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)

Treatment of phosphorylating fragments of bacterial membrane from Micrococcus lysodeikticus with trypsin leads to increase ATPase activity. As a result of this treatment, the membrane fragments acquire the ability to transform the ATP energy into transmembrane difference in potential. Dithiothreitol has a similar effect to that of trypsin on the membrane fragments from M. lysodeikticus. Dicyclohexylcarbodimide inhibits ATPase of the membrane fragments of M. lysodeikticus, and also the ATPase-reaction-coupled generation of membrane potential. It has been suggested that the increased ATPase activity of membranes from M. lysodeikticus during treatment with trypsin and dithiothreitol is connected with the effect of these agents on the protein inhibitor of ATPase.
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PMID:Membrane-reversible H+-ATPase from Micrococcus lysodeikticus. 0 6

The purpose of this study was to determine the effects of diamide, a reversible sulfhydryl oxidizing agent, on the transport of serotonin (5-HT) by mouse platelets. Diamide produced a concentration-dependent (10-200 microM) stimulation of 5-HT transport that was rapid and sustained over 0-10 minutes of incubation. When platelets were incubated with diamide (10-200 microM) in the presence of glucose, the content of reduced glutathione was significantly decreased only at a final concentration of 200 microM, while washed platelets incubated with diamide (10-200 microM), in the absence of glucose, had a significant concentration-dependent decrease in their content of reduced glutathione. Fluoxetine, an inhibitor of the platelet 5-HT transporter, blocked diamide-induced stimulation of 5-HT transport. The kinetics of 5-HT transport showed that diamide caused a marked increase in the maximal rate of transport (Vmax control = 28.4 +/- 1.4 vs. Vmax diamide = 60.9 +/- 4.1 pM/10(8) platelets/4 min) but did not significantly alter the Km values. Ouabain, an inhibitor of platelet Na(+)-K+ ATPase, blocked the stimulation by diamide in a concentration-dependent manner. Dithiothreitol, a disulfide reducing agent, was able to partially reverse the stimulation of platelet 5-HT transport caused by diamide. This study has shown that diamide can stimulate the active transport of 5-HT by mouse platelets and suggests a possible role for free sulfhydryl groups in the regulation of this process.
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PMID:Stimulation of the active transport of serotonin into mouse platelets by the sulfhydryl oxidizing agent diamide. 133 56

In view of the potential role of free radicals in the genesis of cardiac abnormalities under different pathophysiological conditions and the importance of contractile proteins in determining heart function, this study was undertaken to examine the effects of oxygen free radicals on the rat heart myofibrils. Xanthine plus xanthine oxidase (X + XO) which is known to generate superoxide anions (O2-) and hydrogen peroxide (H2O2), an activated species of oxygen, was found to decrease Ca(2+)-stimulated ATPase activity, increase Mg(2+)-ATPase activity and reduce sulfhydryl (SH) group contents in myofibrils; these effects were completely prevented by superoxide dismutase (SOD) plus catalase (CAT). Both H2O2 and hypochlorous acid (HOCl), an oxidant, produced actions on cardiac myofibrils similar to those observed by X + XO. The effects of H2O2 and HOCl were prevented by CAT and L-methionine, respectively. N-ethylmaleimide (NEM) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), inhibitors of SH groups, also produced effects similar to those seen with X + XO. Dithiothreitol (DTT), a well known sulfhydryl-reducing agent, prevented the actions of X + XO, H2O2, HOCl, NEM and DTNB. These results suggest that marked changes in myofibrillar ATPase activities by different species of oxygen free radicals may be mediated by the oxidation of SH groups.
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PMID:Alterations in cardiac contractile proteins due to oxygen free radicals. 164 33

