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

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.
...
PMID:Gastric secretion. 1 82

Binding studies of various nucleotides to the purified coupling factor-latent ATPase from Mycobacterium phlei have been carried out using gel filtration, equilibrium dialysis, and ultrafiltration methods. The purified latent ATPase binds 3 mol of ADP per mol of the enzyme with an apparent dissociation constant of 68 muM. Binding of nucleotides occurred in the decreasing order: ADP, epsilon-ATP, epsilon-ADP, UDP, adenyl-5'-yl imidodiphosphate (AMP-P(NH)P), IDP, and adenosine 5'-(alpha,beta-methylene)diphosphate (AdoP(CH2)P). AMP-P(NH)P inhibits both soluble (Ki = 77 muM) and membrane-bound latent ATPase activity. However, AMP-P(NH)P does not affect oxidative phosphorylation in membrane vesicles of M. phlei. AMP-P(NH)P exhibits one binding site per molecule of the enzyme with a dissociation constant of 71 muM. After trypsin treatment of the enzyme, the binding of ADP decreases 35%, while AMP-P(NH)P binding remains unchanged. Moreover, AMP-P(NH)P binding was not displaced by ADP. Studies with sulfhydryl agents showed that, in contrast to AMP-P(NH)P, binding of at least 1 mol of ADP requires the participation of sulfhydryl groups. The results indicate that AMP-P(NH)P and ADP do not share a common binding site and that the latent ATPase enzyme has separate sites for ATP hydrolysis and ATP synthesis.
...
PMID:Binding of nucleotides to purified coupling factor-latent ATPase from Mycobacterium phlei. 1 31

The effects of acid on fragmented sarcoplasmic reticulum from rabbit white skeletal muscle have been studied. Brief exposure of sarcoplasmic reticulum membranes to pH values in the range 5.5 to 6.0 at 37 degrees caused rapid inactivation of calcium accumulation measured at 25 degrees in the presence of oxalate (calcium uptake) while (Ca2+, Mg2+)-ATPase (EC 3.6.1.3) activity was enhanced by 75%. ATPase activity, measured at 37 degrees in the absence of oxalate and in the calcium steady state, was unaltered when calcium uptake was inactivated. Calcium efflux from sarcoplasmic reticulum vesicles, previously loaded passibely with 45CaCl2, was only slightly increased when calcium uptake was abolished. At still lower pH values, 5.0 to 5.5, (Ca2+, Mg2+)-ATPase was inactivated while Mg2+ ATPase was more acid-resistant. Acid inactivation of calcium uptake followed simple first order kinetics for at least 80% of the time course. The rate constant, k, increased from 0.043 min-1 to 1.63 min-1 between pH 6.50 and pH 5.35. At pH 4.65, Ea, the energy of activation, was 31 kcal mol-1 between 24 degrees and 43 degrees. Inactivation, once initiated, was irreversible. Aged suspensions of sarcoplasmic reticulum were more sensitive to acid inactivation. Ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid enhanced inactivation, and calcium specifically protected against inactivation with half-maximal effect at 1 to 2 mM. The sulfhydryl reagent, dithiothreitol (1 mM), caused significantly increased rates of inactivation. Calcium binding was studied by dual wavelength spectrophotometry and stopped flow analysis. Acid inactivation distinguished two ATP-induced binding sites, previously described (Entman, M. L., Snow, T. R., Freed, D., and Schwartz, A. (1973) J. Biol. Chem. 248, 7762-7772) as a superficial Mg2+-independent Site A which binds and releases calcium rapidly and a deeper Mg2+-dependent Site B which binds and releases calcium more slowly. Rates of binding to both sites were decreased by acid inactivation. Binding of calcium to Site A increased, however, from 4.6 to 6.4 nmol mg of protein-1 whereas that to Site B decreased from 17.0 to 6.9 nmol mg of protein-1. Passive binding of calcium to sites of medium affinity (K = 7 X 10(4) M-1) was unaffected by acid inactivation of calcium uptake. Temperature dependence of (Ca2+, Mg2+)-ATPase was unchanged in the range 9-34 degrees. Above 34 degrees, the higher activation energy process (Ealpha = 33.7 kcal mol-1) observed in control sarcoplasmic reticulum and thought to arise from a conformational change in the ATPase (Inesi, G., Millman, M., and Eletr, S. (1973) J. Mol. Biol. 81, 483-504) was diminished by acid inactivation (Ealpha = 8.2 kcal mol-1) in a manner suggesting that it is related to active calcium transport. The ATP in equilibrium 32Pi exchange reaction was diminished by acid, but 25% of the activity remained when calcium uptake was completely abolished...
...
PMID:Proton inactivation of Ca2+ transport by sarcoplasmic reticulum. 1 42

