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)

An HCO-3-activated and SCN--inhibited ATPase (ATP phosphohydrolase, EC 3.6.1.3) found in homogenates of intestinal mucosa of the eel was solubilized by Triton X-100. Optimal HCO-3-concentration and pH for the enzyme were 25 mM and 8.7, respectively. HCO-3-ATPase activity in both homogenate and solubilized preparations increased after seawater adaptation. This adaptive increase in enzyme activity was also observed in the gills and the kidney. The HCO-3-ATPase seems to be related to transport mechanisms, especially for Cl-, in osmoregulatory surfaces of the eel.
Biochim Biophys Acta 1976 Sep 14
PMID:HCO-3-activated adenosine triphosphatase in intestinal mucosa of the eel. 0 50

Cardiac myosin from thyrotoxic animals (myosin-T) exhibits elevated Ca2+ -ATPase activity which is resistant to further stimulation by sulfhydryl modification. In the present study, we have compared the enzymatic properties of myosin-T with those of myosin from euthyroid rabbits (myosin-N) and the derivatives of myosin-T and myosin-N formed by blocking the most rapidly reacting class of thiols (SH1) with N-ethylmaleimide (NEM). Vmax for Ca2+ -ATPase of myosin-T was about 250% greater than myosin-N and was nearly the same as NEM-modified myosin-N. Values for the apparent Km of myosin-T and NEM-modified myosin-N were 200% greater than the value for unmodified myosin-N. Vmax and Km for K+ (EDTA)-ATPase activity of NEM-modified myosin-T and myosin-N were identical. The Ca2+ saturation, pH, and salt-dependency curves for the ATPase activity of myosin-T were parallel to the curves for myosin-N and differed from those for the NEM-modified myosins. Myosin-T exhibited an increased rate of hydrolysis of ATP, CTP, and UTP in both low (0.05m) and high (0.5m) KCl medium. NEM-modified myosin-N showed increased hydrolysis of ATP and CTP in low KCl medium and increased hydrolysis of ATP, CTP, and UTP in high KCl medium. These results support the hypothesis that the enzymatic behavior of myosin-T may be caused by an alteration in the active site near the SH, thiols. The unique enzymatic properties of myosin-T did not seem to be the result of a major change in structure. The electrophoretic pattern of light chains from myosin-T and myosin-N was the same in polyacrylamide gels containing either 8 M urea at pH 8.6 or sodium dodecyl sulfate. Also, myosin-T had a normal amino acid composition and lacked 3-methyl-histidine and hot acid-stable phosphate.
Circ Res 1976 Sep
PMID:Enzymatic properties of native and N-ethylmaleimide-modified cardiac myosin from normal and thyrotoxic rabbits. 0 19

Oxidative phosphorylation in Escherichia coli membrane vesicles with a right-side-out orientation and loaded with ADP was investigated. Substrates of the electron transport chain could energize the phosphorylation of ADP, with the order of effectiveness being D-lactate greater than reduced phenazinemethosulfate greater than succinate greater than reduced nicotinamide adenine dinucleotide. Inhibitors of D-lactate oxidation, proton conductors, and inhibitor of the Mg2+ATPase (EC 3.6.1.3) all inhibited oxidative phosphorylation when coupled to D-lactate oxidation. ATP synthesis was absent in membrane vesicles prepared from a mutant strain lacking the Mg2+ATPase. Valinomycin or nigericin partially inhibited oxidative phosphorylation in the presence of potassium. Valinomycin plus nigericin completely inhibited ATP synthesis. The effect of various agents on the respiration-dependent establishment of a transmembrane pH gradient was also examined. NaCN and carbonyl cyanide p-trifluoromethoxyphenylhydrazone inhibited the establishment of a pH gradient while dicyclohexylcarbodiimide had no effect. These results are in good agreement with a chemiosmotic model for oxidative phosphorylation.
J Biol Chem 1976 Sep 10
PMID:Oxidative phosphorylation in right-side-out membrane vesicles from Escherichia coli. 0 60