The effects of several guanine nucleotide analogues on (Na+,K+)-ATPase activity of membranes isolated from several tissues were analyzed to determine if a G-protein might be involved in the hormonal regulation of the (Na+,K+)-ATPase. Submillimolar concentrations of GTP gamma S, but not GMPPNP, inhibit rat skeletal muscle and axolemma, but not kidney, (Na+,K+)-ATPase activity. Furthermore, GDP beta S does not reverse GTP gamma S inhibition, but rather itself slightly inhibits (Na+,K+)-ATPase activity. Dithiothreitol can block and reverse GTP gamma S inhibition of skeletal muscle (Na+,K+)-ATPase; the results obtained with axolemma membranes are complicated by the inhibition of (Na+,K+)-ATPase activity in these membranes by DTT. Results showing that high membrane concentrations can mute the inhibitory action of GTP gamma S suggest that a minor contaminant in GTP gamma S preparations is responsible for inhibiting (Na+,K+)-ATPase activity. Neither vanadate, a heavy metal, GDP, phosphate, nor thiophosphate, however, is responsible for this inhibition, and the inhibitory activity elutes with GTP gamma S from Sephadex G-10 columns. It is concluded that GTP gamma S or a structural derivative of GTP gamma S inhibits the (Na+,K+)-ATPase, in a tissue-specific manner, not by interaction with a G-protein as a GTP analogue, but through a direct chemical interaction with the (Na+,K+)-ATPase or some regulatory protein. The terminal SH group of the nucleotide analogue is probably required for this interaction.
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PMID:Thiophosphoryl guanine nucleotide analogues inhibit the (Na+,K+)-ATPase. 164 90

Treatment of rat brain slices with veratrine and monensin decreased (Na+ + K+)-ATPase activity in the membranes in a dose-dependent manner. The effect of monensin, like that of veratrine, was accompanied by a decrease of maximal binding sites for ouabain. The inhibitory effect of monensin on the enzyme activity was dependent on external Ca2+ at low concentrations, but not at a high concentration. The decreased enzyme activity induced by monensin was restored by subsequent incubation of the slices in a Ca(2+)-free medium containing 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (BAPTA-AM), a chelator of intracellular Ca2+. The effect of monensin at a low concentration on enzyme activity was antagonized by amiloride (1 mM), bepridil (5 microM), quinacrine (30 microM) or verapamil (30 microM), but not by nifedipine (1 microM) or omega-conotoxin (1 microM). Furthermore, the inhibitory effect of monensin at a high concentration under Ca(2+)-free conditions was blocked by BAPTA-AM (30 microM) and by bepridil (100 microM) or diazepam (500 microM), inhibitors of mitochondrial Na(+)-Ca2+ exchange. Inhibitors of calmodulin, protein kinase C, phospholipase A2 and calpain did not affect the monensin-induced decrease of enzyme activity. Dithiothreitol (10 mM) blocked the effect of monensin on enzyme activity but did not affect the ionophore-induced influx of Ca2+ in the slices.
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PMID:Na+ influx-induced decrease of (Na+ + K+)-ATPase activity in rat brain slices: role of Ca2+. 166 55

Cardiac contractile activity is usually controlled by intracellular Ca2+, but it can also be modified by oxidizing agents. Incubation of guinea pig heart myofibrils with diamide (3 mM, 1 h) increased basal (no Ca2+) ATPase activity by 580% and abolished Ca2+ dependence. The effect was proportional to diamide concentration (0.01-1 mM) and duration of preincubation (up to 2 h). Dithiothreitol (5 mM, 1 h) reversed most of the basal ATPase activation and restored Ca2+ sensitivity. Other sulfhydryl reagents produced a similar effect but also produced inhibition of total ATPase. In intact cell preparations, diamide produced a slow tonic contraction, consistent with myofibril activation. In the perfused rat heart, 1 mM diamide slowly increased diastolic ventricular pressure; this increase was partially reversed by dithioerythritol. In isolated rat heart myocytes, 1 mM diamide produced a slow tonic contraction, increased contractility in response to stimulation. Cardiocytes superfused for 1 h with buffer containing EGTA to deplete Ca2+ did not contract in response to stimulation but showed a slow tonic contraction with diamide. This contraction could be slowly and only partially reversed by dithioerythritol. Response to stimulation was restored by addition of Ca2+. The results show that diamide can produce contraction in viable cells. This contraction does not require extracellular Ca2+ and is unlikely to involve intracellular Ca2+. The direct activation of myofibrillar ATPase may contribute to the increased myocardial stiffness seen in ischemia and to ischemic contracture.
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PMID:Reversible elimination of myofibrillar Ca2+ sensitivity by diamide and other sulfhydryl reagents: comparison with reversible contracture produced in intact cells. 214 65

