Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A comparison has been made of the effect of 1H,2H,4H(5H)-octafluorocyclohexane, which is highly toxic (LD(50) 17mg./kg. in rats), and of 1H,4H(2H)-nonafluorocyclohexane, which is relatively non-toxic (LD(50)>440mg./kg. in rats), on the respiration of rat liver homogenates and mitochondria in vitro. 1H,2H,4H(5H)-Octafluorocyclohexane strongly inhibited the respiration of both homogenates and mitochondria, but neither compound had any significant effect on glycolysis or on glutamate dehydrogenase or NADH-cytochrome c reductase activity. 1H,2H,4H(5H)-Octafluorocyclohexane, however, caused a very marked inhibition of cytochrome oxidase activity, causing an almost complete lesion in this region of the respiratory chain. 1H,4H(2H)-Nonafluorocyclohexane was without effect in this respect. A marked decrease in turbidity of mitochondrial suspensions at 520nm. was caused by addition of both compounds, the effect being greater with 1H,2H,4H(5H)-octafluorocyclohexane. ATP, Mg(2+) and bovine serum albumin did not reverse these changes. Mitochondrial adenosine triphosphatase activity was increased twofold by the toxic compound, but only slightly by the non-toxic compound. Electron-microscopic examination of mitochondria treated with 1H,2H,4H(5H)-octafluorocyclohexane revealed gross morphological damage, whereas the effect of 1H,4H(2H)-nonafluorocyclohexane appeared to be merely to cause swelling. The results obtained account, to some extent at any rate, for the toxic effects of 1H,2H,4H(5H)-octafluorocyclohexane.
 ...
PMID:Studies in vitro on the effects of 1H,2H,4H(5H)-octafluorocyclohexane and 1H,4H(2H)-nonafluorocyclohexane on enzymes and organelles. 431 59

A study was made of the enzyme content of the isolated cell walls and of a plasma-membrane preparation obtained by centrifugation after enzymic digestion of the cell walls of baker's yeast. The isolated cell walls showed no hexokinase, alkaline phosphatase, esterase or NADH oxidase activity. It was concluded that these enzymes exist only in the interior of the cell. Further, only a negligible activity of deamidase was detectable in the cell walls. Noticeable amounts of saccharase, phosphatases hydrolysing p-nitrophenyl phosphate, ATP, ADP, thiamin pyrophosphate and PP(i), with optimum activity at pH3-4, and an activity of Mg(2+)-dependent adenosine triphosphatase at neutral pH, were found in the isolated cell walls. During enzymic digestion, the other activities appearing in the cell walls were mostly released into the medium, but the bulk of the Mg(2+)-dependent adenosine triphosphatase remained in the plasma-membrane preparation. Accordingly, it may be assumed that the enzymes released into the medium during digestion are located in the cell wall outside the plasma membrane, whereas the Mg(2+)-dependent adenosine triphosphatase is an enzyme of the plasma membrane. This enzyme differs from the phosphatases with pH optima in the range pH3-4 with regard to location, pH optimum, substrate specificity and different requirement of activators.
 ...
PMID:The enzymic composition of the isolated cell wall and plasma membrane of baker's yeast. 431 24