The effects of monovalent cations on calcium uptake by fragmented sarcoplasmic reticulum have been clarified. Homogenization of muscle tissue in salt-containing solutions leads to contamination of this subcellular fraction with actomyosin and mitochondrial membranes. When, in addition, inorganic cations are contributed by the microsomal suspension and in association with nucleotide triphosphate substrates there is an apparent inhibition of the calcium transport system by potassium and other cations. However, when purified preparations were obtained after homogenization in sucrose medium followed by centrifugation on a sucrose density gradient in a zonal rotor, calcium uptake and the associated adenosine triphosphatase activity were considerably activated by potassium and other univalent cations. When plotted against the log of the free calcium concentration there was only a slight increase in calcium uptake and ATPase activity in the absence of potassium ions but sigmoid-shaped curves were obtained in 100 mM K+ with half-maximal stimulation occurring at 2 muM Ca2+ for both calcium uptake and ATPase activity. The augmentation in calcium uptake was not due to an ionic strength effect as Tris cation at pH 6.6 was shown to be inactive in this respect. Other monovalent cations were effective in the order K+ greater than Na+ greater than NH4+=Rb+=Cs+ greater than Li+ with half-maximal stimulation in 11 mM K+, 16 mM Na+, 25 mM NH4+, Rb+, and Cs+ and in 50 mM Li+. There was nos synergistic action between K+ AND Na+ ions and both calcium uptak and associated ATPase were insensitive to ouabain. Thallous ions stimulate many K+-requiring enzymes and at one-tenth the concentration were nearly as effective as K+ ions in promoting calcium uptake. The ratio of Ca2+ ions transported to P1 released remained unchanged at 2 after addition of K+ ions indicating an effect on the rate of calcium uptake rather than an increased efficiency of uptake. In support of this it was found that during the stimulation of calcium uptake by Na+ ions there was a reduction in the steady state concentration of phosphorylated intermediate formed from [gamma-32P]ATP. It is considered that there is a physiological requirement for potassium ions in the relaxation process.
...
PMID:Caclium uptake and associated adenosine triphosphatase activity in fragmented sarcoplasmic reticulum. Requirement for potassium ions. 1 56

Dicyclohexylcarbodiimide-resistant mutants of Escherichia coli were isolated and characterized In one mutant the unc genes and affects the membrane-integrated part of the ATP synthetase. The sensitivity of ATP synthetase functions to N,N' -dicyclohexylcarbodiimide was compared in wild-type and mutant membranes. The membrane-integrated part of the wild-type ATP synthetase is highly sensitive to ATP-dependent membrane energization and restoration of lactate-dependent energization of ATPase-depleted membranes. In mutant membranes this concentration has only a slight effect on these activities whereas a severe inhibition is obtained at 200 muM. Using the highly water-soluble 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide theactivities of wild-type and mutant membranes are inhibited to the same extent. TheATP synthetase of wild-type and mutant was partially purified and incorporated muM. Uinto liposomes. These showed an uncoupler-sensitive ATP-32Pi exchange and ATP-dependent quenching of acridine-dye fluorescence. The activities of mutant and wild-type proteoliposomes exhibit the same pattern of sensitivity to dicyclohexylcarbodiimide as the corresponding membranes.
...
PMID:A mutant ATP synthetase of Escherichia coli with an altered sensitivity to N,N' -dicyclohexylcarbodiimide: characterization in native membranes and reconstituted proteoliposomes. 1 31

