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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Freezing-thawing of rat liver mitochondria evokes a release of Ca2+ into the incubation medium containing oxidation substrates: succinate and phosphate. The release is accompanied by a decrease in the membrane potential value. ATPase and NADH-dehydrogenase inhibitors when introduced into the medium simultaneously with mitochondria prevent the both processes, but only till Ca2+ release. ADP added during Ca2+ release, initiates its uptake. When succinate is replaced by NAD-dependent substrates (malate in combination with glutamate) and in the presence of the antioxidant (ionol) Ca2+ is not released from mitochondria. It is supposed that Ca2+ release from mitochondria due to freezing-thawing is evoked by activation of lipid peroxidation and is controlled by the degree of pyridine nucleotide reduction.
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PMID:[Ca2+ release from rat liver mitochondria subjected to deep freezing]. 649 7

Metabolic changes may precede changes in lens protein structure and cataract opacification. Since many of the effects associated with cataract are oxidative in nature, changes in the redox state may be caused by alterations in the level of various metabolic intermediates such as ATP and NAD(P)H. Abnormal levels of H2O2 have been found in the aqueous fluid of cataract patients. Lenses have been treated with 1 mM-H2O2 in organ culture as a cataract model. H2O2 in this system uncouples Na+, K+-ATPase. This metabolic stress has been further evaluated non-invasively by 31P NMR to show that H2O2 can reduce ATP levels without any immediate effects on visual transparency. However, further treatment by this oxidant leads to definitive visual changes in lens clarity. These changes may be due to further changes in structural lens proteins caused by denaturation and aggregation induced by H2O2. The effects of H2O2 on isolated lens proteins is being examined in molecular detail by NMR to ascertain how the lens proteins become denatured in solution. The relevance of the H2O2 model to cataract formation can only be evaluated by using several non-invasive techniques beyond NMR, and then critically comparing the model systems with human cataract tissue samples.
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PMID:Non-invasive techniques in the study of cataract development at the metabolic and protein molecular level. 656 77

The effect of short-term treatment of rats with the synthetic glucocorticoid, dexamethasone, on mitochondrial oxidative phosphorylation has been examined. Treatment of rats for 3 h increased the oxidative capacity of the subsequently isolated mitochondria such that they displayed increased uncoupled and State 3 rates of respiration with NAD-linked substrates, succinate or durohydroquinone. The oxidation of ascorbate plus N,N,N',N'-tetramethyl-p-phenylenediamine was unaffected. No change was apparent in the activity of a variety of dehydrogenase enzymes nor was there any increase in the mitochondrial content of cytochromes a, b, c1 or c. The uncoupler-dependent ATPase activity of the mitochondria was slightly enhanced following hormone treatment, but not the basal or the total ATPase activity measured in the presence of Triton X-100 plus Mg2+. The mitochondria prepared from dexamethasone-treated rats also displayed increased intramitochondrial concentrations of Mg2+, K+ and exchangeable adenine nucleotides but not Ca2+. It is suggested that the effect of glucocorticoids on mitochondrial respiration may be both the result of a direct activation of the respiratory chain within Complex III and an elevated intramitochondrial adenine nucleotide concentration. The evidence for the de novo synthesis of mitochondrial proteins which mediate the response remains inconclusive.
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PMID:The stimulation of hepatic oxidative phosphorylation following dexamethasone treatment of rats. 662 40