1. During anaerobic glucose de-repression the respiration rate of whole cells of Saccharomyces carlsbergensis remained constant and was insensitive to antimycin A but was inhibited by 30% by KCN. Aeration of cells for 1 h led to increased respiration rate which was inhibited by 80% by antimycin A or KCN. 2. Homogenates were prepared from sphaeroplasts of anaerobically grown, glucose de-repressed cells and the distribution of marker enzymes was investigated after zonal centrifugation on sucrose gradients containing MgCl(2). These homogenates contained no detectable cytochrome c oxidase or catalase activity. The complex density distributions of NADH- and NADPH-cytochrome c oxidoreductases and adenosine triphosphatase(s) [ATPase(s)] were very different from those of anaerobically grown, glucose-repressed cells. 3. The specific activity of total ATPase was lowered and sensitivity to oligomycin decreased from 58 to 7% during de-repression. 4. Cytochrome c oxidase and catalase activities were detectable in homogenates of cells after 10min aeration. Zonal centrifugation indicated complex, broad sedimentable distributions of all enzyme activities assayed; the peaks of activity were at 1.27g/ml. 5. Centrifugation of homogenates of cells adapted for 30min and 3 h indicated a shift of density of the major sedimentable peak from 1.25g/ml (30min) to 1.235g/ml (3 h). After 30min adaptation a minor zone of oligomycin-sensitive ATPase and 15% of the total cytochrome c oxidase activities were detected at rho=1.12g/l; these particles together with those of higher density containing cytochrome c oxidase, ATPase and NADH-cytochrome c oxidoreductase activities were all sedimented at 10(5)g-min. 6. Electron microscopy indicated that the mitochondria-like structures of anaerobically grown, glucose-de-repressed cells were similar to those of repressed cells. After 10min of respiratory adaptation highly organized mitochondria were evident which resembled the condensed forms of mitochondria of aerobically grown, glucose-de-repressed cells. High-density zonal fractions of homogenates of cells after adaptation also contained numerous electron-dense vesicles 0.05-0.2mum in diameter. 7. The possibility that the ;promitochondria' of anaerobically grown cells may not be the direct structural precursors of fully functional mitochondria is discussed.
 ...
PMID:Changes in enzyme activities and distributions during glucose de-repression and respiratory adaptation of anaerobically grown Saccharomyces carlsbergensis. 435 83

1. alpha-p-Chlorophenoxyisobutyric acid, the ethyl ester of which is widely used as an antihypercholesterolaemic drug, is an inhibitor of energy-transfer reactions in isolated rat liver mitochondria. 2. The compound at lower concentrations (<4.0mumol/mg of mitochondrial protein) inhibits state 3 oxidation, stimulates state 4 oxidation, abolishes respiratory control and stimulates the latent adenosine triphosphatase activity of mitochondria. The inhibition imposed on state 3 oxidation is relieved by dinitrophenol. 3. At higher concentrations it inhibits coupled phosphorylation as well as dinitrophenol-stimulated adenosine triphosphatase activity. The inhibition of state 3 oxidation under these conditions is not reversed by uncouplers. 4. The three coupling sites of phosphorylation exhibit differential susceptibility to inactivation by this compound. Coupled phosphorylation at the first site is abolished at a drug concentration of 3.0mumol/mg of protein. The third site is inactivated when the concentration of the drug reaches 5.0mumol/mg of protein. The second site is the most refractory and drug concentrations of the order of 10.0mumol/mg of protein are required effectively to inhibit phosphorylation at this site. 5. The compound also inhibits ATP-dependent reversal of electron transport as well as the adenosine triphosphatase activity in submitochondrial particles. 6. The oxidation of NADH and succinate in these particles is not inhibited. 7. These properties indicate that the compound acts as an ;inhibitory uncoupler' of energy-transfer reactions in isolated mitochondria.
 ...
PMID:Mode of inhibition of mitochondrial energy transduction by chlorophenoxyisobutyrate. 437 92

1. Induction of the formation of lipid peroxide in suspensions of liver microsomal preparations by incubation with ascorbate or NADPH, or by treatment with ionizing radiation, leads to a marked decrease of the activity of glucose 6-phosphatase. 2. The effect of peroxidation can be imitated by treating microsomal suspensions with detergents such as deoxycholate or with phospholipases. 3. The substrate, glucose 6-phosphate, protects the glucose 6-phosphatase activity of microsomal preparations against peroxidation or detergents. 4. The loss of glucose 6-phosphatase activity is not due to the formation of hydroperoxide or formation of malonaldehyde or other breakdown products of peroxidation, all of which are not toxic to the enzyme. 5. All experiments lead to the conclusion that the loss of activity of glucose 6-phosphatase resulting from peroxidation is a consequence of loss of membrane structure essential for the activity of the enzyme. 6. In addition to glucose 6-phosphatase, oxidative demethylation of aminopyrine or p-chloro-N-methylaniline, hydroxylation of aniline, NADPH oxidation and menadione-dependent NADPH oxidation are also strongly inhibited by peroxidation. However, another group of enzymes separated with the microsomal fraction, including NAD(+)/NADP(+) glycohydrolase, adenosine triphosphatase, esterase and NADH-cytochrome c reductase are not inactivated by peroxidation. This group is not readily inactivated by treatment with detergents. 7. Lipid peroxidation, by controlling membrane integrity, may exert a regulating effect on the oxidative metabolism and carbohydrate metabolism of the endoplasmic reticulum in vivo.
 ...
PMID:Effects of lipid peroxidation on membrane-bound enzymes of the endoplasmic reticulum. 439 3