I-protein inhibited theMg-activated ATPase [EC 3.6.1.3] activity of actinomyosin by approximately 50% at low ionic strength. Concomitantly, the onset of superprecipitation was retarded. I-protein was found to bind to myosin, but not to F-actin. The inhibitory action of I-protein occurred only in the absence of Ca ions in the troponintropomyosin-actin myosin system. Addition of Ca ions abolished the effect. Thus, it is very likely that I-protein prevents unnecessary hydrolysis of ATP in the relaxed state of muscle.
...
PMID:I-protein, a new regulatory protein from vertebrate skeletal muscle. III. Function. 1 32

The kinetic properties of the [3H]ADP-ATP exchange reaction catalyzed by Na+, K+-dependent ATPase [EC 3.6.1,3] were investigated, using NaI-treated microsomes from bovine brain, and the following results were obtained. 1. The rates of the Na+-dependent exchange reaction in the steady state were measured in a solution containing 45 micronM free Mg2+, 100 mMNaCl, 80 micronM ATP, and 160 micronM ADP at pH 6.5 and 4-5 degrees. The rate and amount of decrease in phosphorylated intermediate on adding ADP, i.e., the amount of ADP-sensitive EP, were measured while varying one of the reaction parameters and fixing the others mentioned above. Plots of the exchange rate and the amount of ADP-sensitive EP against the logarithm of free Mg2+ concentration gave bell-shaped curves with maximum values at 50-60 micronM free Mg2+. Plots of the exchange rate and the amount of ADP-sensitive EP against pH also gave bell-shaped curves with maximum values at pH 6.9-7. They both increased with increase in the concentration of NaCl to maximum values at 150-200 mM NaCl, and then decreased rapidly with increase in the NaCl concentration above 200 mM. The dependences of the exchange rate and the amount of ADP-sensitive EP on the concentration of ADP followed the Michaelis-Menten equation, and the Michaelis constants Km, for both were 43 micronM. The dependence of the exchange rate on the ATP concentration also followed the Michaelis-Menten equation, and the Km value was 30 micronM. The amount of ADP-sensitive EP increased with increase in the ATP concentration, and reached a maximum value at about 5 micronM ATP. 2. The N+-dependent [3H]ADP-ATP exchange reaction was started by adding [3H]ADP to EP at low Mg2+-concentration. The reaction consisted of a rapid initial phase and a slow steady phase. The amount of [3H]ATP formed during the rapid initial phase, i.e. the size of the ATP burst, was equal to that of ADP-sensitive EP, and was proportional to the rate in the steady state. At high Mg2+ concentration, the rate of Na+-dependent exchange in the steady state was almost zero, and EP did not show any ADP sensitivity. However, rapid formation of [3H]ATP was observed in the pre-steady state, and the size of the ATP burst increased with increase in the KCl concentration. From these findings, we concluded that an enzyme-ATP complex (E2ATP) formed at low Mg2+ concentration is in equilibrium with EP + ADP, that the rate-limiting step for the exchange reaction is the release of ATP from the enzyme-ATP complex, that the ADP-insensitive EP (formula: see text) produced at high Mg2+ concentration is in equilibrium with the enzyme-ATP complex, and that the equilibrium shifts towards the enzyme-ATP complex on adding KCl. Actually, the ratio of the size of the ATP burst to the amount of EP was equal to the reciprocal of the equilibrium constant of step (formula: see text), determined by a method previously reported by us.
...
PMID:Kinetic studies on the ADP-ATP exchange reaction catalyzed by Na+, K+-dependent ATPase. Evidence for the K.S.T. mechanism with two enzyme-ATP complexes and two phosphorylated intermediates of high-energy type. 1 33

