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)

Phosphorylation of the ATPase dependent on Na+ and K+ is promoted through the synergistic action of cations on both sides of the membrane. This phenomenon has been observed in plasma membrane vesicles isolated from sheep-kidney outer medulla which accept ATP from the outside surface (inside-out) and which are tight for sodium ions. In these inside-out vesicles phosphorylating capacity is low even in the presence of 100 mM extravesicular sodium chloride as is turnover of the enzyme. The level of the phosphoenzyme and the transient release of inorganic phosphate from the phosphoenzyme increases several-fold when sodium chloride is allowed to equilibrate over the membrane, 25 mM intravesicular NaCl is necessary to obtain the half-maximum level of the phosphoenzyme. This result shows that intravesicular (= extracellular) low affinity sites are involved in the phosphorylation. Intravesicular potassium ions modify the activating action of Na+ on the phosphorylation by increasing the steady state of the phosphoenzyme at low intravesicular sodium ion concentrations. This suggests that Na+ and K+ compete with each other for the intravesicular cation-binding site.
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PMID:Effect of intravesicular monovalent cations on the steady state of the phosphoenzyme of adenosine triphosphatase dependent on sodium and potassium ions in inside-out plasma-membrane vesicles. 14 2

The oxidative phosphorylation and ATPase activity (initial and stimulated by DNP and Mg2+) in tumor mitochondria were investigated. The intact mitochondria of Zajdela hepatoma, in contrast to liver mitochondria, exhibit the ATPase activity which is slightly stimulated by 2,4-dinitrophenol and is markedly activated by Mg2+. The mitochondria from transplantable solid tumors (adenocarcinoma 755, Iensen sarcoma, sarcoma 45) despite satisfactory morphological integrity under electron microscopy are biochemically less intact than the mitochondria of hepatoma. ATPase of these mitochondria is also slightly stimulated by 2,4-dinitrophenol and significantly by Mg2+. The ATPase activity of thymus mitochondria, the normal tissue with sufficiently high proliferative activity, corresponds to that of tumor mitochondria. The total amount of enzyme in mitochondria of tumors investigated and thymus is not lowered, since the ATPase activity in the presence of both DNP and Mg2+ corresponds to the ATPase activity of liver mitochondria. The Mg2+ ATPase activity of tumor mitochondria is not sensitive or is only partly sensitive to oligomycin. The data obtained are indicative of a high lability of the phosphorylating system in tumor and thymus mitochondria. A possibility of reorganization of the energy mechanism of tumor mitochondria and some normal tissues in connection with increased metabolism requiring high energy consumption, is discussed.
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PMID:[Some peculiarities of ATPase in tumor mitochondria]. 15 49

This review has pointed out the good correlation frequently observed between ATPase activity of various contractile protein preparations and contractile function of various muscles including the myocardium. Some of the variables in the measurement of the various ATPases and the relationship of these measurements to physiological ATPase in the intact myofibril have been mentioned. The possible roles of changes in the light chains of sulfhydryl groups in the control of ATPase activity have been outlined. The possibility that phosphorylating reactions might exert control over physiological activity remains to be clarified. It is evident that, despite the large amount of research that has been done, our understanding of how the biochemistry of contractile proteins relates to physiological function is in its infancy, and only with a more complete elucidation of the underlying biochemistry of the components of contractile proteins of physiological and pathophysiological adaptations become evident.
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PMID:Cardiac contractile proteins. Adenosine triphosphatase activity and physiological function. 15 88