1. The values of the protein, RNA and phospholipid concentrations within the total microsomal fractions obtained from different stages of embryonic chick liver are compared. 2. Only the phospholipid content increases significantly with increasing developmental age. 3. The lack of membranes in the early stages of development and the relative constancy of RNA values during development suggests that some of the protein present at the early developmental stages is of a non-membranous non-ribosomal nature. 4. Glucose 6-phosphatase, adenosine triphosphatase, NADH(2)-cytochrome c reductase and diaphorase all increased in activity as development progressed. 5. Comparisons of submicrosomal fractions with respect to their protein, RNA and phospholipid content showed that in all embryonic stages fraction II (rough-membrane fraction) contained more than 60% of the proteins, RNA and phospholipid of the microsomal fraction. 6. Glucose 6-phosphatase was shown to be present predominantly in fraction II, whereas adenosine triphosphatase was present predominantly in fraction Iab (smooth-membrane fraction). 7. The significance of the differences between the smooth- and rough-microsomal fractions is discussed.
 ...
PMID:Changes in the chemical composition and the enzymic activities of hepatic microsomes of the chick embryo during development. 604 89

Cell lines resistant to ethidium bromide have been developed from cultured mammalian BHK21/C13 cells and these same cells transformed by Rous sarcoma virus (C13/B4). Cells resistant to 2 micrograms ethidium bromide per milliliter have been cloned. One clone of the control and one of the virus-transformed cell lines has been employed for characterization. The resistant cells, in the presence of 2 micrograms ethidium bromide/ml, grow at approximately the same rate as the untreated parental cells. The control cells possess a "normal" karyotype (44 chromosomes), while the corresponding ethidium bromide mutant has a reduced chromosome number of 41 and a number of translocations. The mitochondria displayed morphological alterations compared to the parental lines during the transition phase prior to the isolation of the ethidium bromide-resistant cells. The mitochondria of the ethidium bromide-resistant mutants appear somewhat enlarged with a normal morphology. The effect of ethidium bromide on selected respiratory enzymes in normal and virus-transformed ethidium bromide-resistant baby hamster kidney cells was determined. Ethidium bromide-resistant cells exhibited a depressed level of cytochrome aa3. This depression could not be reversed by growth in ethidium bromide-free media. Ethidium bromide-resistant cells possessed the same cytochrome b, c, and c1 levels per cell as their corresponding parental lines. Purified mitochondria isolated from virus-transformed ethidium bromide-resistant cells exhibited a depression in cytochrome oxidase-specific activity, while the ethidium bromide-resistant control cells did not. All cell lines studied showed a depression in NADH-ferricyanide and NADH-cytochrome c reductase-specific activities relative to their parental BHK21/C13 cells. No increase was observed in virus-transformed ethidium bromide-resistant cells. Ethidium bromide-resistant control cells exhibited a two-fold increase in oligomycin-insensitive adenosine triphosphatase activity relative to their parental cells. All of the cell lines studied possessed equivalent oligomycin-sensitive adenosine triphosphatase-specific activity except for the virus-transformed, dye-resistant mutant, whose activity was increased.
 ...
PMID:Control and virus-transformed baby hamster kidney cells resistant to ethidium bromide. I. Characterization and the respiratory enzymes. 625 Oct 98

