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:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of acute hypoxia on adenine nucleotides, glutamate, aspartate, alanine and respiration of heart mitochondria was studied in rats. The losses of intramitochondrial adenine nucleotides (ATP+ADP+AMP) during hypoxia were related to depression of state 3 respiration supported by glutamate and malate, as well as decrease in uncoupled respiration. Hypoxia had less prominent effect on succinate-dependent state 3 respiration. Non-phosphorylating (state 4) respiratory rates and ADP/O ratios were slightly affected by oxygen deprivation. Glutamate fall in tissue and mitochondria of hypoxic hearts was concomitant with significant increase in tissue alanine and mitochondrial aspartate. The losses of intramitochondrial ATP and respiratory activity with NAD-dependent substrates during hypoxia were related to a decrease in mitochondrial glutamate. The results suggest that hypoxia-induced impairment of complex I of respiratory chain and a loss of glutamate from the matrix may limit energy-producing capacity of heart mitochondria.
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PMID:Adenine nucleotides, glutamate and respiratory function of heart mitochondria during acute hypoxia. 375 8

Low concentrations of cadmium (3.3-40 microM) inhibited State 3 NADH-linked respiration in rat hepatic mitochondria, but failed to release oligomycin (1 microgram) inhibited State 3 respiration, or to significantly change the State 4 rate. In the presence of succinate, 40 microM cadmium inhibited State 3 respiration by 89%, while concentrations between 3.3 and 13.3 microM stimulated State 4 respiration. Higher concentrations caused marked inhibition. In the presence of succinate, cadmium released oligomycin inhibited State 3 respiration. Cadmium (0.001-1.0 mM) did not stimulate mitochondrial ATPase activity or inhibit ferricyanide reduction, but stimulated NAD+ linked mitochondrial dehydrogenase activities and NADH oxidation. These results indicate that cadmium interacts with either the NADH dehydrogenase complex or other NADH-dependent enzymes and not solely by an uncoupling action.
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PMID:The effects of cadmium on succinate and NADH-linked substrate oxidations in rat hepatic mitochondria. 377 8

Though previously described as very low or absent in yeast, we find significant pyridine nucleotide transhydrogenation (NADPH + acetyl pyridine-NAD+----NADP+ + acetyl pyridine-NADH) activity in yeast extracts when assayed at pH 8-9, and describe here the subcellular distribution and separation of the various molecular forms contributing to the total activity in two yeast species. Gentle subcellular fractionation reveals transhydrogenase activity only in the cytosolic fraction of both Saccharomyces cerevisiae and Candida utilis while intact mitochondria and microsomes are without activity. On sucrose gradient centrifugation, this soluble cytosolic activity proves to be primarily in a high-molecular-weight (greater than 10(6)) band which has salmon-colored fluorescence on uv illumination. Sonication of the particulate subcellular fractions solubilizes substantial transhydrogenase activity from mitochondria of C. utilis (but not from S. cerevisiae) which on sucrose gradients consists of both high (greater than 10(6))- and low-molecular-weight active fractions, each with yellow-green fluorescence. Ammonium sulfate fractionation and sucrose gradient centrifugation of protein solubilized from whole yeast of both species by vigorous homogenization with glass beads confirms the presence and fluorescence of these various molecular weight forms. The relationship of these activities to other enzymatic activities (especially the mitochondrial external NADH dehydrogenase) is discussed.
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PMID:Pyridine nucleotide transhydrogenations in yeast. 390 68

