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)

We have undertaken the analytical fractionation of epithelial cells from toad urinary bladder, a tissue extensively used to study epithelial transport of ions and water. In an attempt to establish markers for the main subcellular organelles, a number of enzymes were assayed in cell homogenates. The nearly ubiquitous plasma membrane marker 5'-nucleotidase, and the transferases that donate N-acetylglucosaminyl, galactosyl, and sialyl residues to glycoproteins and glycolipids in the Golgi complex were not detectable. Glucose-6-phosphatase activity was low in relation to that of nonspecific phosphatases and, therefore, not suitable for identifying the endoplasmic reticulum. Like the cytosolic enzyme lactate, dehydrogenase, catalase was essentially found in the high-speed supernatant, with a noteworthy part of aminopeptidase (substrate, leucyl-beta-naphthylamide) and NAD glycohydrolase. Other enzymes, including cytochrome c oxidase, acid phosphatase, acid N-acetyl-beta-glucosaminidase, alkaline phosphatase, alkaline phosphodiesterase I, nucleoside diphosphatase (substrate ADP), oligomycin-resistant Mg++-ATPase, and mannosyltransferase (acceptor, dolichylphosphate) were fairly active and largely sedimentable. After differential centrifugation, cytochrome oxidase, acid phosphatase, and acid N-acetyl-beta-glucosaminidase were typically associated with the large granule fraction, whereas the other sedimentable enzymes exhibited a broad distribution profile overlapping the nuclear, large granule, and microsome fractions. Their behavior in density equilibrium centrifugation is examined in a companion paper.
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PMID:Subcellular fractionation of epithelial cells from toad urinary bladder. 1. Assay of marker enzymes and differential centrifugation. 250 71

We have studied lipid peroxidation and Ca2+-ATPase activity of the porcine intestinal brush-border membranes using a oxygen-radical-generating system consisting of dithiothreitol (DTT)/Fe2+ and tert-butyl hydroperoxide (t-BuOOH). The rates of lipid peroxidation were measured by formation of thiobarbituric acid-reactive substances (TBAR) and conjugated diene. Incubation of the membranes with DTT/Fe2+ in the absence and presence of t-BuOOH resulted in a slight (about 20%) and a marked (about 50%) inhibition of Ca2+-ATPase activity, respectively. The degree of inhibition was dependent on the hydroperoxide concentration. Addition of thiourea effectively protected Ca2+-ATPase activity but catalase and superoxide dismutase showed a slight and no effect on protection of the ATPase activity, respectively. Results of kinetic studies on the ATPase activity with varying ATP and Ca2+ concentrations revealed that the decrease in the enzyme activity by treatment with these oxidizing agents is mainly due to decrease of the Vmax value. Modification of SH groups in the membrane proteins by thiol group reagents such as N-ethylmaleimide, monoiodoacetate and monoiodacetamide did not induce the inhibition of Ca2+-ATPase activity. From these results, it is suggested that inhibition of the ATPase activity of the membranes by treatment with DTT/Fe2+ in the presence and absence of t-BuOOH is dependent on lipid peroxidation and that oxidative modification of SH groups may not be directly involved to the loss of the ATPase activity. In addition, results of the fluorescence anisotropy measurements of pyrene-labeled membranes suggested that change in the Ca2+-ATPase activity is partly related to a decrease in the membrane lipid fluidity.
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PMID:Effect of lipid peroxidation on membrane-bound Ca2+-ATPase activity of the intestinal brush-border membranes. 252 63

Although oxygen free radicals have been implicated as mediators of cellular injury in myocardial ischemia-reperfusion, the exact nature of defects produced by these radicals is not clear. Because sarcolemmal Ca2+-pump is involved in the efflux of Ca2+ from the cell, this study was undertaken to examine the effects of oxygen free radicals on sarcolemmal ATP-dependent Ca2+ accumulation and Ca2+-stimulated Mg2+-dependent adenosinetriphosphatase (ATPase) activities as well as lipid peroxidation of membrane phospholipids. Isolated rat heart sarcolemmal membranes were incubated with xanthine + xanthine oxidase [a superoxide anion radical (O2-)-generating system], H2O2, or H2O2 + Fe2+ [a hydroxyl radical (HO.)-generating system] and assayed for Ca2+-pump activities. O2- inhibited the Ca2+-pump activities in a time-dependent manner; a significant inhibition of Ca2+-stimulated ATPase activity was seen after 1 min of incubation. Superoxide dismutase showed a protective effect on depression in Ca2+-pump activities caused by O2-.H2O2 inhibited Ca2+-pump activities in a dose-dependent manner; this inhibition was protected by the addition of catalase. HO. depressed the Ca2+-pump activities to a greater extent in comparison with H2O2. Mannitol showed a protective effect on HO.-induced inhibition of Ca2+-pump activities. The promotion of lipid peroxidation by free radicals was evident from increased formation of malondialdehyde. These results indicate that the sarcolemmal membrane is altered on exposure to oxygen free radicals, and this may result in depressing the Ca2+-pump mechanism for Ca2+ efflux from the myocardial cell.
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PMID:Depression of heart sarcolemmal Ca2+-pump activity by oxygen free radicals. 253 32