Dithiothreitol-dependent MgATP2- and Mg-ADP- hydrolytic activities owing to nucleoside triphosphate hydrolase were examined kinetically in tachyzoite cells of five strains of Toxoplasma gondii with various virulence. The tachyzoites of all the strains were revealed to have a high ATP and ADP hydrolytic potency. The value of Vmax and Km obtained from each strain indicated that there were two classified types of T. gondii about ATP and ADP hydrolysis. The most virulent strain (RH) and avirulent strain (Fukaya) were classified in a type with higher ATPase than ADPase activities. Two virulent strains (C56, Beverley) and an avirulent strain (ME49) were classified in the other type with the same activities of ATPase and ADPase.
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PMID:Remarkable activities of nucleoside triphosphate hydrolase in the tachyzoites of both virulent and avirulent strains of Toxoplasma gondii. 214 44

A Cl(-)-stimulated ATPase activity, which is sensitive to both N-ethylmaleimide and p-chloromercuribenzenesulfonate, has been localized to the basolateral membrane of Aplysia enterocytes. Dithiothreitol reversed the inhibition of Cl(-)-stimulated ATPase induced by p-chloromercuribenzenesulfonate. These results suggest that surface sulfhydryl ligands of the ATPase participate in the catalytic activity of the enzyme.
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PMID:Inhibition of Cl(-)-stimulated ATPase activity in isolated basolateral membranes from Aplysia gut. 215 44

Hydrogen gas production was observed to occur during ATP-driven H+/K+ exchange in anaerobically grown E. coli. Neither process was found in aerobically grown cells or anaerobic cells grown on nitrate medium or when the osmotic pressure was decreased or K+ removed, or finally when DCCD, arsenate or CCCP was applied. Dithiothreitol restored the process even in the presence of CCCP but not in other cases of inhibition. A model of a multienzyme transport super-complex is proposed. The supercomplex consists of three genetically independent mechanisms: F0F1 H+-ATPase to provide energy, the K+-transporting Trk system as energy sink and formate-hydrogen lyase as donor of reducing equivalents. Within this supercomplex direct transduction of energy is accomplished via oxidation of 2 SH to S-S.
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PMID:Formation of an ion transport supercomplex in Escherichia coli. An experimental model of direct transduction of energy. 246 24

Omeprazole, believed to inhibit H+, K+-ATPase, was used to study acid secretion dynamics in isolated gastric mucosa. Tissue was mounted in a chamber and continuously supplied with both fresh nutrient and secretory solution (flow-through). Acid secretion was monitored on and recorded by a pH-stat microprocessor set-up. In spontaneously secreting mucosa the continuous presence of omeprazole causes a monotonic decline in secretion rate to a new lower steady state. The relationship between the inhibited steady-state acid secretion rate and omeprazole concentration is expressed by the sum of two hyperbolic functions with K1s differing by a factor of more than 100. When omeprazole is removed, the secretion rate always recovers. The amount of acid suppressed depends uniquely on omeprazole exposure: it is proportional to the exposure at low exposure and disproportionate (logarithmic) at high exposure. The index of conservation declines with omeprazole exposure, i.e. the inhibition by omeprazole ranges from conservative (no net loss of acid) to non-conservative (net loss of acid). Dithiothreitol causes the inhibition by omeprazole to be conservative (index of conservation = 0) at even higher omeprazole exposure. The index of conservation was introduced to allow for numerical evaluation of both inhibitory and stimulatory effects regardless of the magnitude of the effect. It is concluded that omeprazole acts at two different sites, possibly with inhibition by sulphoxide derivatives on the formation step and sulphide derivatives on the translocation step.
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PMID:Omeprazole: inhibitor of both acid formation and translocation in gastric mucosa. 261 61


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