaction. 841 79

The Ascaris larval respiratory chain, particularly complex II (succinate-ubiquinone oxidoreductase), was characterized in isolated mitochondria. Low-temperature difference spectra showed the presence of substrate-reducible cytochromes aa3 of complex IV, c+c1 and b of complex III (ubiquinol-cytochrome c oxidoreductase) in mitochondria from second-stage larvae (L2 mitochondria). Quinone analysis by high-performance liquid chromatography showed that, unlike adult mitochondria, which contain only rhodoquinone-9, L2 mitochondria contain ubiquinone-9 as a major component. Complex II in L2 mitochondria was kinetically different from that in adult mitochondria. The individual oxidoreductase activities comprising succinate oxidase, and fumarate reductase were determined in mitochondria from L2 larvae, from larvae cultured to later stages, and from adult nematodes. The L2 mitochondria exhibited the highest specific activity of cytochrome c oxidase, indicating that L2 larvae have the most aerobic respiratory chain among the stages studied. The Cybs subunit of complex II in L2 and cultured-larvae mitochondria exhibited different reactivities against anti-adult Cybs antibodies. Taken together, these results indicate that the complex II of larvae is different from its adult counterpart. In parallel with this change in mitochondrial biogenesis, biosynthetic conversion of quinones occurs during development in Ascaris nematodes.
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PMID:Developmental changes in the respiratory chain of Ascaris mitochondria. 843 36

An active respiratory complex II (succinate:quinone oxidoreductase) has been purified from tetraether lipid membranes of the thermoacidophilic archaeon, Sulfolobus sp. strain 7. It consists of four different subunits with apparent molecular masses of 66, 37, 33, and 12 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 66-kDa subunit contains a covalently bound flavin, the 37-kDa subunit is a possible iron-sulfur protein carrying three distinct types of EPR-visible FeS cluster, and the 33- and 12-kDa subunits are putative membrane-anchor subunits, respectively. While no heme group is detected in the purified complex II, it catalyzes succinate-dependent reduction of ubiquinone-1 and 2,6-dichlorophenolindophenol in the absence of phenazine methosulfate. The respiratory complex II of Sulfolobus sp. strain 7 appears to be novel in that it functions as a true succinate:caldariellaquinone oxidoreductase, although inherently lacking any heme group. This further indicates that the heme group of several respiratory complexes II may not be involved in the redox intermediates of the electron transfer from succinate to quinone.
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PMID:Resolution of the aerobic respiratory system of the thermoacidophilic archaeon, Sulfolobus sp. strain 7. III. The archaeal novel respiratory complex II (succinate:caldariellaquinone oxidoreductase complex) inherently lacks heme group. 853 44

Many anaerobically functioning eukaryotes have an anaerobic energy metabolism in which fumarate is reduced to succinate. This reduction of fumarate is the opposite reaction to succinate oxidation catalyzed by succinate-ubiquinone oxidoreductase, complex II of the aerobic respiratory chain. Prokaryotes are known to contain two distinct enzyme complexes and distinct quinones, menaquinone and ubiquinone (Q), for the reduction of fumarate and the oxidation of succinate, respectively. Parasitic helminths are also known to contain two different quinones, Q and rhodoquinone (RQ). This report demonstrates that RQ was present in all examined eukaryotes that reduce fumarate during anoxia, not only in parasitic helminths, but also in freshwater snails, mussels, lugworms, and oysters. It was shown that the measured RQ/Q ratio correlated with the importance of fumarate reduction in vivo. This is the first demonstration of the role of RQ in eukaryotes, other than parasitic helminths. Furthermore, throughout the development of the liver fluke Fasciola hepatica, a strong correlation was found between the quinone composition and the type of metabolism: the amount of Q was correlated with the use of the aerobic respiratory chain, and the amount of RQ with the use of fumarate reduction. It can be concluded that RQ is an essential component for fumarate reduction in eukaryotes, in contrast to prokaryotes, which use menaquinone in this process. Analyses of enzyme kinetics, as well as the known differences in primary structures of prokaryotic and eukaryotic complexes that reduce fumarate, support the idea that fumarate-reducing eukaryotes possess an enzyme complex for the reduction of fumarate, structurally related to the succinate dehydrogenase-type complex II, but with the functional characteristics of the prokaryotic fumarate reductases.
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PMID:Rhodoquinone and complex II of the electron transport chain in anaerobically functioning eukaryotes. 853 65

