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)

Proton transport by the vanadate-sensitive ATPase in plasma membrane (PM) vesicles from the marine unicellular microalga Platymonas viridis was investigated. The ATP-dependent generation of delta pH across the membranes of PM vesicles was followed by the changes in the absorbance of the aminoacridine probe, Acridine orange. Na+ caused the decay of delta pH generated by the ATPase, the rate of the decay being dependent on the concentrations of Na+ added. The phenomenon was specific for Na+. Amiloride inhibited Na(+)-dependent delta pH decay. The experiments support the idea of a Na(+)-extruding mechanism (H(+)-translocating ATPase plus Na+/H+ antiporter) operating in the PM of marine alga Pl. viridis.
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PMID:H(+)-translocating ATPase and Na+/H+ antiport activities in the plasma membrane of the marine alga Platymonas viridis. 132 76

1. Purified (Na+ + K+)-ATPase was irreversibly inhibited upon exposure to hydrogen peroxide, the superoxide anion, and the hydroxyl radical. 2. Comparison of the SDS-gel electrophoretic patterns of the ATPase samples exposed to these oxidants revealed that inhibition occurred either without gross structural changes, or concomitant with fragmentation and cross-linking of the enzyme subunits. 3. The oxidant modified ATPase was also shown to be more susceptible to degradation by several proteolytic enzymes.
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PMID:(Na+ + K+)-ATPase: inactivation and degradation induced by oxygen radicals. 132 81

Cultured rabbit lenses were irradiated with UV (311 nm peak; 295-340 nm) for 30 to 60 min. The entire spectrum lies in the near-UV, the major component is UVB, with a minor portion (25%) of UVA, and is henceforth referred to as near-UV(B). Posterior irradiation caused no cataract and no significant ionic imbalances compared to anterior irradiation, which caused opacification and marked changes in sodium and calcium concentrations. Anterior irradiation also resulted in reduced Na/K-ATPase activity in the epithelium. ATPase activity was not immediately inhibited; rather, only after culture was enzyme activity reduced. The concentration of reduced glutathione (GSH) decreased rapidly in the epithelium and more slowly in the underlying lens fibers. Loss of GSH was more rapid and extensive when irradiation occurred in the presence of oxygen. Irradiation under anaerobic conditions resulted in opacification but was considerably less extensive than when irradiation of lenses occurred in the presence of 7% oxygen. Near-UV(B) damage following anaerobic irradiation and 20 hrs of culture resulted in an increase in sodium levels and loss of GSH; calcium levels were not significantly elevated. Since irradiation of tryptophan solutions produced small amounts of hydrogen peroxide, the possibility of hydrogen peroxide-mediated damage was investigated but no role could be substantiated. Peroxide detoxification by the epithelium of near-UV(B) cataracts was observed, as measured by its ability to eliminate hydrogen peroxide added as a bolus.
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PMID:Mechanisms involved in cataract development following near-ultraviolet radiation of cultured lenses. 132 94

Previously, gastric (H+/K+)-ATPase inhibitors such as 2 have been prepared as analogues of 1a on the presumption that the 3-carbethoxy substituent plays a key role in establishing the orientation of the 4-arylamino group. In this paper we explore further the contribution made to activity by the quinoline 3-substituent. We show that, for compounds bearing such a substituent, only a particular combination of properties provides high activity, both in vitro and as inhibitors of gastric acid secretion in vivo. The ability of the substituent to affect activity by restricting rotation about the Cquin-N bond through a combination of both a pi-electron withdrawal and hydrogen bonding is supported by the current study. However, high activity is only achieved if the effect of this group on the quinoline pK(a) is kept to a minimum. 3-Acyl substituents provide an optimum combination of electronic properties. From this series, compound 17c (SK&F 96067) was shown to be a potent inhibitor of histamine-stimulated gastric acid secretion after oral dosing in the Heidenhain pouch dog and was selected for further development and evaluation in man.
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PMID:Reversible inhibitors of the gastric (H+/K+)-ATPase. 3. 3-substituted-4-(phenylamino)quinolines. 132 34

Sphingomyelin liposomes and brain microsomes were oxidized by exposure to hydrogen peroxide and ferrous ion. Lipid peroxidation were measured by the formation of thiobarbituric acid- reactive substances (TBAR). Hydroxyl radical was detected using the spin- trapping technique. Incubation of sphingomyelin liposomes with H2O2-Fe2+ resulted in an increase in the formation of TBAR. Na(+)-K(+)-ATPase activity was markedly inhibited and the SH group content decreased during incubation of microsomes in the presence of H2O2-Fe2+. Sodium ferulate effectively inhibited TBAR formation, protected Na(+)-K(+)-ATPase activity and prevented the oxidative modification of SH groups. Spin-trapping experiments showed that sodium ferulate effectively scavenged the hydroxyl radicals.
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PMID:Effect of hydroxyl radical on Na(+)-K(+)-ATPase activity of the brain microsomal membranes. 133 Mar 32