The NADH and NADPH ferricyanide reductase activities present in mitochondrial NADH-CoQ reductase preparations have been studied utilizing two photoaffinity pyridine nucleotide analogues: arylazido-beta-alanyl NAD+ (A3'-O-[3-[N-(4-azido-2-nitrophenyl)amino]propionyl]NAD+) and arylazido-beta-alanyl NADP+ (N3'-O-[3-[N-(4-azido-3-nitrophenyl)amino]propionyl]NADP+). For the NADH-K3Fe(CN)6 reductase activity, arylazido-beta-alanyl NAD+ was found to be, in the dark, a competitive inhibitor with respect to both NADH and K3Fe(CN)6 with Ki,app values of 9.7 and 15.5 microM, respectively. In comparison the NADP+ analogue exhibited weak noncompetitive inhibitor activity for this reaction against both substrates. Upon photoirradiation arylazido-beta-alanyl NAD+ inhibited NADH-K3Fe(CN)6 reductase up to 70% in the presence of a 25-fold molar excess of analogue over the enzyme concentration. This photodependent inhibition could be prevented by the presence, during irradiation, of the natural substrate NADH. In contrast complex kinetic results were obtained with studies of the effects of the pyridine nucleotide analogues of NADPH-K3Fe(CN)6 reductase activity in the dark. Photoirradiation of either analogue in the presence of the enzyme complex resulted in an activation of NADPH-dependent activity. The possibility that the NADPH-K3Fe(CN)6 reductase activity of complex I represents a summation of the combined ferricyanide reductase activity of the NADPH-NAD+ transhydrogenase and NADH oxidoreductase is suggested.
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PMID:Studies of the ferricyanide reductase activities of the mitochondrial reduced nicotinamide adenine dinucleotide-ubiquinone reductase (complex I) utilizing arylazido-beta-alanyl NAD+ and arylazido-beta-alanyl NADP+. 392 31

We examined the activity of heme synthesis when ferrochelatase purified from rat liver mitochondria was incubated with ferric chloride and mesoporphyrin IX as substrates in the absence of reducing reagents. In the presence of the NADH dehydrogenase-rich fraction and NAD(P)H, mesoheme was synthesized; the addition of FMN or FAD markedly enhanced the activity. These results indicate that the NAD(P) H-oxidizing system reduces ferric ion to ferrous ion. This ferrous ion is then utilized for heme synthesis by ferrochelatase. The effect of lead on NAD(P)H-dependent heme synthesis was also examined. Lead reduced NAD(P)H-dependent heme synthesis by 50% at 10(-5) M, but had no effect when ferrous ion was used as substrate. Zn-Porphyrin synthesis was not changed in the presence of Pb2+ at 10(-5) M. Thus, heme synthesis from ferric ion was more susceptible to Pb2+ than heme synthesis from ferrous ion.
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PMID:Reconstitution of heme-synthesizing activity from ferric ion and porphyrins, and the effect of lead on the activity. 393 55

A membrane-associated NADH dehydrogenase from beef neutrophils was purified to homogeneity, using detergent (cholate plus Triton X-100) extraction and chromatography on DEAE-Sepharose CL-6B, agarose-hexane-NAD, and hydroxylapatite. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed an apparent subunit molecular weight of 17,500, but the enzyme was highly aggregated (Mr greater than 450,000) in nondenaturing gels containing 0.1% Triton X-100. The protein band in nondenaturing gels was also stained for activity using NADH and nitro blue tetrazolium. The enzyme showed greatest electron acceptor activity with ferricyanide (100%), followed by cytochrome c (3.5%), dichloroindophenol (2.7%), and cytochrome b5 (0.34%). No activity was seen with oxygen. The Km values for NADH and ferricyanide were 18 and 9.5 microM, respectively, and NAD+ was a weak competitive inhibitor (Ki = 118 microM). No activity was seen with NADPH. No effects were seen with mitochondrial respiratory inhibitors such as azide, cyanide, or rotenone, but p-chloromercuribenzoate was strongly inhibitory and N-ethylmaleimide was weakly inhibitory. No free flavin was detectable in enzyme preparations. Based upon kinetic, physical, and inhibition properties, this NADH dehydrogenase differs from those previously described in microsomes and erythrocyte plasma membrane.
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PMID:NADH dehydrogenase from bovine neutrophil membranes. Purification and properties. 394 Oct 77

