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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)

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.
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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.
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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.
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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 pH-activity curve of heavy meromyosin ATPase [EC 3.6.1.3] was measured at various temperatures. The pH-activity curve at higher temperatures showed a maximum at low pH and a minimum at pH 7 to 8 as has been already reported. At lower temperatures it was sigmoidal in shape, similar to a simple dissociation curve of pKa 6 to 7. The pH-activity curve at intermediate temperatures appeared to be inbetween the two extreme shapes. These changes in pH-activity curve with temperature were found to be common in the presence of divalent cations such as Mg2+, Mn2+, and Ca2+. The ATPase mechanism may be identical in the presence of any divalent cation, and the rate determining step revealing the steady state rate alters by changing the temperature. The transition temperatures estimated at pH 8 were 10 degrees, 8 degrees, and about 5 degrees in the presence of MnCl2, CaCl2, and MgCl2, respectively. The difference in the temperature coefficients above and below the transition temperature was most distinct in the presence of MnCl2, and vague in the presence of CaCl2. A similar change of pH-activity curve with temperature was found with heavy meromyosin ITPase in the presence of MgCl2.
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PMID:Temperature induced transition of the pH-activity curve of heavy meromyosin adenosine triphosphatase and inosine triphosphatase. 1 40

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.
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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.
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PMID:Reconstitution of vesicles capable of energy transformation from phospholipids and adenosine triphosphatase of a thermophilic bacterium. 1 54

The effect of an inhibitor of adenylate cyclase (ACI) was measured on some enzymes associated with cyclic nucleotide-regulated metabolism. Soluble guanylate cyclase was inhibited; both soluble and particulate cyclic GMP-phosphodiesterases were stimulated. Cyclic AMP phosphodiesterases were unaffected. In contrast, the activities of Na, K-ATPase, protein kinase, phosphorylase kinase, glycogen synthetase and a number of glycosidases were not altered by equipotent amounts of the inhibitor. It is concluded that this substance acts as a modulator of both cyclic AMP and cyclic GMP metabolism in heart and other tissues.
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PMID:The effect of adenylate cyclase inhibitor (ACI) on guanylate cyclase, phosphodiesterase and other enzymes in heart. 1 79

(Na+K)-activated ATPase activity from gills of yearling spring chinook was examined using a new rapid assay method. Characterization of the enzyme activity was performed. Optimal activity was obtained at pH 7.2 in the presence of 240 mM NaCl, 120 mM KCl, 20 mM MgCl2 and 10 mM Na2ATP. Maximal inhibition of the enzyme was observed in the presence of 0.5 mM ouabain. Differential centrifugation indicated that 75% of the enzymatic activity was sedimented at 1000 x g. Only 8% of the activity was found in the microsomal pellet. Treatment with 0.1% sodium deoxycholate liberated activity from the 1000 x g pellet and elevated the activity. This treatment caused a loss of 20% of the original activity of the preparation. Statistical analysis of the sampling procedure for gill (Na+K)-activated ATPase activity indicated that there was small variation in the technique itself when compared to variation between the individual gill arches and between individual fish. Results indicate that for meaningful comparisons of groups of fish, the sampling of the gill arches must be standardized and a large number of individual fish must be sampled.
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PMID:Characterization of gill (Na + K)-activated adenosine triphosphatase from chinook salmon, Oncorhynchus tshawytscha. 1 43

31P nuclear magnetic resonance spectra at 145.7 MHZ were obtained of concentrated suspensions of E. coli cells. The position of the Pi resonance was used to determine the pH, and in most experiments it was possible to distinguish the intracellular (pHin) and extracellular (pHex) values. During respiration pHin approached 7.55, while pHex varied from 6.0 to 8.0. With succinate as a carbon source and in a N2 environment, pHin - pHex. Upon addition of glucose, pHin greater than pHex. In the presence of an ATPase (adenosinetriphosphatase; ATP phosphohydrolase; EC 3.6.1.3) inhibitor dicyclohexylcarbodiimide, pHin remained equal to pHex even in the presence of glucose. In other experiments, oxygenation brought pHin above pHex even in the presence of dicyclohexylcarbodiimide. These experiments are consistent with Mitchell's hypothesis that, first, delta pH can be created by the reversal of the ATPase reaction and, second, that protons are pumped outward during respiration. In addition to Pi, about 10 more resonances were resolved, several of which were assigned to different phosphate metabolites.
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PMID:High-resolution 31P nuclear magnetic resonance studies of metabolism in aerobic Escherichia coli cells. 1 57

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.
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PMID:Purine nucleotides. 1 17


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