(1) Photophosphorylation, Ca2+-ATPase and Mg2+-ATPase activities of isolated chloroplasts were inhibited 55--65% when the chemical potential of water was decreased by dehydrating leaves to water potentials (psi w) of --25 bars before isolation of the plastids. The inhibition could be reversed in vivo by rehydrating the leaves. (2) These losses in activity were reflected in coupling factor (CF1) isolated from the leaves, since CF1 from leaves with low psi w had less Ca2+-ATPase activity than control CF1 and did not recouple phosphorylation in CF1-deficient chloroplasts. In contrast, CF1 from leaves having high psi w only partially recoupled phosphorylation by CF1-deficient chloroplasts from leaves havig low psi w. This indicated that low psi w affected chloroplast membranes as well as CF1 itself. (3) Coupling factor from leaves having low psi w had the same number of subunits, and the same electrophoretic mobility, and could be obtained with the same yields as CF1 from control leaves. However, direct measurements of fluorescence polarization, ultraviolet absorption, and circular dichroism showed that CF1 from leaves having low psi w differed from control CF1. The CF1 from leaves having low psi w also had decreased ability to bind fluorescent nucleotides (epsilon-ATP and epsilon-ADP). (4) Exposure of isolated CF1 to low psi w in vitro by preincubation in sucrose-containing media inhibited the Ca2+-ATPase activity of the protein in subsequent assays without sucrose. Inclusion of 5 or 10 mM Mg2+ in the preincubation medium markedly inhibited Ca2+-ATPase activity. (5) These results show that CF1 undergoes changes in cells which alter its phosphorylating ability. Since low cell psi w changed the spectroscopic properties but not other protein properties of CF1, the changes were most likely caused by altered confurn, photophosphorylation. The inhibition of ATPase activity in CF1 in vitro at low psi w and high ion concentration mimicked the change in activity seen in vivo.
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PMID:Conformation and activity of chloroplast coupling factor exposed to low chemical potential of water in cells. 15 20

Myosin isolated under phosphorylation conditions, showed an additional band of phosphorylated light chain. In the case of cardiac myosin, LC2 is the phosphorylated light chain whereas in skeletal myosin, it is the 18,000 dalton component known as DTNB light chain. There are no differences in K+-EDTA and Ca2+ activated myosin ATPase of cardiac and skeletal of control and phosphorylated myosins. Our experiments showed that the rat heart and skeletal muscle myosins isolated under phosphorylating conditions exhibited high phosphate content which is associated with higher actin activated Mg2+ ATPase activity of myosin as compared to control. Control myosin phosphorylated using myosin light chain kinase and Ca2+ also showed high actin activated myosin ATPase activity. Beef heart myosin isolated in the presence of phosphate buffer, also exhibited a higher level of phosphate followed by an increase in actin activation as compared to myosin isolated in the absence of phosphate buffer. All these experimental data suggest that there is a direct relationship between actin activation and the amount of phosphate incorporated as a result of phosphorylation.
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PMID:Phosphorylation and its effects on ATPase activity of cardiac and skeletal myosins. 16 48

Considerable progress has been made in recent years in our understanding of the phosphorylating apparatus in mitochondria, chloroplasts, and bacteria. It has become clear that the structure and the function of the ATP synthesizing apparatus in these widely divergent organisms is similar if not virtually identical. The subunit composition of F1, its molecular architecture, the location and function of substrate binding sites, as well as putative control sites, understanding of the component parts of the oligomycin-sensitive ATPase complex, and the role of these components in the function of the complex all are under active investigation in many laboratories. The developing information and the new insights provided have begun to permit experimental approaches, at the molecular level, to the mode of action of the ATPase in electron-transport-coupled ATP synthesis.
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PMID:Mitochondrial ATPase. 16 56

Changes in the adenine nucleotide metabolism after an oral glucose load were studied in the liver of normal and alloxan-diabetic rats. Changes in the energy charge were positively correlated with those in the blood glucose and plasma immunoreactive insulin levels. One hour after an oral glucose load when the plasma immunoreactive insulin levels increased maximally, the energy charge increased maximally from 0.846 to 0.867 (P less than 0.001). The increase in the energy charge was accompanied by a concomitant decrease in the ADP levels (P less than 0.05). The respiratory control ration, state 3 respiration per unit of cytochrome a (+a3), and DNP-induced ATPase activity per unit of cytochrome a (+a3) increased significantly. The adenylate kinase and pyruvate kinase activities in the liver remained unchanged. On the other hand, the energy charge in the liver of alloxan-diabetic rats did not increase significantly after an oral glucose load. It was suggested that an increase in the energy charge of the liver is attributable to the more rapid flux of intermediary metabolism in the enhanced ADP-phosphorylating reactions by mitochondria, owing to an elevated level of insulin available to the hepatic cells.
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PMID:Changes in adenylate energy charge of the liver after an oral glucose load. 17 25

