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)

Antibodies specific for the Mr 65,000 (flavoprotein) and the Mr 28,000 subunits of the succinic dehydrogenase (SDH) of Bacillus subtilis were obtained. By using these antibodies it was shown that both subunits accumulated in the cytoplasm during 5-aminolevulinic acid starvation of a 5-aminolevulinic acid auxotroph. In the cytoplasm the subunits were not associated since they precipitated essentially independently of each other with subunit-specific antibody. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis the cytoplasmic subunits migrated identically with the corresponding subunits from the purified membrane-bound SDH complex. Cytoplasmic subunits were pulse-labeled with L-[35S]methionine during 5-aminolevulinic acid starvation. The labeled subunits bound to the membrane when heme synthesis was resumed and also when protein synthesis was blocked by chloramphenicol before readdition of 5-aminolevulinic acid. The experiments thus demonstrated a precursor relationship between cytoplasmic subunits and the subunits of the membrane-bound SDH complex. All SDH-negative mutants isolated so far carry mutations in the citF locus. None of the mutants was found to have either the Mr 65,000 or the Mr 28,000 SDH subunits in the membrane. Four citF mutants, however, contained both subunits in the cytoplasm. Three of these mutants lacked spectrally detectable cytochrome b558. The respective mutations mapped at one end of the citF locus. These results strongly support our previous suggestion that cytochrome b558 is (part of) a membrane binding site for SDH in B. subtilis.
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PMID:Biosynthesis and membrane binding of succinate dehydrogenase in Bacillus subtilis. 677 71

The nucleotide sequence of the frdA gene, which encodes the flavoprotein subunit of the fumarate reductase, of Escherichia coli, has been determined. A polypeptide of Mr = 66,052, containing 602 amino acid residues, is predicted. In composition the FrdA protein strongly resembles the flavoprotein subunits of two succinate dehydrogenases. Moreover, a sequence of nine consecutive residues is common to the flavoprotein subunits from fumarate reductase and the beef heart succinate dehydrogenase. This sequence contains a histidyl residue which probably services as the site for attachment of the FAD cofactor to the reductase.
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PMID:Nucleotide sequence coding for the flavoprotein subunit of the fumarate reductase of Escherichia coli. 703 4

2-Month-old male Wistar rats were given sodium tetraborate in drinking water (3 g/l). Cerebral succinate dehydrogenase activity increased after 10 and 14 weeks of exposure. Increased RNA concentration and increased acid proteinase activity in brain occurred after 14 weeks. NADPH-cytochrome c reductase activity and cytochrome b5 content decreased in the liver microsomal fraction after 10 and 14 weeks. A reduction in the cytochrome P-450 concentration was detected at 14 weeks. The results support the hypothesis that borate anion exerts its toxic action by interfering with flavin metabolism in flavoprotein-dependent pathways.
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PMID:Effects of extended peroral borate ingestion on rat liver and brain. 708 88

The relative efficiencies of phenazine methosulfate (PMS), 1-methoxy-phenazine methosulfate (MPMS) and Meldola Blue (MB) as electron carriers were determined biochemically (non-enzymic NADH-tetrazolium salt-test) and by quantitative histochemistry (heart and kidney slices; succinate dehydrogenase, SDH; lactate dehydrogenase, LDH). MPMS developed the highest electron transfer velocity in biochemical assays. The reaction was independent of the pH value between 7.0-8.5. PMS and MB always showed a lower transfer ability in biochemical tests which was higher with iodonitrotetrazolium chloride (INT) than with nitro blue tetrazolium chloride (NBT). A distinct pH dependence was demonstrable with MB in this respect, preferentially using INT as tetrazolium salt. Quantitative histochemical results with electron carriers are often at variance with biochemical ones. MPMS leads to somewhat higher demonstrable activities only in the determination of the NAD-dependent LDH, whereas MB results in somewhat higher LDH activity than PMS (reaction medium with agarose). MB and PMS yielded almost equally high activities in the demonstration of the flavoprotein-dependent SDH using a reaction medium with agarose. With an aqueous reaction medium, PMS resulted in higher SDH activities than MB. MPMS always had the lowest efficiency in electron transfer ability using an aqueous or agarose containing reaction medium (SDH). With PVA in the reaction medium (SDH determination) PMS was clearly superior to MPMS. MB showed only a small transfer activity under these conditions because PVA seems to bind MB almost completely. It is concluded that in histochemistry an appropriate electron carrier and electron carrier concentration must be determined for different incubation conditions, tissues, tissue preparations and dehydrogenases studied. General statements about the efficiency or inefficiency of an electron carrier as a result of only one incubation condition does not seem to be justified.
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PMID:Quantitative dehydrogenase histochemistry with exogenous electron carriers (PMS, MPMS, MB). 711 85