Low activity of catalase, superoxide dismutase, alterations in metabolism of glutathione as well as activation of lipid peroxidation and increase in Na+, K+-ATPase activity were found in erythrocytes of newborns funic blood under conditions of chronic hypoxia and simultaneous effects of acute and chronic hypoxia. Acute hypoxia during labor caused increase in activity of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, Na+, K+-ATPase as well as in the rate of lipid peroxidation. These alterations, observed in the enzymatic activity and in the rate of lipid peroxidation, which were detected in funic blood erythrocytes under conditions of hypoxia, may be responsible for some diseases during postnatal period of children ontogenesis.
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PMID:[Status of the antioxidant system of erythrocytes in newborn infants in acute and chronic hypoxia]. 254 43

Hydrogen peroxide inhibition of maximum Ca2+-ATPase and Na+,K+-ATPase activity was measured in a membrane-enriched preparation of rabbit lens cortical fibers and epithelium. At 5 X 10(-6) M hydrogen peroxide maximum Ca2+-ATPase activity was inhibited by 39%, while maximum Na+,K+-ATPase activity was stimulated. Ca2+-ATPase activity was almost completely inhibited at 5 X 10(-4) M hydrogen peroxide, in comparison to Na+,K+-ATPase activity, which was only inhibited by 28% at a concentration of hydrogen peroxide an order of magnitude larger. The addition of catalase to hydrogen peroxide-pretreated samples did not reverse the inhibition of Ca2+-ATPase by hydrogen peroxide.
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PMID:Oxidative inhibition of Ca2+-ATPase in the rabbit lens. 254 47

To understand the involvement of changes in sulfhydryl groups in causing depression of the sarcolemmal Ca2+-pump activities, this study was undertaken to examine the effects of oxygen free radicals on rat heart sarcolemmal sulfhydryl groups, Ca2+-stimulated adenosinetriphosphatase (ATPase), and ATP-dependent Ca2+ accumulation. In addition, the effects of sulfhydryl reagents such as dithiothreitol, cysteine, and N-ethylmaleimide on Ca2+-pump activities were investigated. The inhibition of sarcolemmal Ca2+-pump activities by O2-. (xanthine + xanthine oxidase) and H2O2 was decreased by the addition of dithiothreitol or cysteine in a dose-dependent manner. N-ethylmaleimide also showed inhibitory effects on Ca2+-pump activities both in a dose- and time-dependent manner; dithiothreitol and cysteine prevented changes in Ca2+-pump activities because of N-ethylmaleimide. Heart sarcolemmal sulfhydryl groups were depressed by O2-., H2O2, and .OH (H2O2 + Fe2+) both in a dose- and time-dependent manner. Superoxide dismutase, catalase, and D-mannitol showed protective effects on the sulfhydryl group depression by O2-., H2O2, and .OH, respectively. A significant correlation between changes in sarcolemmal Ca2+-stimulated ATPase activity and sarcolemmal sulfhydryl groups was seen. These results indicate that oxygen free radicals may depress the heart sarcolemmal Ca2+-pump activities by modifying the sulfhydryl groups in the sarcolemmal membrane.
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PMID:Mechanism for depression of heart sarcolemmal Ca2+ pump by oxygen free radicals. 255 Nov 90

A study was made of the erythrocytic membranes in patients with stage II-III metabolic and alimentary obesity. The red blood cells may serve as model of the membranes of other cells of the internal organs, that is why their changes are likely to mirror the total impairment of the function of the cell membranes in the illness under consideration. The patients' red blood cells were characterized by high permeability, increased ATPase activity, catalase activation, reduction of the content of the thiol groups, and by the displacement of the thiol-disulfide balance towards oxidized forms. A correlation was discovered between the elevation of red blood cell permeability and red blood cell K+, Na+-ATPase activation. The changes in the thiol-disulfide balance brought about inconclusive shifts in the magnitude of permeability, in the activity of ATPase isoenzymes, and in the content of cholesterol fractions in red blood cells of patients with metabolic and alimentary obesity. The changes thus discovered are of paramount importance for understanding the pathogenesis of metabolic abnormalities associated with obesity and for rational treatment of this patients' group.
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PMID:[New data on characteristics of the chemism of erythrocytes in patients with metabolic-alimentary obesity]. 280 Apr 51