The UV absorption difference spectrum of heavy meromyosin induced by ATP was measured at various temperatures. At higher temperatures, the difference spectrum formed rapidly after adding ATP and continued steadily during the steady state which we have called the ATP-form of difference spectrum. At lower temperatures, the ATP-form of difference spectrum decayed into the other form before the steady state was attained. This was identical to the difference spectrum obtained by adding ADP and has been called the ADP-form of difference spectrum. At intermediate temperatures, biphasic decay was observed. The results indicate that the dominant intermediate at the steady state is altered from the one showing the ATP-form of difference spectrum at higher temperatures to that showing the ADP-form at lower temperatures. The population of the two intermediates depends on the temperature between the two extremes. This temperature-induced transition was observed in the presence of any divalent cation such as Mg2+, Mn2+, or Ca2+. A similar transition was observed with the difference spectrum induced by ITP in the presence of MgCl2. The pH dependence of the single early decay of the ATP-induced difference spectrum was measured in the presence of MnCl2 at 1 degree. The apparent rate constant of the decay showed a biphasic pH dependence, having the same shape as the pH activity curve of ATPase [EC 3.6.1.3] observed at higher temperatures. The rate determining step for the steady state ATPase at higher temperatures is thought to be the step of changing from the intermediate complex showing the ATP-form of difference spectrum to that showing the ADP-form. This is inconsistent with our previous mechanism (Yazawa, M. et al. (1973) J. Biochem. 74, 1107-1117). The rate determining step at lower temperatures was assigned as a step of ADP dissociation.
...
PMID:Temperature dependence of the decay of the UV absorption difference spectrum of heavy meromyosin induced by adenosine triphosphate and inosine triphosphate. 1 41

1. A stable ATPase [EC 3.6.1.3] complex (TF0-F1) from the thermophilic bacterium PS3 was reconstituted into vesicles capable of energy transformation,measured as ATP-dependent enhancement of fluorescence of 8-anilinonoaphthalene-1-sulfonate. 2. The factors necessary for obtaining highly active vesicles were investigated. Cholate and deoxycholate were both required for solubilization of TF0-F1 and P-lipids, and removal of the detergents by dialysis resulted in vesicle formation. Medium of around pH 8 and low ionic strength containing 2.5 mM MgSO4 was found suitable for dialysis. The optimal temperature for reconstitution was 30 degrees with soybean P-lipids and 45 degree with PS3 P-lipids. The optimal ratio of protein to lipid was about 1/50. 3. The vesicles obtained under these conditions were mainly 100-200 nm in diameter, covered with 9.5 nm spheres, and had a bouyant density of 1.06 in sucrose andan internal volume of about 0.5 mul per mg of P-lipids.
...
PMID:Reconstitution of vesicles capable of energy transformation from phospholipids and adenosine triphosphatase of a thermophilic bacterium. 1 54

The existence of nonadrenergic, noncholinergic nerve components in the autonomic nervous system is now well established. They are strongly represented in the gastrointestinal tract of all vertebrates and have been identified in a variety of other organs, including lung, trachea, bladder, esophagus, eye, seminal vesicles, and possibly parts of the vascular and central nervous systems. Their ultrastructural identification and transmission properties are known and their physiological role is beginning to be understood, at least in the gastrointestinal tract. Evidence that ATP is the transmitter released from nonadrenergic, noncholinergic (purinergic) nerves includes: (a) synthesis and storage of ATP in nerves; (b) release of ATP from the nerves when they are stimulated; (c) exogenously applied ATP mimicking the action of nerve-released transmitter, both producing a specific increase in K+ conductance; (d) the presence of Mg-activated ATPase, 5'nucleotidase, and adenosine deaminase, enzymes, which inactivate ATP; (e) drugs (including 2-substituted imidazolines, 2,2'-pyridylisatogen and dipyridamole), that produce similar blocking or potentiating effects on the response to exogenously applied atp and nerve stimulation.
...
PMID:Purine nucleotides. 1 17


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---