Complex II (succinate-ubiquinone oxidoreductase) from Escherichia coli is composed of four nonidentical subunits encoded by the sdhCDAB operon. Gene products of sdhC and sdhD are small hydrophobic subunits that anchor the hydrophilic catalytic subunits (flavoprotein and iron-sulfur protein) to the cytoplasmic membrane and are believed to be the components of cytochrome b556 in E. coli complex II. In the present study, to elucidate the role of two hydrophobic subunits in the heme b ligation and functional assembly of complex II, plasmids carrying portions of the sdh gene were constructed and introduced into E. coli MK3, which lacks succinate dehydrogenase and fumarate reductase activities. The expression of polypeptides with molecular masses of about 19 and 17 kDa was observed when sdhC and sdhD were introduced into MK3, respectively, indicating that sdhC encodes the large subunit (cybL) and sdhD the small subunit (cybS) of cytochrome b556. An increase in cytochrome b content was found in the membrane when sdhD was introduced, while the cytochrome b content did not change when sdhC was introduced. However, the cytochrome b expressed by the plasmid carrying sdhD differed from cytochrome b556 in its CO reactivity and red shift of the alpha absorption peak to 557.5 nm at 77 K. Neither hydrophobic subunit was able to bind the catalytic portion to the membrane, and only succinate dehydrogenase activity, not succinate-ubiquinone oxidoreductase activity, was found in the cytoplasmic fractions of the cells. In contrast, significantly higher amounts of cytochrome b556 were expressed in the membrane when sdhC and sdhD genes were both present, and the catalytic portion was found to be localized in the membrane with succinate-ubiquitnone oxidoreductase and succinate oxidase activities. These results strongly suggest that both hydrophobic subunits are required for heme insertion into cytochrome b556 and are essential for the functional assembly of E. coli complex II in the membrane. Accumulation of the catalytic portion in the cytoplasm was found when sdhCDAB was introduced into a heme synthesis mutant, suggesting the importance of heme in the assembly of E. coli complex II.
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PMID:Two hydrophobic subunits are essential for the heme b ligation and functional assembly of complex II (succinate-ubiquinone oxidoreductase) from Escherichia coli. 855 Jun 13

Succinate:quinone oxidoreductase (EC 1.3.5.1) was first purified from the facultative alkaliphilic Bacillus sp. strain YN-2000 in the presence of Triton X-100. The isolated enzyme showed high succinate-ubiquinone oxidoreductase activity at pH 8.5. The Km for ubiquinone 1 and the Vmax of the enzyme were determined to be about 5 microM and 48 micromol of ubiquinone 1 per min per mg, respectively. The catalytic activity of the enzyme was 50% inhibited by 9 microM 2-thenoyltrifluoroacetone or 0.8 microM 2-n-heptyl-4-hydroxyquinoline- N-oxide. The enzyme consisted of three kinds of subunits with molecular masses of 66, 26, and 15 kDa, respectively, and contained 1.28 mol of covalently bound flavin adenine dinucleotide, 0.9 mol of heme b, 1.35 mol of menaquinone, 8.3 mol of nonheme iron, and 7.5 mol of inorganic sulfide per mol of enzyme. The enzyme showed symmetrical alpha absorption peaks at 556.5 and 554 nm in the reduced state at room temperature and 77 K, respectively. The potentiometric analysis of the enzyme yielded an Em,7 of heme b of about -64 mV (n = 1). Furthermore, the content of the enzyme was increased up to fivefold when the bacterium was grown at pH 10 compared with pH 7. These results indicate that the succinate:quinone oxidoreductase with a single heme b is involved in the respiratory chain of the alkaliphile at a very alkaline pH.
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PMID:Succinate:quinone oxidoreductase (complex II) containing a single heme b in facultative alkaliphilic Bacillus sp. strain YN-2000. 865 76