The 13S coupling factor of oxidative phosphorylation from Alcaligenes faecalis has a latent adenosine triphosphatase (ATPase) function that can be activated by heating at 55 degrees C for 10 min at pH 8.5 in 50% glycerol. The specific activity increases from 0.1 to 20--30 mumol min-1 mg-1. Adenosine 5'-triphosphate (ATP) is not required for stabilization at 55 degreesC when glycerol is present. Activation involves displacement of the endogenous ATPase inhibitor subunit (epsilon subunit), and readdition of this subunit results in deactivation. In the deactivation process the ATPase inhibitor subunit can be replaced by other cationic proteins such as protamine, histones, or poly(lysine). Mg2+ and H+ also are effective deactivators. The fact that every positively charged substance tested deactivated the enzyme suggests that the inhibitor subunit is complexed with the enzyme at a site containing a surplus of negative charges. The activated enzyme is not labile, but it is salt labile, having a half-life of 2-3 min in 0.1 M KI at either 25 or 0 degrees C. The activated ATPase is also inhibited by aurovertin, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD), and by the cross-linking agent dimethyl suberimidate. Evidence for polymorphism comes from finding that the properties of the unactivated enzyme (intrinsic ATPase) are different in many ways from the properties of activated ATPase. With respect to the coupling factor's ability to hydrolyze ATP, the data in this study suggest that there are at least four distinct functional allomorphs of this enzyme: (1) the latent enzyme, which has no kinetically measurable ATPase activity, (2) intrinsic ATPase, which is catalyzed by a small percentage of the molecular population that has been activated by some natural mechanism, (3) activated ATPase, which has properties different from those of intrinsic ATPase, and (4) aged activated ATPase, in which some of the properties (Km for substrate, sensitivity to deactivation by Mg2+ and H+) spontaneously change within 30 min.
Biochemistry 1976 Sep 21
PMID:Molecular polymorphism and mechanisms of activation and deactivation of the hydrolytic function of the coupling factor of oxidative phosphorylation. 0 31

A density gradient-purified microsomal membrane preparation from rabbit fundic gastric mucosa was used for a detailed study of the K+-stimulated ATPase and associated intermediate reactions. Membranes incubated with gamma-[32P]ATP show the rapid incorporation of 32P into phosphoprotein. Phosphoprotein levels were markedly reduced (1) when ATP hydrolysis went to completion or (2) upon addition of unlabeled ATP, thus suggesting the participation of a rapid turnover phosphorylated intermediate in the gastric microsomal ATPase. Addition of K+, Rb+ or Tl+ greatly reduced the level of the intermediate while stimulating ATPase activity; the observed affinities of these cations were similar for the effects on both ATPase and intermediate levels, with Tl+ greater than K+ greater than Rb+. Neither ATPase nor intermediate were stimulated by Na+, and ouabain was without effect on the reactions, thus differentiating this system from the (Na+ + K+)-ATPase. Addition of various inhibitors showed differential effects on the partial reactions of the gastric ATPase system. N-ethylmaleimide and Zn2+ showed characteristics of completely abolishing the K+-stimulated component of ATPase as well as the effects of K+ in reducing the level of intermediate, thus suggesting that these agents exert their inhibitory effect on a phosphoprotein phosphatase partial reaction. F- abolished the K+-stimulated ATPase, but its more complex effects on the intermediate suggested an additional reaction step within the domain of the phosphorylated intermediate. Results are consistent with a model system for the gastric microsomal ATPase involving a Mg2+-dependent protein kinase, a phosphorylated intermediate(s), and a K+-stimulated phosphoprotein phosphatase.
Biochim Biophys Acta 1976 Sep 07
PMID:Studies on the phosphorylated intermediates of a K+-stimulated ATPase from rabbit gastric mucosa. 0 43

The procedure for the isolation of the highly active fraction of sarcoplasmic reticulum from pigeon and dog hearts is described. The method is based on the partial loading of heart microsomes with calcium and oxalate ions and the precipitation of loaded vesicles in sucrose and potassium chloride concentration gradients. Preparations obtained possess high activity of Ca2+-dependent ATPase and are also able to accumulate up to 10 mumol Ca2+ per mg protein. Purification of sarcoplasmic reticulum membranes is accompanied by a decrease in concentration of cytochrome a+a3 and an increase in the content of [32P]phosphoenzyme. The basic components in "calcium-oxalate preparation" from hearts are proteins with molecular weights of about 100000 (Ca2+-dependent ATPase) and 55000 Calcium-oxalate preparation from pigeon hearts was used for subsequent purification of Ca2+-dependent ATPase. Specific activity of purified enzyme from pigeon hearts is 12-16 mumol Pi/min per mg protein. Enzyme activity of purified Ca2+-dependent ATPase is inhibited by EGTA and is not sensitive to azide, 2,4-dinitrophenol and ouabain. The data obtained demonstrate the similarity of calcium pump systems and Ca2+-dependent ATPases isolated from heart and skeletal muscles.
Biochim Biophys Acta 1976 Sep 07
PMID:Isolation of calcium pump system and purification of calcium ion-dependent ATPase from heart muscle. 0 44