We now report a mutation in the nuclear-encoded flavoprotein (Fp) subunit gene of the succinate dehydrogenase (SDH) in two siblings with complex II deficiency presenting as Leigh syndrome. Both patients were homozygous for an Arg554Trp substitution in the Fp subunit. Their parents (first cousins) were heterozygous for the mutation that occurred in a conserved domain of the protein and was absent from 120 controls. The deleterious effect of the Arg to Trp substitution on the catalytic activity of SDH was observed in a SDH- yeast strain transformed with mutant Fp cDNA. The Fp subunit gene is duplicated in the human genome (3q29; 5p15), with only the gene on chromosome 5 expressed in human-hamster somatic cell hybrids. This is the first report of a nuclear gene mutation causing a mitochondrial respiratory chain deficiency in humans.
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PMID:Mutation of a nuclear succinate dehydrogenase gene results in mitochondrial respiratory chain deficiency. 755 Mar 41

Mitochondrial complex II functions as a fumarate reductase (FRD), the reverse reaction of succinate dehydrogenase (SDH), and plays an important role in the anaerobic respiratory chain of parasitic helminths. In this study, complex II from the dog heartworm, Dirofilaria immitis adult, which is thought to act as a homolactatic fermenter, was examined in terms of its enzymatic features and primary structure in order to investigate the possible role of mitochondria in this filaria. Mitochondria from D. immitis adult showed high FRD activity when the enzymatic assay was performed using methylviologen as an artificial electron donor. The ratio of SDH to FRD in D. immitis was comparable to that in Ascaris suum adult, which is known to have an anaerobic mitochondrial respiratory chain with a high FRD activity of complex II. The FRD activity of D. immitis mitochondria was inhibited by the sulfhydryl reagent N-ethylmaleimide (NEM), while that of A. suum complex II was resistant to this inhibitor. The presence of the flavoprotein (Fp) subunit, which contains the substrate binding active site, was confirmed in D. immitis mitochondria by immunoblotting using a monoclonal antibody against the A. suum Fp subunit. By homology probing with the polymerase chain reaction, the entire cDNA for the D. immitis adult Fp was cloned and sequenced. The deduced amino acid sequence showed significant homology to that of A. suum and other mitochondrial Fps, in contrast to much less similarity to bacterial FRD, even though the D. immitis complex II showed high FRD activity. These results are the first indication of the presence of a functional complex II in D. immitis mitochondria.
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PMID:Comparative study and cDNA cloning of the flavoprotein subunit of mitochondrial complex II (succinate-ubiquinone oxidoreductase: fumarate reductase) from the dog heartworm, Dirofilaria immitis. 761 71

Complex II in adult mitochondria of the parasitic nematode, Ascaris suum, exhibits high fumarate reductase activity and plays a key role in the anaerobic electron-transport observed in these organelles. In the present study, cDNAs for the flavoprotein (Fp) subunits of complex II have been isolated, cloned and sequenced from both A. suum and the aerobic, free-living nematode, Caenorhabditis elegans. Additional sequence at the 3' end of the mRNAs was determined by the Rapid Amplification of cDNA Ends (RACE). Nucleotide sequence analysis of the A. suum cDNAs revealed a 22-nucleotide trans-spliced leader sequence characteristic of many nematode mRNAs, an open reading frame of 1935 nucleotides and a 3' untranslated region of 616 nucleotides including a poly (A) tail from a polyadenylation signal (AATAAA). The open reading frame encoded a 645 amino acid sequence, including a 30 amino acid mitochondrial presequence. The amino acid sequences for the Fp subunits from both organisms were very similar, even though the ascarid enzyme functions physiologically as a fumarate reductase and the C. elegans enzyme a succinate dehydrogenase. The ascarid sequence was much less similar to the Escherichia coli fumarate reductase. The sensitivity of other Fp subunits to sulfhydryl reagents appears to reside in a cysteine immediately preceding a conserved arginine in the putative active site. In both nematode sequences, this cysteine is replaced by serine even though the succinate dehydrogenase activity of both enzymes is still sensitive to sulfhydryl inhibition. A cysteine six residues upstream of the serine may be involved in the sulfhydryl sensitivity of the nematode enzymes. Surprisingly, in contrast to succinate dehydrogenase activity, the fumarate reductase activity of the ascarid enzyme was not sensitive to sulfhydryl inhibition, suggesting that the mechanism of the two reactions involves separate catalytic processes.
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PMID:Sequence comparison between the flavoprotein subunit of the fumarate reductase (complex II) of the anaerobic parasitic nematode, Ascaris suum and the succinate dehydrogenase of the aerobic, free-living nematode, Caenorhabditis elegans. 773 64