The effect of the association of gossypol and Lonidamine on the electron transport in Ehrlich ascites tumor mitochondria has been investigated by addition of drugs to isolated mitochondria. The results may be summarized as follows. (1) Low concentrations of gossypol increase the rate of oxygen consumption at the level of three energy-conserving sites of the respiratory chain. Higher concentrations result in an inhibition of oxygen consumption at (or near) both energy-conserving sites 1 and 2, while energy-conserving site 3 is unaffected. (2) Gossypol, at concentrations at which it exerts its uncoupling effect, stimulates ATPase activity. Higher concentrations inhibit the enzyme activity. (3) The addition of gossypol to mitochondria respiring on pyruvate plus malate or succinate induces a more oxidized state of NAD+ and cytochrome b, respectively. (4) Gossypol enhances the effect of Lonidamine on oxygen consumption. Lonidamine does not affect state 4 respiration, but in the presence of gossypol, it determines a marked decrease in the rate of oxygen consumption. The inhibition of oxidation of NAD-linked substrates is greater than that of FAD-linked substrates. (5) It may be concluded that gossypol is very effective in potentiating the effect of Lonidamine. Moreover, it may be suggested that the antitumor activity of Lonidamine is enhanced if it is used in combination with other drugs and/or treatments, such as hyperthermia, which modify the energy status of mitochondria.
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PMID:The effect of gossypol and Lonidamine on electron transport in Ehrlich ascites tumor mitochondria. 670 94

The effects of glucose on cellular respiration were examined in suspensions of rabbit cortical tubules. When glucose was removed from the bathing fluid, oxygen consumption (QO2) decreased from 18.6 +/- 0.8 to 15.7 +/- 0.5 nmol O2/mg protein X min (P less than 0.01). The transported but nonmetabolized analogue of glucose, alpha-methyl-D-glucoside (alpha MG), was found to support QO2 to the same extent as glucose. These observations were also evident in the presence of butyrate, a readily oxidized substrate of the renal cortex. Additional studies with nystatin and ouabain indicated that glucose-related changes in QO2 were the result of changes in Na, K-ATPase associated respiration. The effect of glucose was localized to the luminal membrane since phlorizin (10(-5) M), a specific inhibitor of luminal glucose-sodium cotransport, also significantly reduced QO2 by 10 +/- 1%. Phlorizin inhibition of QO2 was also evident in the presence of alpha MG but was abolished when glucose was removed from the bathing medium. Finally, measurement of NADH fluorescence showed that addition of glucose (5 mM) to a tubule suspension causes an oxidation of NAD. These data are all consistent with glucose acting to increase respiration by stimulating sodium entry at the luminal membrane (via glucose-sodium cotransport) followed by increased sodium pump activity and its associated increase in mitochondrial respiration.
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PMID:Glucose-dependent respiration in suspensions of rabbit cortical tubules. 672 93

Parallel stereo- and cytospectrophotometric examinations of human myocardial capillaries, 20-60 min after biological death were carried out. The activity of alkaline phosphatase, adenosine triphosphatase, lactate dehydrogenase and NAD-diaphorase in the capillary wall in relation to the sex and age in cardiovascular pathology, renal diseases and leukemias were studied. The permeability and level of energy supply of transendothelial transport were found to depend on the kind of the main pathological process and type of death. According to the parameters under study, the functional state of the capillary network of the myocardium in atherosclerosis with or without its combination with hypertension and also in secondary renal hypertension is described.
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PMID:[Stereological characteristics and enzymatic activity of myocardial capillaries in different variants of pathology and death (data from immediate autopsies)]. 686 Jan 68