The results of our experiments demonstrated that one hour of ischemia followed by one hour of reflow in the kidney caused a reduction in (Na+K+)ATPase activity and microsomal sulfhydryl content as well as an increase in microsomal lipid peroxidation. Renal venous malondialdehyde concentration was increased soon after reperfusion of the ischemic kidney. All these changes were rectified by an infusion of 0.123 mmol N-(2-mercaptopropionyl)glycine/kg over a 70 min period. On the other hand, an in vitro addition of 0.01-0.5 mM N-(2-mercaptopropionyl)glycine to a membrane preparation in the presence of H2O2 and Fe3+ did not prevent but rather potentiated the free radical effect on the enzyme activity. However, addition of superoxide dismutase alone or with catalase together with 2-MPG were effective in preventing the enzyme depression induced by H2O2. The results therefore indicate that free radical generation participates in the evolution of ischemia/reperfusion cell injury and thiol-reducing agents may be beneficial in alleviating the cell damage in vivo.
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PMID:Effects of N-(2-mercaptopropionyl)glycine on ischemic-reperfused dog kidney in vivo and membrane preparation in vitro. 283 50

The generation of superoxide radicals from xanthine oxidase-hypoxanthine in a particulate fraction of gerbil cerebral cortex influenced the activity of the synaptic enzyme adenylate cyclase, as well as Mn2+- and Na+,K+-sensitive forms of ATPase. Low concentrations of xanthine oxidase actually elevated the sensitivity of adenylate cyclase to GTP, GTP + norepinephrine (NE), and forskolin but not significantly to Mn2+. Higher levels of xanthine oxidase elicited a marked inhibition of these responses. The stimulation of adenylate cyclase mechanisms requiring GTP (GTP, forskolin, and NE) was more susceptible than was Mn2+, suggesting that the guanine nucleotide stimulatory protein was more vulnerable to free radical attack than the catalytic site of adenylate cyclase. Superoxide dismutase (SOD), but not catalase, partially protected the forskolin-sensitive enzyme from the action of xanthine oxidase-hypoxanthine. A combination of SOD plus catalase preserved enzyme responses to forskolin. In comparison, additions of SOD plus mannitol or catalase plus flunarizine were less effective. The sensitivity of the particulate ATPase to Mn2+ was more labile to the consequence of superoxide formation than Na+, K+ -ATPase. In this regard the Ca2+,Mg2+ sensitivity of the enzyme was reduced only to a marginal extent. The findings might be analogous to in vivo data in which cerebral adenylate cyclase and Na+, K+-ATPase are damaged following postischemic reperfusion in gerbils, a process thought to be mediated by free radicals.
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PMID:Free radicals generated by xanthine oxidase-hypoxanthine damage adenylate cyclase and ATPase in gerbil cerebral cortex. 285 Apr 58

The association of an ATPase with the yeast peroxisomal membrane was established by both biochemical and cytochemical procedures. Peroxisomes were purified from protoplast homogenates of the methanol-grown yeast Hansenula polymorpha by differential and sucrose gradient centrifugation. Biochemical analysis revealed that ATPase activity was associated with the peroxisomal peak fractions which were identified on the basis of alcohol oxidase and catalase activity. The properties of this ATPase closely resembled those of the mitochondrial ATPase of this yeast. The enzyme was Mg2+-dependent, had a pH optimum of approximately 8.5 and was sensitive to N,N'-dicyclohexylcarbodiimide (DCCD), oligomycin and azide, but not to vanadate. A major difference was the apparent Km for ATP which was 4-6 mM for the peroxisomal ATPase compared to 0.6-0.9 mM for the mitochondrial enzyme. Cytochemical experiments indicated that the peroxisomal ATPase was associated with the membranes surrounding these organelles. After incubations with CeCl3 and ATP specific reaction products were localized on the peroxisomal membrane, both when unfixed isolated peroxisomes or formaldehyde-fixed protoplasts were used. This staining was strictly ATP-dependent; in controls performed in the absence of substrate, in the presence of glycerol 2-phosphate instead of ATP, or in the presence of DCCD, staining was invariably absent. Similar staining patterns were observed in subcellular fractions and protoplasts of Candida utilis and Trichosporon cutaneum X4, grown in the presence of ethanol/ethylamine or ethylamine, respectively.
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PMID:A proton-translocating adenosine triphosphatase is associated with the peroxisomal membrane of yeasts. 288 51


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