Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In isolated plant mitochondria the oxidation of both succinate and exogenous NADH responded in the expected manner to the addition of ADP or uncoupling agents, and the uncoupled rate of respiration was often in excess of the rate obtained in the presence of ADP. However, the oxidation of NAD+-linked substrates responded in a much more complex manner to the addition of ADP or uncoupling agents such as carbonyl cyanide p-trifluoromethoxyphenylhydrazone to mitochondria oxidizing pyruvate plus malate failed to result in a reliable stimulation; this uncoupled rate could be stimulated by adding AMP or ADP in the presence of oligomycin or bongkrekic acid. Spectrophometric measurements showed that the addition of AMP or ADP resulted in the simultaneous oxidation of endogenous nicotinamide nucleotide and the reduction of cytochrome b. ADP was only effective in bringing about these changes in redox state in the presence of Mg2+ whereas AMP did not require Mg2+. It was concluded that AMP activated the flow of electrons from endogenous nicotinamide nucleotide to cytochrome b, possible at the level of the internal NADH dehydrogenase.
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PMID:The activation of non-phosphorylating electron transport by adenine nucleotides in Jerusalem-artichoke (Helianthus tuberosus) mitochondria. 122 6

The reduction of duroquinone (DQ) and 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB) by NADH and ethanol was investigated in intact yeast mitochondria with good respiratory control ratios. In these mitochondria, exogenous NADH is oxidized by the NADH dehydrogenase localized on the outer surface of the inner membrane, whereas the NADH produced by ethanol oxidation in the mitochondrial matrix is oxidized by the NADH dehydrogenase localized on the inner surface of the inner membrane. The reduction of DQ by ethanol was inhibited 86% by myxothiazol; however, the reduction of DQ by NADH was inhibited 18% by myxothiazol, suggesting that protein-protein interactions between the internal (but not the external) NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase (the cytochrome bc1 complex) are involved in the reduction of DQ by NADH. The reduction of DQ and DB by NADH and ethanol was also investigated in mutants of yeast lacking cytochrome b, the iron-sulfur protein, and ubiquinone. The reduction of both quinone analogues by exogenous NADH was reduced to levels that were 10 to 20% of those observed in wild-type mitochondria; however, the rate of their reduction by ethanol in the mutants was equal to or greater than that observed in the wild-type mitochondria. Furthermore, the reduction of DQ in the cytochrome b and iron-sulfur protein lacking mitochondria was myxothiazol sensitive, suggesting that neither of these proteins is an essential binding site for myxothiazol. The mitochondria from the three mutants also contained significant amounts of antimycin- and myxothiazol-insensitive NADH:cytochrome c reductase activity, but had no detectable succinate:cytochrome c reductase activity. These results suggest that the mutants lacking a functional cytochrome bc1 complex have adapted to oxidize NADH.
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PMID:Direct interaction between the internal NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase in the reduction of exogenous quinones by yeast mitochondria. 130 74

We report here some unusual properties of ubiquinol: cytochrome c reductase of eel and other fish mitochondria. The turnover rate of the reductase is clearly higher than in mammalian mitochondria and the binding constant for ubiquinone seems to be larger than in other vertebrates. Additionally, the reductase activity of fish mitochondria is resistant to some powerful inhibitors that bind to cytochrome b, in particular to funiculosin. After sequencing most of the gene of eel cytochrome b and comparing the deduced amino acid sequence with that of other fish and animals, we hypothesize that the decreased binding of funiculosin could be due to a few amino acid replacements in the third and fourth transmembrane helix of the protein. In particular, the presence of methionine instead of alanine at position 125 seems to be largely responsible for the strong resistance to funiculosin and also to the partial resistance to myxothiazol in all fish mitochondria. Correlations between some residue substitutions in cytochrome b and the different effects of funiculosin in different species are also considered.
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PMID:Cytochrome b of fish mitochondria is strongly resistant to funiculosin, a powerful inhibitor of respiration. 131 3

By use of restriction fragment length polymorphism analysis, we examined the liver mitochondrial DNA amplified by polymerase chain reaction from 60 Chinese subjects of 31 to 78 years of age. We found nine specific mtDNA polymorphisms that had never been reported before. Eleven subjects had an Alu I polymorphic site in the subunit 2 gene of NADH dehydrogenase, five had a Hae III polymorphic site in the cytochrome oxidase subunit 2 gene, and five had a Hinf I polymorphic site in the subunit 3 gene of cytochrome oxidase. No polymorphic site was found in the structural genes coding for subunits 1, 3, 4, 4L and 6 of NADH dehydrogenase, cytochrome b, and subunit 8 of ATP synthase. Detailed analysis of the RFLP data did not show age-dependent mtDNA polymorphisms. In addition, the analysis of the restriction patterns of all the mtDNAs revealed 12 mtDNA haplotypes in all the Chinese subjects examined. Among them, type 1 mtDNA was found to be the most predominant and comprised 63.3% of the total study subjects. The restriction patterns of type 1 mtDNA generated by all restriction enzymes were identical to those deduced from the Cambridge sequence of human mtDNA. About 8.3% of the subjects exhibited type 2 mtDNA, and 5% had types 3, 5 and 8 mtDNA, respectively. Each of the rest seven mtDNA types comprised about 2% of the samples. Moreover, type 1 mtDNA was found in the platelets of three white Americans. These findings suggest that type 2 to type 12 mtDNAs have come into existence through the generation or loss of specific polymorphic restriction sites in the mtDNA of the Chinese.
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PMID:Specific restriction fragment length polymorphism in liver mitochondrial DNA of the Chinese. 135 20