1. The redox state of mitochondrial NAD was monitored fluorometrically as a function of active ion transport work in the isolated doubly perfused bullfrog kidney. 2. Initial experiments to measure the O2 consumption (QO2) of small pieces from the bullfrog kidney gave a basal QO2 - 3.0 (+/- 0.43) nmoles O2/mg dry wt. min. Addition of 50 microM-ouabain inhibited QO2 by 72.7%. Subsequent addition of the mitochondrial uncoupler 1799 stimulated QO2 by 226%, while cyanide totally inhibited respiration. 3. Ion transport functional parameters and NADH fluorescence were simultaneously monitored during systematic reductions in perfusate PO2 to test the sufficiency of O2 delivery to the isolated perfused frog kidney. No significant changes in transport functions or fluorescence were observed until the PO2 dropped to 184 mm Hg or below. O2 tensions of 184 mm Hg or below caused decreases in G.F.R. and transport functions which were accompanied by an increase in NADH fluorescence. The lack of changes in kidney function in the PO2 range 550-340 mmHg suggested that the tissue is adequately oxygenated at the normal perfusate PO2 of 550 mmHg. 4. The relationship between active transport rate and NAD redox levels was studied by increasing transport work (via increased G.F.R. or ADH) or by decreasing transport work (via decreased G.F.R. or ouabain) while simultaneously monitoring the NAD redox state of the intact tissue fluorometrically. In all cases, an increase in work caused a net oxidation of NAD while a decrease in work caused a reduction of NAD. 5. It is concluded that the NADH fluorescence responses are indicative of mitochondrial active to passive transitions in response to changes in active transport work. The aerobic production of ATP and the normally functioning Na-K-ATPase appear to be essential to maintain active transport and to elicit the appropriate state transitions. Thus, ATP (and, possibly, ADP and Pi) may be part of the coupling mechanism linking active ion transport and aerobic metabolic rate in the kidney.
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PMID:Coupling of aerobic metabolism to active ion transport in the kidney. 696 4

The author reviews his own and reported data on the action of toxic substances of varying chemical classes on the main stages of the process of oxidative phosphorylation. It has been shown that toxic substances can destroy oxidative phosphorylation by the following ways: by reducing the resistance of mitochondrial membranes (disconnectors of the protonophoric and ionophoric types); by inhibiting dehydrogenase activity; by disturbing electron transfer via the respiratory chain; by disordering transmembrane transport of cations or anions; by inhibiting ATPase activity. The characteristic classes of toxic substances and the most specific inhibitors are indicated for each of the points enumerated. It is pointed out that the most incident reasons for impairment of oxidative phosphorylation are inhibition of NAD X H-dehydrogenase and protonophoric dissociation of respiration and phosphorylation.
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PMID:[Classification of xenobiotics according to their effect on mitochondrial enzymatic systems]. 717 25

It has recently been found that ortho- or metavanadate can effectively block (Na+ + K+)ATPase and that it loses its blocking potency when reduced to the vanadyl (VO2+) ion. The question arose whether vanadate could be involved (reduced) in an NAD-linked enzymatic redox system of the cell. Here we have studied the effect of vanadate on malate dehydrogenase (MDH, EC1.1.1.37) catalysed oxidation of NADH during the formation of malate from oxalacetate in vitro. The MDH reaction was accelerated by vanadate, but we found thatr vanadate does not require the presence of any specific enzyme or substrate to mediate NADH oxidation.
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PMID:A specific enzyme is not necessary for vanadate-induced oxidation of NADH. 740 32

Plasma membranes purified from onion roots contain two distinct NAD(P)H-dehydrogenases of 27 and 31 kDa that differ in their physicochemical properties, substrate specificities and inhibitors sensitivities. The 27-kDa enzyme used both NADH and NADPH as electron donors. The 31-kDa enzyme was fully specific for NADH and accounted for the bulk of NADH-ferricyanide oxidoreductase. We have used NADPH- and NADH-ferricyanide oxidoreductase activities as markers for investigating the orientation of the 27- and 31-kDa enzymes at the plasma membrane, respectively. These activities were assayed in right-side-out vesicles isolated by two-phase partition, inside-out vesicles obtained by treatment with the detergent Brij 58 and membranes permeabilized with Triton X-100. Upon addition of Brij 58 to right-side-out plasma membrane vesicles, both NADPH- and NADH-ferricyanide oxidoreductases were activated to the same degree as the plasma membrane H(+)-ATPase. Redox activities were similar when measured in the presence of either Brij 58 or Triton X-100. Our results demonstrate that both enzymes expose their catalytic sites toward the cytoplasmic side of the plasma membrane.
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PMID:Topography of the 27- and 31-kDa electron transport proteins in the onion root plasma membrane. 748 79


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