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)

It was reported previously that dietary ascorbate (ASC) delays the development of galactose-induced cataract in guinea pigs compared to the rate which is observed in ASC-deficient animals. Experiments were conducted to explore the possible mechanism of this phenomenon. Guinea pigs were fed for a period of up to 4 weeks either a normal diet (1 g ASC/kg diet) or a scorbutic diet (< 0.04 g ASC/kg diet) combined with 10% galactose in the drinking water. After 2 weeks, levels of ASC in animals on the scorbutic diet decreased by 95% in the aqueous humor and by 78% in the lens. Slit lamp examination showed that galactose-induced vacuoles in the lens equator formed at a significantly faster rate in the scorbutic animals. However, examination of biochemical parameters in whole lenses of the two groups of animals after 2 weeks showed no significant differences with regard to accumulation of galactose and galactitol, decreases in the levels of myoinositol, taurine and GSH or changes in cation concentrations. In order to examine possible regional changes in the lenses, various parameters were studied in the lens capsule-epithelium. On day 4, the capsule epithelia of scorbutic animals on a galactose diet had a content of galactitol two-and-a-half times higher than that of normal galactose-fed animals. Scorbutic conditions also intensified the loss of Na(+)-K+ ATPase activity in the lens capsule-epithelium caused by galactose feeding. Oxidized glutathione was not detectable in the lens capsule epithelia of any of the animals studied. Hexose monophosphate shunt activity was elevated in lenses of normal galactose-fed animals during the first hour of culture after death whereas lenses of scorbutic galactose-fed animals were not. Consistent with the in vivo findings, galactitol accumulation in dog lens epithelial cells exposed to 30 mM galactose was significantly inhibited by the presence of either ASC or dehydroascorbate (DHA) in the medium. Hexose monophosphate shunt activity in the cells was stimulated to two-and-a-half times its initial level by either 1 mM DHA or 30 mM galactose and slightly more than three-fold by a combination of the two challenges. The results suggest that decreased polyol accumulation in the lens epithelium of the normal galactose-fed guinea pig, which has a high level of ASC in the aqueous humor, accounts for the delay in onset of cataract compared to that for the ASC-deficient animal.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:A physiological level of ascorbate inhibits galactose cataract in guinea pigs by decreasing polyol accumulation in the lens epithelium: a dehydroascorbate-linked mechanism. 815 13

Incubation of human red blood cells (RBCs) with t-butyl hydroperoxide (tBHP) resulted in inhibition of the Ca-pump ATPase. This was demonstrated using an assay of the Ca-pump ATPase activity in intact RBCs. In this assay, activity of the Ca-pump ATPase is expressed as the rate constant of the initial loss of ATP in RBCs exposed to Ca and A23187. Pseudo-first-order rate constants (Ca-pump ATPase rate constants) were lower in the presence of tBHP versus controls. Incubation of RBCs with tBHP resulted in both a time- and concentration-dependent inhibition of the Ca-pump ATPase (IC50 approximately 1 mM). Incubation of RBCs with tBHP also resulted in decreased oxyhemoglobin, increased methemoglobin and increased thiobarbituric acid reactive substances (TBARS). GSH levels were significantly lower in the presence of tBHP. GSH fell from a control value of 2.2 mmol/l RBC to 0.46 mmol/l RBC after incubation with 0.25 mM tBHP for 15 min. Both butylated hydroxytoluene and stobadine prevented the formation of TBARS and were partially effective in protecting the Ca-pump ATPase from tBHP-induced inhibition. Dithiothreitol was completely effective in preventing the tBHP-induced formation of TBARS as well as inhibition of the Ca-pump ATPase. However, when added after exposure to tBHP, dithiothreitol was unable to restore Ca-pump ATPase activity completely. An activity of dithiothreitol independent of enzymic thiol group reduction was apparent. In the presence of mercaptosuccinate, a potent inhibitor of glutathione peroxidase, the ability of dithiothreitol to protect the Ca-pump ATPase from tBHP-induced inhibition was abolished. Therefore, protection by dithiothreitol may be afforded by its ability to replenish GSH from oxidized glutathione, thus allowing glutathione peroxidase to metabolize tBHP. These results may be interpreted to suggest that inhibition of the Ca-pump ATPase in intact RBCs occurs as a result of tBHP-induced oxidant stress and subsequent lipid peroxidation which can be prevented by certain antioxidants including butylated hydroxytoluene, stobadine, and thiol-containing compounds such as dithiothreitol. These findings provide further insight into the mode of action of hydroperoxides and certain reactive oxygen species that have been implicated in oxidative stress associated with various pathological conditions. The importance of the GSH/glutathione peroxidase system in metabolizing organic hydroperoxides is also demonstrated.
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PMID:Inhibition of the Ca pump of intact red blood cells by t-butyl hydroperoxide: importance of glutathione peroxidase. 824 Dec 52