EPR spectroscopy was used to investigate the cytochrome P-450-dependent steroid hydroxylase ecdysone 20-mono-oxygenase of the cotton leafworm (Spodoptera littoralis) and the redox centres associated with membranes from the fat-body mitochondrial fraction. Intense features at g = 2.42, 2.25 and 1.92 from oxidized mitochondrial membranes have been assigned to the low-spin haem form of ferricytochrome P-450, probably of ecdysone 20-mono-oxygenase. High-spin cytochrome P-450 (substrate-bound) was tentatively assigned to a signal at g = 8.0, which was detectable from membranes as prepared. An EPR signal characteristic of a [2Fe-2S] cluster detected from the soluble mitochondrial matrix fraction has been shown to be distinct from the signals associated with mitochondrial NADH dehydrogenase and succinate dehydrogenase, and has therefore been attributed to a ferredoxin. We conclude that the S. littoralis fat-body mitochondrial electron-transport system involved in steroid 20-hydroxylation comprises both ferredoxin and cytochrome P-450 components, and thus resembles the enzyme systems of adrenocortical mitochondria. EPR signals characteristic of the respiratory chain were also observed from fat-body mitochondria and assigned to the iron-sulphur clusters associated with Complex I (Centres N1, N2), Complex II (Centres S1, S3), Complex III (the Rieske centre), and the copper centre of Complex IV, demonstrating similarities to mammalian mitochondria. The reduced membrane fraction also yielded a major resonance at g = 2.09 and 1.88 characteristic of the [4Fe-4S] cluster of electron-transferring flavoprotein: ubiquinone oxidoreductase. As the fat-body is the major metabolic organ of insects, this protein is presumably required for the beta-oxidation of fatty acids in mitochondria. High-spin haem signals in the low-field region of spectra also demonstrated that the mitochondrial fraction contains relatively high concentrations of catalase.
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PMID:EPR spectroscopic characterization of the iron-sulphur proteins and cytochrome P-450 in mitochondria from the insect Spodoptera littoralis (cotton leafworm). 774 2

Complex II (succinate-ubiquinone oxidoreductase) is an important enzyme complex in both the tricarboxylic acid cycle, and the aerobic respiratory chains of mitochondria in eukaryotic cells and prokaryotic organisms. In this study, homology probing with mixed primers for the polymerase chain reaction and subsequent sequence analysis were successfully applied to clone cDNA for the flavoprotein (Fp) subunit of human liver complex II. The isolated clone contains an open reading frame of 1,992 nucleotides and encodes a mature protein of 621 amino acids with a molecular weight of 68,011. The amino acid sequence was highly homologous with that of bovine heart Fp (93.2%) and was quite different from the partial sequence of human placental Fp reported previously [Malcovati et al. (1991) in Flavins and Flavoproteins 1990, pp. 727-730], which showed striking homology to that of Bacillus subtilis. To solve this discrepancy, the partial cDNA sequences of the stomach and placental Fp subunits of human complex II were determined in addition to the full length cDNA of liver. The sequence data, sensitivity to thiol reagents and antigenic properties indicated that the major from of FP subunit in human complex II is unique at least among the three tissues analyzed, and is more similar to the Fp subunit of bovine heart than to that of B. subtilis.
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PMID:Human complex II (succinate-ubiquinone oxidoreductase): cDNA cloning of the flavoprotein (Fp) subunit of liver mitochondria. 779 81

Complex II from mitochondria of the adult parasitic nematode, Ascaris suum, exhibits high fumarate reductase activity and plays a key role in the anaerobic electron transport observed in these organelles. In contrast, mitochondria isolated from free living second stage larvae (L2) of A. suum show much lower fumarate reductase activity than those from adults, whereas succinate dehydrogenase activities of mitochondria in both stages are comparable. In the present study, biochemical and antigenic properties of the partially purified enzymes from both larval and adult mitochondria were compared. Larval complex II eluted from the DEAE-Cellulofine column chromatography at a lower salt concentration than adult enzyme, whereas the apparent molecular size of both enzyme complexes estimated by gel permeation column chromatography was the same. The fumarate reductase activity of larval complex II was less than 3% of that of adult enzyme, and the Km values for substrates were significantly different between the two complexes. The flavoprotein subunit of larval complex II could be distinguished from that of adult complex II by two-dimensional gel electrophoresis and peptide mapping. The antibody against the smallest subunit (small subunit of cytochrome b558) of the adult enzyme did not cross-react with that of the larval enzyme. These results suggest that larval complex II differs from adult enzyme and is more similar to aerobic mammalian enzymes with low fumarate reductase activity. This is the first direct indication of the two different stage-specific forms of mitochondrial complex II.
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PMID:Stage-specific isoforms of complex II (succinate-ubiquinone oxidoreductase) in mitochondria from the parasitic nematode, Ascaris suum. 782 32


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