Resting and active-state respiratory velocities, respiratory control, high amplitude volume changes, and latent ATPase activities were examined in hepatic mitochondria from rats fed 3'-methyl-4-dimethylaminoazobenzene (3'MeDAB) for production of liver tumors and from rats in three phases of liver regeneration subsequent to subtotal hepatectomies. Tetrabutylammonium bromide, a lipophilic probe capable of selectively inhibiting phosphorylating oxidation or uncoupling oxidation from phosphorylation, was used to detect subtle alterations in lipophilicity characteristics of the organelles and it was concluded that mitochondria from pre-hyperplastic, hyperplastic, and neoplastic tissues had a higher than normal degree of membrane lipophilicity at specific functional sites. Control of respiration by ADP was markedly augmented in all experimental groups; this behavior, plus depressed sensitivity to swelling agents and energized contraction, were similar in mitochondria from hepatomas and from 3-day regenerating livers. These mitochondrial functions were even more pronounced, however, in cells in pre-hyperplastic states (6 and 16 h subsequent to partial hepatectomy). Many forms of liver damage result in mitochondrial alterations which elevate the capacity for oxidative phosphorylation. Such changes associated with induction of azo dye oncogenesis are mimicked by the degree of hyperplasia in the tissue following the first mitotic wave of regeneration; implications relevant to hepatocarcinogenesis are discussed.
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PMID:Mitochondrial functional changes during hepatic hyperplasia and azo dye carcinogenesis. 17 55

A phosphorylation potential deltaGp, where deltaGp = deltaGo' + RT2.303 log ([ATP]/([ADP][Pi])), of approx. 44.3 kJ.mol-1 (10.6 kcal.mol-1) was generated by submitochondrial particles that were oxidizing either NADH or succinate. Addition of adenylyl imidodiphosphate, which should suppress adenosine triphosphatase activity of any uncoupled particles, did not raise the phosphorylation potential. Raising the Pi concentration slightly increased the magnitude of the value for [ATP]/[ADP], but this did not fully compensate for the increased Pi concentration, so that the phosphorylation potential decreased slightly as the Pi concentration was raised. The phosphorylation potential developed by submitochondrial particles is lower than that generated by phosphorylating membrane vesicles from some bacteria, and is also less than that developed externally by mitochondria, but is strikingly close to the phosphorylation potential that is generated internally by mitochondria.
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PMID:The phosphorylation potential generated by respiring bovine heart submitochondrial particles. 20 65

1. The magnitude of the protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans was estimated. The membrane potential component was determined from the uptake of S(14)CN(-), and the transmembrane pH gradient component from the uptake of [(14)C]methylamine. In each case a flow-dialysis technique was used to monitor uptake. 2. With NADH as substrate, the membrane potential was about 145mV and the pH gradient was below 0.5 pH unit. The membrane potential was decreased by approx. 15mV during ATP synthesis, and was abolished on addition of carbonyl cyanide p-trifluoromethoxyphenylhydrazone. In the presence of KCl plus valinomycin the membrane potential was replaced by a pH gradient of 1.5 units. 3. Succinate oxidation generated a membrane potential of approx. 125mV and the pH gradient was below 0.5 pH unit. Oxidation of ascorbate (in the presence of antimycin) with either 2,3,5,6-tetramethyl-p-phenylenediamine or NNN'N'-tetramethyl-p-phenylenediamine as electron mediator usually generated a membrane potential of approx. 90mV. On occasion, ascorbate oxidation did not generate a membrane potential, suggesting that the presence of a third energy-coupling site in P. denitrificans vesicles is variable. 4. With NADH or succinate as substrate, the phosphorylation potential (DeltaG(p)=DeltaG(0)'+RTln[ATP]/ [ADP][P(i)]) was approx. 53.6kJ/mol (12.8kcal/mol). Comparison of this value with the protonmotive force indicates that more than 3 protons need to be translocated via the adenosine triphosphatase of P. denitrificans for each molecule of ATP synthesized by a chemiosmotic mechanism. In the presence of 10mm-KNO(3) the protonmotive force was not detectable (<60mV) but DeltaG(p) was not altered. This result may indicate either that there is no relationship between the protonmotive force and DeltaG(p), or that for an unidentified reason the equilibration of SCN(-) or methylamine with the membrane potential and the pH gradient is prevented by NO(3) (-) in this system.
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PMID:The protonmotive force in phosphorylating membrane vesicles from Paracoccus denitrificans. Magnitude, sites of generation and comparison with the phosphorylation potential. 21 22


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