Extracorporeal dialysis in uremic subjects produces erythrocyte alterations on energetic and redox metabolism. On this basis, we have tried to verify a fundamental parameter for the integrity of the red blood cell namely the glutathione content both in the oxidized and reduced form. Comparisons were made between two groups of subjects (similar in age, sex and number). One group consisted of uremic subjects undergoing dialysis and the other in healthy controls. As well as a slight increase in reduced glutathione (GSH), an accumulation of oxidized glutathione (GSSG) was found which, in postdialysis patients, reached values up to 3 times higher than in controls. This means a lowering in the ratio GSH/GSSG. There was also a decrease in total Mg(++)-ATPase activity, significantly found in erythrocyte ghosts of postdialysis patients. The hypothesis of a reduced efflux of GSSG as well as an increase in its formation speed (activation of glutathione peroxidase) is taken into consideration.
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PMID:[Extracorporeal hemodialysis: various++ metabolic and erythrocyte-membrane features of uremic subjects]. 832 84

The present study was designed to examine the reaction pathway of colloidal bismuth subcitrate (CBS) with thiols. Studies were performed using the monothiol glutathione (GSH), the dithiol dithiothreitol (DTT) and the thiol enzymes papain and H+/K(+)-ATPase. UV-vis spectra showed that CBS forms complexes with GSH and DTT. The GSH/CBS complex but not the DTT/CBS complex was cleared by 5,5'-dithiobis-(2-nitrobenzoic acid). CBS inhibited H+/K(+)-ATPase (IC50: 23 +/- 6.5 mumol/l) but failed to inhibit papain activity. The inhibitory action of CBS on H+/K(+)-ATPase-mediated proton transport was prevented by the dithiol dithioerythritol but not by GSH. These results indicate that CBS forms stable complexes with dithiols and instable complexes with monothiols. We suggest that some of the effects of CBS (i.e., stimulation of prostaglandin production, antibacterial action against Helicobacter pylori) are mediated via the blockade of SH-groups.
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PMID:Studies on the mechanism of action of colloidal bismuth subcitrate. I. Interaction with sulfhydryls. 839 60

We evaluated the specific effects of acrolein on sulfhydryl status and plasma membrane-dependent functions of cultured pulmonary artery endothelial cells. Acrolein exposure caused a dose-dependent increase in lactate dehydrogenase (LDH) release and decreases in reduced glutathione (GSH) and protein sulfhydryl (P-SH) content, whereas oxidized glutathione (GSSG) content was not altered. Exposure to 4.5 microM, but not 1.5 or 3.0 microM, of acrolein caused significant (p < 0.05) LDH release. With increasing concentrations (25 microM) of acrolein, LDH release was increased to 66% (p < 0.001). Acrolein (3.0-25 microM) resulted in 36 to 100% reductions in GSH content, whereas reductions in P-SH content at these concentrations of acrolein ranged from 11 to 37%. Uptake of amino acids (cystine, glycine, and glutamic acid) and incorporation of valine into the protein fraction were significantly reduced in a dose-dependent fashion in acrolein (1.5-4.5 microM)-exposed cells. Reductions in cystine, glycine, and glutamic acid uptakes were maximal in cells exposed to 3 and 4.5 microM acrolein (p < 0.001). Similarly, maximum reductions (p < 0.001) in both uptake and incorporation of valine into the protein fraction were observed at 3.0 and 4.5 microM acrolein. Acrolein (1.5 microM) also resulted in significant loss of plasma membrane-specific Na+/K(+)-ATPase as well as plasma membrane P-SH content (p < 0.05 for both). When cells were treated with ouabain, reductions in amino acid uptake were observed, and this appeared to mimic the effect of acrolein exposure. When isolated plasma membranes were exposed to a known SH-alkylating agent, N-ethylmaleimide, losses of Na+/K(+)-ATPase and P-SH content were observed and were similar to the effects following exposure to acrolein. These results demonstrate that acrolein exposure results in alterations of plasma membrane-dependent transport in pulmonary artery endothelial cells, leading to reduced availability of precursor amino acids used in GSH and protein synthesis. This plasma membrane injury is accompanied by reductions in the GSH and P-SH contents of these cells. Loss of the plasma membrane P-SH appears to be associated with specific inactivation of Na+/K(+)-ATPase.
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PMID:Acrolein-induced injury to cultured pulmonary artery endothelial cells. 839 54