The structural and catalytic properties of beef heart succinate dehydrogenase (succinate-ubiquinone oxidoreductase, complex II) and Escherichia coli fumarate reductase are remarkably similar. One exception is that whereas electron exchange between the mammalian enzyme and its quinone pool is inhibited by thenoyltrifluoroacetone and carboxanilides, the enzyme from E. coli is not sensitive to these inhibitors. The lack of good inhibitors has seriously hampered the elucidation of the mechanism of quinone oxidation/reduction in the E. coli enzyme. We have previously reported (Tan, A. K., Ramsay, R. R., Singer, T. P., and Miyoshi, H. (1993) J. Biol. Chem. 268, 19328-19333) that 2-alkyl-4,6-dinitrophenols inhibit mammalian complexes I, II, and III, but with different potencies and kinetic characteristics. Based on these studies we have selected a series of 2-alkyl-4,6-dinitrophenols which proved to be very effective noncompetitive inhibitors of mammalian complex II, particularly when acting in the direction of quinone reduction, the physiological event. These compounds turned out to be even more potent inhibitors of E. coli fumarate reductase, particularly when acting in the direction of quinol oxidation, again, the physiological event. Kinetic analysis revealed that with both enzymes 2 inhibitor binding sites seem to be involved in the oxidation of succinate by quinone, but one seems to be functioning when fumarate is reduced by external quinol. Since the E. coli enzyme can be modified by site-directed mutagenesis, these studies were extended to four mutants of fumarate reductase, impaired by single amino acid substitutions at either of the putative quinone binding sites (QA or QB) of the enzyme. The results were analyzed in terms of the model of these dual sites of quinone binding in fumarate reductase, as well as the nature of the substituent in the 2-position of the dinitrophenol inhibitors.
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PMID:Inhibitor probes of the quinone binding sites of mammalian complex II and Escherichia coli fumarate reductase. 870 65

The aim of the present study was to evaluate if defects of the respiratory chain known to occur in humans, also exist in lower primates. Cytochemical-immunocytochemical studies of the respiratory chain enzymes in five monkeys (10-25 years of age) showed defects of ubiquinone cytochrome-c-oxidoreductase (complex III), of cytochrome-c-oxidase (complex IV) and of ATP-synthase (complex V) in the limb muscles, diaphragm, heart muscle and extraocular muscles of three old animals (about 25 years) and also in the heart muscle of two younger animals (10 and 15 years). Characteristically, the defects were randomly distributed and there was no loss of succinate-dehydrogenase (complex II) in the fibres. Ultracytochemistry-immunocytochemistry of complex IV disclosed that in an involved fibre segment all the mitochondria exhibited the defect. The highest number of defects was observed in the extraocular muscle (up to 340/cm2) while the lowest defect density was present in the limb muscles (2-5/cm2). Defects of complex IV occurred two to three times more often than defects of complex III and besides isolated defects of complex III and IV, combined defects of both complexes were also observed. Defects of complex V occurred exclusively in combination and were rarely seen. Using subunit specific antisera against complex IV, it could be demonstrated at light and electron microscopic level that loss of activity of cytochrome-c-oxidase was associated with a loss both of mitochondrially and nuclearly coded subunits of the enzyme. In summary, aging in lower primates and humans is characterised by a highly similar defect expression of the respiratory chain enzymes, with intercellular and interorgan differences of the aging process, underlining the universal nature of the involved pathogenetic mechanisms.
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PMID:Defects of the respiratory chain in various tissues of old monkeys: a cytochemical-immunocytochemical study. 873 13