Cellular oxygen consumption was monitored during stimulation and inhibition of the Na+- and K+-dependent adenosine triphosphatase in a suspension of intact tubules isolated from the rabbit renal cortex. Respiratory rates were compared to the ADP-stimulated respiratory rate (state 3 rate) obtained in mitochondria released directly from the renal tubules by digitonin shock. At 37 degrees C, in the presence of NADH-linked substrates and fats, isolated renal cells respire at 50 to 60% of the state 3 rate. Inhibition of the (Na+,K+)-ATPase with the cardiac glycoside, ouabain, results in a decline in respiration to 25 to 30% of the state 3 rate. Stimulation of the (Na+,K+)-ATPase produced as a result of nystatin-mediated dissipation of plasma membrane Na+ and K+ gradients results in increased respiration with an oxygen consumption rate characteristic of optimal ATP synthesis (state 3). The relationship between metabolic substrate regimen, mitochondrial respiratory capacity, and cellular energy demand is examined in the context of these findings.
 ...
PMID:Mitochondrial respiratory capacity and Na+- and K+-dependent adenosine triphosphatase-mediated ion transport in the intact renal cell. 627 Jan 7

Altered erythrocyte sodium potassium (Na,K)-stimulated adenosine triphosphatase (ATPase) activity has been cited as having pathophysiologic significance in morbidly obese man. Previous studies have failed to consider obese patients after weight loss and, therefore, did not clarify the role of ATPase deficiency as a cause or effect of the obese state. To define more completely the possible alteration of cellular thermogenesis in obesity, a study was made of three groups of people: (1) normal weight controls; (2) morbidly obese; and (3) formerly morbidly obese patients who had lost over 100 pounds after gastric bypass surgery. Erythrocyte ATPase activity was determined by use of an assay that coupled ATPase activity with NADH oxidation in the presence of excess pyruvate kinase, lactic dehydrogenase, and phosphoenolpyruvate. This coupled assay produced a continuous slope so that activity could be calculated from the initial, maximal, linear portion of the decay trace. Results did not demonstrate any statistically significant differences in Na,K-ATPase activity between groups by analysis of variance. A nonsignificant correlation of 0.086 was seen between obesity index and Na,K-ATPase activity. It is concluded that (1) erythrocyte Na,K-ATPase activity is similar in both normal and obese individuals, (2) erythrocyte Na,K-ATPase does not change with weight loss, and (3) therefore, disordered erythrocyte thermogenesis does not have a role in the development or maintenance of obesity.
 ...
PMID:Erythrocyte sodium-potassium-stimulated adenosine triphosphatase activity is not related to obesity. 630 95

In porcine interareolar placental epithelia, the following enzymes were demonstrated by histochemical methods after 30, 58, 80, 100, and 110 d of pregnancy, respectively: beta-N-acetylhexosaminidase, beta-galactosidase, beta-glucuronidase, alpha-mannosidase, acid phosphatase, alkaline phosphatase, nonspecific esterases, cytochrome oxidase, 5-nucleotidase, leucine aminopeptidase, adenosine triphosphatase, diaphorases (NADH, NADPH), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase (NAD, NADP), beta-hydroxybutyrate dehydrogenase, glycero-3-phosphate dehydrogenase, NAD-glycero-3-phosphate dehydrogenase, glutamate dehydrogenase (NAD, NADP), lactate dehydrogenase. The results show that most of the enzyme activities remained almost unchanged during the period of investigation. Only G-6-PDH and 6-PGDH activities increased within the uterine epithelium and nonspecific esterase activity within uterine as well as chorionic epithelia during the 2nd half of pregnancy. Within chorionic and uterine epithelia, hydrolases but not dehydrogenases demonstrated a higher activity at the bases of chorionic villi as compared to the apices and flanks of the latter. The action and influence of the demonstrated enzymes on metabolism, energy transfer, secretory, and resorptive activities of chorionic and uterine epithelia are discussed.
 ...
PMID:[Enzyme histochemical studies of the swine placenta. Histoptics of enzymes in interareolar placental epithelia]. 643 35


<< Previous 1 2 3 4 5 6 7 Next >>