Dinitrophenyl S-glutathione (Dnp-SG) ATPase which catalyses the hydrolysis of ATP in the presence of GSH-conjugates has been implicated previously in the transport of these conjugates. In the present studies we demonstrate that Dnp-SG ATPase is present in bovine lens epithelium and cortex. The specific activity per mg membrane protein was found to be 75-fold higher in the epithelium as compared to the cortex. No enzyme was detected in the nuclear region of the lens. Dnp-SG ATPase was purified from bovine lens epithelium and cortex using Dnp-SG-Sepharose 6MB affinity chromatography. The partially purified Dnp-SG ATPase had two distinct Km values, 120 microM and 1.0 mM. The antibodies raised against human erythrocyte Dnp-SG ATPase cross-reacted with the bovine lens epithelium Dnp-SG ATPase which was identified by Western blot as a band corresponding to an approximate M(r) value of 80,000 Da.
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PMID:Low and high Km forms of dinitrophenylglutathione-stimulated ATPase in bovine lens. 840 91

Liver homogenate and subcellular fractional levels of lipid peroxides, homogenate glutathione (GSH) and calcium contents and hepatic plasma membrane Ca(2+)-ATPase activity were determined in rats, 12, 18, 24 and 48 hours after treatment with a single dose of 1 g/kg galactosamine. Lipid peroxides and calcium levels in liver homogenate and subcellular fractions were found to increase, but hepatic GSH content and Ca(2+)-ATPase activity were observed to decrease reversibly.
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PMID:The role of lipid peroxidation and calcium in galactosamine induced toxicity in the rat liver. 848 37

Ciprofibrate (CP), a peroxisome proliferator, has been shown to reduce rat liver endoplasmic reticulum (ER) Ca(2+)-ATPase activity both in vitro and in vivo. The ER Ca(2+)-ATPase is highly susceptible to thiol reactivity, and maintenance of maximal enzyme activity is critically dependent upon the integrity of these thiol groups. We therefore investigated whether CP alters ER Ca(2+)-ATPase thiol groups as a possible mechanism of enzyme inhibition. Using a thiol immunoblot technique, free thiol groups specifically on the ER Ca(2+)-ATPase were localized. Exposure of freshly isolated rat liver microsomes to CP (500 microM) resulted in a loss of sulfhydryl reactivity on the ER Ca(2+)-ATPase protein at 107 kDa, as identified using the thiol immunoblot assay. However, when rat liver microsomes were exposed to CP in the presence of reduced glutathione (GSH), thiol groups on the ER Ca(2+)-ATPase were protected. Also, the reduction of ER Ca(2+)-ATPase activity by CP could be ameliorated by co-incubation of rat liver microsomes with GSH. These observations indicate that CP reduces rat liver ER Ca(2+)-ATPase activity through interactions with free thiol groups located on this enzyme.
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PMID:Alteration of rat liver endoplasmic reticulum Ca(2+)-ATPase thiol integrity by ciprofibrate, a peroxisome proliferator. 851 90

The copper-glutathione complex (Cu(I)-GSH) efficiently acted in vitro as the source of Cu(I) in the reconstitution of apoceruloplasmin. Copper was found to reinstate in the various sites in a multistep process, with metal entry into the protein in a first phase, and a second step involving conformational changes of the protein leading to the recovery of the native structural and functional properties. This latter phase was found to be strongly facilitated by Mg2+ or Ca2+ and by ATP. Both Mg2+ and ATP had to be present for optimal reconstitution. These results may shed some light on the mechanisms governing the biosynthesis of ceruloplasmin in vivo. Cu(I)-GSH was the only complex able to reconstitute ceruloplasmin at neutral pH. Glutathione may thus function to shuttle the metal from the membrane copper pump, as the Wilson disease ATPase, and ceruloplasmin in the secretory compartments of the cell. The finding that ceruloplasmin acquires the native conformation after metal entry through a complex pathway triggered by Mg2+ and ATP suggests that they may act as physiological modulators of this process in vivo.
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PMID:Reconstitution of ceruloplasmin by the Cu(I)-glutathione complex. Evidence for a role of Mg2+ and ATP. 856 46

The level of malondialdehyde (MDA), an index of lipid peroxidation, and the antioxidants superoxide dismutase (SOD) and glutathione (GSH), as well as the activity of Na+, K(+)-ATPase, were assessed in whole rat brain after immobilization, anemic hypoxia (NaNO2) and 72 h starvation. The effect of these stressors on plasma glucose and corticosterone levels was also observed. Hypoxia and starvation stimulated the lipid peroxide formation in brain as indicated by an increase in the level of MDA, being higher after starvation than hypoxia. Brain SOD activity was also increased in response to hypoxia and starvation while GSH content was only diminished in hypoxia. However, neither MDA nor antioxidants were affected by immobilization. On the other hand, the activity of brain Na+, K(+)-ATPase was significantly increased by immobilization and hypoxia but decreased in starvation. A similar pattern of change was also observed in plasma glucose and corticosterone levels in response to these stressors. These results elucidate differences in the biochemical response of animals towards various types of stress, with increased lipid peroxide formation in hypoxia and starvation.
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PMID:Effect of various stressors on the level of lipid peroxide, antioxidants and Na+, K(+)-ATPase activity in rat brain. 862 Sep 36


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