We studied two diagnostic aspects of fatal infantile defects of the mitochondrial respiratory chain: the age dependence of muscle mitochondrial enzyme activities and the reliability of diagnosis from autopsy samples. In morphologically normal quadriceps muscle samples of 46 children between the ages of 3 days and 15 years, activities of complex I plus III (NADH:cytochrome c oxidoreductase) and complex II plus III (succinate:cytochrome c oxidoreductase) increased 2-fold during the first three years of life, while that of complex II (succinate dehydrogenase), complex IV (cytochrome c oxidase), and citrate synthase did not show significant correlation with age. We suggest that these changes are related to age and stress the importance of strictly age-matched controls when diagnosing a mitochondrial disease of early childhood. The value of autopsy samples in diagnostic studies was evaluated by comparing mitochondrial enzyme activities in quadriceps muscle from autopsies and from surgical biopsies. In quadriceps muscle mitochondria, all the enzyme activities studied remained stable for at least 3 h after death. Using age-matched controls and autopsy samples, we diagnosed a respiratory chain enzyme deficiency in two infants, and the defects were confirmed in cultured skin fibroblasts.
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PMID:Diagnosis of fatal infantile defects of the mitochondrial respiratory chain: age dependence and postmortem analysis of enzyme activities. 874 50

In this study, we compared metronidazole (Mtz)-sensitive and -resistant strains of Helicobacter pylori for metabolic differences that might correlate with drug resistance. Included in this study was an isogenic Mtz(r) strain, HP1107, that was constructed by transforming genomic DNA from Mtz(r) strain HP439 into Mtz(s) strain HP500. Enzyme activities were also measured for Mtz(r) strains grown in the presence or absence of 18 micrograms of metronidazole per ml (ca. one-half of the MIC). These studies confirmed the presence of the Embden-Meyerhof-Parnas, Entner-Doudoroff, and pentose pathways. H. pylori strains expressed enzymatic activities indicative of a complete and active Krebs cycle. All strains expressed pyruvate oxidoreductase (POR) and alpha-ketoglutarate oxidoreductase (KOR) as measured with the redox-active dye benzyl viologen (30 to 96 nmol/min/mg of protein for POR and 30 nmol/min/mg of protein for KOR). When grown in the presence of Mtz at > or = 3.5 micrograms/ml, Mtz(r) strains expressed no detectable POR or KOR activity. The apparent repression of POR and KOR activities by Mtz affected bacterial growth as manifest by extended lag periods and growth yield reductions of > 30%. A dose-dependent relationship was demonstrated between the metronidazole concentration in the growth medium and the specific activity of POR measured in bacterial cell extracts. The observed repression was not due to inactivation of POR by Mtz. In addition to repression of POR and KOR activities, growth in the presence of Mtz also led to decreases in the activities of various Krebs cycle enzymes, including aconitase, isocitrate dehydrogenase and succinate dehydrogenase. All of the Mtz(r) strains examined expressed isocitrate lyase and malate synthase activities indicative of the glyoxylate bypass. No isocitrate lyase activity was detected in Mtz(s) strain HP500. Isocitrate lyase activity was expressed by HP500 following transformation to Mtz resistance (Mtz(r) strain HP1107) with DNA from an Mtz(r) strain. The results of this study suggest that Mtz resistance may be a recessive trait, possibly involving inactivation of a regulatory gene, that results in constitutive expression of isocitrate lyase. Repression of POR and KOR activities in response to low levels of Mtz may be a general response of H. pylori strains to Mtz, but only resistant strains manage to survive via activation of compensatory metabolic pathways.
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PMID:Metabolic activities of metronidazole-sensitive and -resistant strains of Helicobacter pylori: repression of pyruvate oxidoreductase and expression of isocitrate lyase activity correlate with resistance. 875 44


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