The cationic fluorescent dyes, berberines, have been observed to inhibit NAD-linked respiration in rat liver mitochondria. Low concentrations inhibit electron transport in the NAD-ubiquinone span after penetration into mitochondria. More hydrophobic alkyl derivatives proved to be stronger inhibitors showing more rapid onset of inhibition. The inhibition was totally dependent on the energization of the membrane; however, the addition of a hydrophobic anion stimulated the inhibition effects in uncoupled mitochondria. Substantially higher concentrations of berberines are needed for the inhibition of the oxidation of succinate. The excess of dye interacting with surface dipoles in the energized state can inhibit the energy transduction through the complex bc1. On the basis of the difference in the rate of fluorescence response when berberines are added to coupled mitochondria and the corresponding inhibition effects, the presence minimally of two binding sites was suggested. The dye bound on the outer surface is highly fluorescent and inhibits the energy transduction if added in excess. The remaining dye interacting with NADH dehydrogenase does not fluoresce. The accumulation of alkylberberine in mitochondria results in additional effects in the region of cytochrome b the nature of which is not fully understood.
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PMID:Interaction of fluorescent berberine alkyl derivatives with respiratory chain of rat liver mitochondria. 398 24

The purified mitochondrial NADH dehydrogenase enzyme has been shown to catalyze a rapid [4B-3H] NADH-H2O exchange reaction. When the enzyme is subjected to a single freeze-thaw cycle there is a complete loss of NADH dehydrogenation without a measurable decrease in the [4B-3H] NADH-H2O exchange. Complete loss of the [4B-3H] NADH-H2O exchange follows brief exposure to ultraviolet photoirradiation. The differential sensitivity of the water exchange reaction and the dehydrogenase activity suggests a direct involvement of the enzymes flavin cofactor in the catalysis of the [4B-3H] NADH-H2O exchange. Arylazido-beta-alanyl NAD+ (A3'-0-[3-[N-4-azido-2-nitrophenyl)amino] propionyl]NAD+) is shown to be a potent photodependent inhibitor of the [4B-3H] NADH-H2O exchange activity following photoirradiation with visible light. This is consistent with the observed photodependent inhibition of the dehydrogenase activity by this photoprobe (Chen, S. and Guillory, R.J. (1981) J. Biol. Chem. 256, 8318-8323).
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PMID:The [4B-3H] NADH-H2O exchange reaction of the mitochondrial NADH dehydrogenase. 401 47

The fluorescence signal of flavoproteins of rat liver mitochondria was investigated to determine the respective contributions of the various flavoenzymes. About 50% of the overall signal were found to be NAD-linked and caused by alpha-lipoamide dehydrogenase flavin (Em7.4 = -283 mV). Roughly 25% were due to a flavoprotein reducible in a non-NAD-linked reaction. This fluorescent flavoenzyme (Em7.4 = -52 mV) has been tentatively identified as a flavoprotein of the fatty-acid-oxidizing system, most probably the electron transfer flavoprotein. The remaining 25% of the signal are accounted for by flavoenzymes which are reducible by dithionite only. These flavoenzymes were not involved in the flavoprotein fluorescence alterations accompanying changes in electron flow through the respiratory chain. Contributions of other mitochondrial flavoproteins such as succinate dehydrogenase, NADH dehydrogenase, alpha-glycerophosphate dehydrogenase, proline dehydrogenase, and choline oxidase, to the overall flavin fluorescence signal of isolated rat liver mitochondria can be neglected.
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PMID:Contribution of different enzymes to flavoprotein fluorescence of isolated rat liver mitochondria. 402 66

Submitochondrial particles prepared from liver and skeletal muscle of control and iron-deficient rats were examined for cytochrome content and for both energy-independent and energy-conserving functions. Liver submitochondrial particles appear quite resistant to iron deficiency with cytochrome content and electron-transferring or energy-conserving functions maintained at a level of 85% or better of normal. Iron-deficient skeletal muscle submitochondrial particles, in contrast, have decreased cytochrome content and only 15-20% of the normal capacity for oxidation through either complex I (NADH dehydrogenase) or complex II (succinate dehydrogenase). Energy-linked reactions which involve substrate oxidation/reduction (succinate----NAD+ reversed electron flow and succinate-driven energy-dependent transhydrogenation) are likewise markedly decreased, while ATP-driven energy-dependent transhydrogenation and mitochondrial ATPase are normal. Our data support the concept that iron deficiency leads to decreased electron-carrying capacity of iron-containing mitochondrial enzymes, with skeletal muscle being much more susceptible than liver, but that the mitochondria are otherwise normal with regard to energy conservation.
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PMID:Effect of iron deficiency on energy conservation in rat liver and skeletal muscle submitochondrial particles. 405 63


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