Proton transport-coupled unisite catalysis was measured with the H(+)-ATPase from chloroplasts. The reaction was measured in the ATP hydrolysis direction under deenergized conditions and in the ATP synthesis direction under energized conditions. The equilibrium constant of the enzyme does not change upon energization, whereas the dissociation constants of substrates and products change by orders of magnitude. This indicates that the Gibbs free enthalpy derived from proton translocation is used to change binding affinities of substrates and products, and this results in synthesis of free ATP.
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PMID:Proton transport-coupled unisite catalysis by the H(+)-ATPase from chloroplasts. 133 Oct 40

Two different types of proton transporting ATPases, v-and p-type H(+)-ATPases engage in epithelial ion transport. Properties, function, molecular structure and distribution of these H(+)-ATPase (v-type) and H+, K(+)-ATPase (p-type) are summarized here. Intraorganellar spaces, such as lysosome, synapse, multivesicular body, are acidified by the vacuole-type H(+)-ATPases. Secretion of proton by some types of intercalated cells of kidney collecting tubules is due to H(+)-ATPase. Gastric proton secretion is due to H+, K(+)-ATPase. Proton secretion and absorption of potassium by distal colon is due to p-type ATPase.
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PMID:[H(+)-ATPase and H(+), K(+)-ATPase]. 133 68

Osteoclasts are primary cells responsible for bone resorption. The most characteristic feature of osteoclasts is the presence of ruffled borders and clear zones. The resorbing area under the ruffled border of osteoclasts is acidic, which favors dissolution of bone mineral. In bone-resorbing osteoclasts, hydrogen ions are provided by carbonic anhydrase II, which catalyzes the hydration of CO2 to H2CO3. Recently, it has been shown that the proton pump of the vacuolar H(+)-ATPase type exists in the ruffled border membranes of osteoclasts. Secretion of hydrogen ions by osteoclasts generates an equal amount of cytoplasmic base equivalents, principally as HCO3-. Osteoclasts have a chloride/bicarbonate exchanger, which normalizes the intracellular pH when osteoclasts actively resorb bone. In this paper, we review the mechanism of the acid secretion by osteoclasts.
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PMID:[Mechanism of acid production and secretion by osteoclasts]. 133 70

In most eukaryotic cells, vacuolar H(+)-ATPases (V-ATPases) are present primarily or exclusively in intracellular membrane compartments, functioning in the acidification of the endocytic and secretory vacuolar apparatus necessary for constitutive cell function. V-ATPases also participate in renal hydrogen ion secretion in both the proximal and distal nephron, residing at high concentrations on the plasma membrane, where they are regulated physiologically to maintain the acid-base balance of the organism. Recent experiments have begun to reveal how the kidney controls transcellular proton transport while still maintaining acidification of intracellular compartments. Control may occur by recruitment of proton pumps to or away from the plasma membrane. The proton-transporting plasma membrane of intercalated cells is a specialized apparatus that translocates the enzyme between an intracellular membrane pool and the plasma membrane in response to physiological stimuli. Regulation may also occur by changes in the kinetics of the V-ATPase. V-ATPases are a family of structurally similar enzymes which differ in the composition of specific subunits. Cytosolic regulatory enzymes present in renal cells may preferentially affect V-ATPases in selective membrane compartments.
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PMID:Biochemistry of the renal V-ATPase. 133 93

Ultrastructural effects of hydrogen peroxide (H2O2) on the sarcolemma of the isolated rat heart were investigated with transmission electron microscopy combined with biochemical, enzyme histochemical, and freeze fracture techniques. Three hundred microM H2O2 were continuously administered to the Langendorff perfused isolated rat hearts. A significant amount of lipid peroxidation associated with depressed Na-K-ATPase activity was observed after 15 minutes of H2O2 perfusion (Group I), and consequently the cell membrane permeability was greatly increased. When 2.5 mM,N'-diphenyl-1,4-phenylenediamine (DPPD), a potent antioxidant, was added to the perfusate, the lipid peroxidation was totally inhibited (Group II). DPPD prevented an increase in the cell membrane permeability. However, Na-K-ATPase activity was not restored by DPPD. Decreased cytochemical staining of Na-K-ATPase was associated with an increase in cell membrane permeability. H2O2 appears to affect, not only lipids but also, intramembranous proteins embedded in the cell membrane. The combined effects of H2O2 on the membrane lipid and proteins result in the formation of membranous blebs.
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PMID:Ultrastructural effects of hydrogen peroxide on the sarcolemma of rat heart. 133 86


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