RNA editing of several mitochondrial transcripts in Trypanosoma brucei is developmentally regulated. The cytochrome b and cytochrome oxidase II mRNAs are edited in procyclic-form parasites but are primarily unedited in bloodstream forms. The latter forms lack the mitochondrial respiratory system present in procyclic forms. Editing of the NADH dehydrogenase 7 (ND7) and ND8 transcripts is also developmentally regulated but occurs preferentially in bloodstream forms. Other transcripts, cytochrome oxidase III and ATPase 6, are edited in both life forms. We have identified many minicircle-encoded guide RNAs (gRNAs) for ATPase 6, ND7, and ND8. The characteristics of these gRNAs reveal how extensively edited RNA can be edited in the 3'-to-5' direction. Northern (RNA) blot and primer extension analyses indicate that gRNAs for transcripts whose editing is developmentally regulated are present in both procyclic and bloodstream form parasites. These results suggest that the developmental regulation of editing in these transcripts is not controlled by the presence or absence of gRNAs.
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PMID:Guide RNAs for transcripts with developmentally regulated RNA editing are present in both life cycle stages of Trypanosoma brucei. 137 4

In the human gastrointestinal epithelium, in situ hybridisation demonstrates that 12 S and 16 S mitochondrial ribosomal RNAs show maximal steady-state levels on the surface epithelial cells of the normal small intestine and colon. The mitochondrial mRNAs, cytochrome b and NADH dehydrogenase (IV) have a uniform distribution throughout the crypt and surface (villus) epithelial cells of the small intestine and colon. Histochemical stains for the activity of the mitochondrial respiratory chain enzymes succinate dehydrogenase and cytochrome oxidase also show almost uniform activities throughout the crypt-surface epithelial cell axis in the small and large intestines. In sections of normal human oesophagus the levels of mitochondrial ribosomal RNAs, mitochondrial mRNAs and the activities of mitochondrial respiratory chain enzymes are maximal over the basal cells of the stratified squamous epithelium. These results show a relative increase in mitochondrial ribosomal RNA expression compared with mitochondrial mRNAs in surface cells of simple intestinal epithelia.
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PMID:Mitochondrial gene expression in the human gastrointestinal tract. 138 44

The sequence of 13.9 kilobases (kb) of the 17.1-kb mitochondrial genome of Mytilus edulis has been determined, and the arrangement of all genes has been deduced. Mytilus mitochondrial DNA (mtDNA) contains 37 genes, all of which are transcribed from the same DNA strand. The gene content of Mytilus is typically metazoan in that it includes genes for large and small ribosomal RNAs, for a complete set of transfer RNAs and for 12 proteins. The protein genes encode the cytochrome b apoenzyme, cytochrome c oxidase (CO) subunits I-III, NADH dehydrogenase (ND) subunits 1-6 and 4L, and ATP synthetase (ATPase) subunit 6. No gene for ATPase subunit 8 could be found. The reading frames for the ND1, COI, and COIII genes contain long extensions relative to those genes in other metazoan mtDNAs. There are 23 tRNA genes, one more than previously found in any metazoan mtDNA. The additional tRNA appears to specify methionine, making Mytilus mtDNA unique in having two tRNA(Met) genes. Five lengthy unassigned intergenic sequences are present, four of which vary in length from 79 to 119 nucleotides and the largest of which is 1.2 kb. The base compositions of these are unremarkable and do not differ significantly from that of the remainder of the mtDNA. The arrangement of genes in Mytilus mtDNA is remarkably unlike that found in any other known metazoan mtDNA.
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PMID:A novel mitochondrial genome organization for the blue mussel, Mytilus edulis. 138 86

The nucleotide sequences of the mitochondrial DNA (mtDNA) molecules of two nematodes, Caenorhabditis elegans [13,794 nucleotide pairs (ntp)], and Ascaris suum (14,284 ntp) are presented and compared. Each molecule contains the genes for two ribosomal RNAs (s-rRNA and l-rRNA), 22 transfer RNAs (tRNAs) and 12 proteins, all of which are transcribed in the same direction. The protein genes are the same as 12 of the 13 protein genes found in other metazoan mtDNAs: Cyt b, cytochrome b; COI-III, cytochrome c oxidase subunits I-III; ATPase6, Fo ATPase subunit 6; ND1-6 and 4L, NADH dehydrogenase subunits 1-6 and 4L: a gene for ATPase subunit 8, common to other metazoan mtDNAs, has not been identified in nematode mtDNAs. The C. elegans and A. suum mtDNA molecules both include an apparently noncoding sequence that contains runs of AT dinucleotides, and direct and inverted repeats (the AT region: 466 and 886 ntp, respectively). A second, apparently noncoding sequence in the C. elegans and A. suum mtDNA molecules (109 and 117 ntp, respectively) includes a single, hairpin-forming structure. There are only 38 and 89 other intergenic nucleotides in the C. elegans and A. suum mtDNAs, and no introns. Gene arrangements are identical in the C. elegans and A. suum mtDNA molecules except that the AT regions have different relative locations. However, the arrangement of genes in the two nematode mtDNAs differs extensively from gene arrangements in all other sequenced metazoan mtDNAs. Unusual features regarding nematode mitochondrial tRNA genes and mitochondrial protein gene initiation codons, previously described by us, are reviewed. In the C. elegans and A. suum mt-genetic codes, AGA and AGG specify serine, TGA specifies tryptophan and ATA specifies methionine. From considerations of amino acid and nucleotide sequence similarities it appears likely that the C. elegans and A. suum ancestral lines diverged close to the time of divergence of the cow and human ancestral lines, about 80 million years ago.
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PMID:The mitochondrial genomes of two nematodes, Caenorhabditis elegans and Ascaris suum. 155 72

The cytochrome b-c1 complex from Rhodobacter sphaeroides was resolved into four protein subunits by a phenyl-Sepharose CL-4B column eluted with different detergents. Individual subunits were purified to homogeneity. Antibodies against subunit IV (Mr = 15,000) were raised and purified. These antibodies had a high titer with isolated subunit IV and with the b-c1 complex from R. sphaeroides. They inhibited 95% of the ubiquinol-cytochrome c reductase activity of the cytochrome b-c1 complex, indicating that subunit IV is essential for the catalytic function of this complex. When detergent-solubilized chromatopores were passed through an anti-subunit IV coupled Affi-Gel 10 column, no no ubiquinol-cytochrome c reductase activity was detected in the effluent, and four proteins, corresponding to the four subunits in the isolated complex, were adsorbed to the column. This indicated that subunit IV in an integral part of the cytochrome b-c1 complex. No change in the apparent Kms for Q2H2 and for cytochrome c was observed with anti-subunit IV treated complex. Antibodies against subunit IV had little effect on the stability of the ubisemiquinone radical in this complex, suggesting that they do not bind to the subunit near its ubiquinone-binding site.
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PMID:Essentiality of the molecular weight 15,000 protein (subunit IV) in the cytochrome b-c1 complex of Rhodobacter sphaeroides. 164 84

We studied the possible relationships between the functional status of the beta-cell and activities or mRNA contents of enzymes involved in the catabolism of glucose. Three different in vitro models with attenuated insulin response were used: rat islets cultured at a low glucose concentration, rat islets incubated in vitro with streptozocin, and fetal rat islets. The fetal and streptozocin-administered islets were compared with adult islets cultured in RPMI-1640 containing 11 mM glucose, and the effects of the in vitro glucose concentrations (3.3, 11, and 28 mM) were assessed on adult islets only. Cellular mRNA levels for the mitochondrial DNA-encoded cytochrome b and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by Northern-blot analysis. Enzymatic activities of high-Km (glucokinase) and low-Km (hexokinase) glucose-phosphorylating enzymes and succinate-cytochrome c reductase were also determined. Islets cultured at 3.3 mM glucose displayed a decreased activity of glucokinase compared with islets cultured at 28 mM glucose (23.3 +/- 12%), whereas there was no difference in hexokinase activity or the level of GAPDH mRNA. The activity of succinate-cytochrome c reductase was similar in islets cultured at the different glucose concentrations. The level of cytochrome b mRNA increased at 28 mM glucose compared with islets cultured at 11 mM glucose (140 +/- 14%). Islets incubated with streptozocin and subsequently cultured for 7 days at 11 mM glucose exhibited a decreased level of cytochrome b mRNA (65 +/- 5%) and no differences in the activities of glucokinase, hexokinase, succinate-cytochrome c reductase, or the level of GAPDH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Exhibition of specific alterations in activities and mRNA levels of rat islet glycolytic and mitochondrial enzymes in three different in vitro model systems for attenuated insulin release. 164 83


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