Membrane vesicles from Azotobacter vinelandii O prepared by osmotic lysis of spheroplasts in tris (hydroxymethyl) aminomethane/acetate buffer (pH 7.8) contain a latent adenosine triphosphatase (ATPase). The ATPase can be activated when the vesicles are incubated in the presence of an electron donor (D-lactate) and a mixture of adenosine diphosphate and inorganic phosphate or by controlled treatment with trypsin. After the ATPase is activated, the membrane vesicles in the presence of adenosine triphosphate accumulate calcium but not glucose or rubidium (in the presence of valinomycin). ATP-dependent calcium uptake follows Michaelis-Menten kinetics with a Km of 48 muM and a Vmax of 20 nmol/min/mg of membrane protein and is highly specific for calcium over cations magnesium, barium, lanthanum, sodium, potassium, and lithium. The calcium accumulated in the presence of ATP is freely exchangeable with external calcium and is rapidly released in the presenceof uncouplers or ATPase inhibitors. Calcium uptake in the presenceof ATP is blocked by dicyclohexylcarbodiimide, ADP, p-chloromercuriphenylsulfonate, by the proton-conducting ionophores m-chlorophenylcarbonylcyanide hydrazone, nigericin, monensin, and gramicidin D, but not by potassium cyanide, anoxia, or valinomycin (in the presence of potassium). Measurements of the external pH of vesicle suspensions reveal that protons are actively taken up by the membranes during hydrolysis of ATP. These results suggest that vesicles prepared under these conditions have a topology which is inverted with respect to the intact cell and that calcium is accumulated by means of proton antiport.
J Biol Chem 1976 Sep 25
PMID:ATP-dependent calcium transport in isolated membrane vesicles from Azotobacter vinelandii. 0 92

A method is described for the preparation of high purity myosin from the left ventricle of pig heart. The purified myosin was free from nucleic acid, actin, tropomyosin, troponin, the 150,000 molecular weight protein and other contaminants. Analyses of subunits in the purified myosin were carried out on 3.5% acrylamide gel with 0.1% SDS. Of the total protein present in myosin, 11.3% was in the light chains; light chain 1 (LC1), 5.9% and light chain 2 (LC2), 5.4%. Urea gel electrophoresis of the purified myosin showed three closely spaced bands corresponding to the 20,000 dalton, the charge-modified 20,000 dalton and the phosphorylated 20,000 dalton components. The properties of the Ca2+-activated and K+-activated ATPases [EC 3.6.1.3] of the purified myosin were also studied. The Km values were 27 and 55 muM and the Vmax values were 0.263 and 0.317 mumole P1/mg/min for the Ca2+-activated and K+-activated ATPases, respectively. The pH-activity profiles and the effects of SH modification were of the skeletal myosin type except that the activities were lower.
J Biochem 1976 Sep
PMID:Cardiac myosin from pig heart ventricle. Purification and enzymatic properties. 1 Feb 92

1. Guanylate cyclase of every fraction studied showed an absolute requirement for Mn2+ ions for optimal activity; with Mg2+ or Ca2+ reaction was barely detectable. Triton X-100 stimulated the particulate enzyme much more than the supernatant enzyme and solubilized the particulate-enzyme activity. 2. Substantial amounts of guanylate cyclase were recovered with the washed particulate fractions of cardiac muscle (63-98%), skeletal muscle (77-93%), cerebral cortex (62-88%) and liver (60-75%) of various species. The supernatants of these tissues contained 7-38% of total activities. In frog heart, the bulk of guanylate cyclase was present in the supernatant fluid. 3. Plasma-membrane fractions contained 26, 21, 22 and 40% respectively of the total homogenate guanylate cyclase activities present in skeletal muscle (rabbit), cardiac muscle (guinea pig), liver (rat) and cerebral cortex (rat). In each case, the specific activity of this enzyme in plasma membranes showed a five- to ten-fold enrichment when compared with homogenate specific activity. 4. These results suggest that guanylate cyclase, like adenylate cyclase, and ouabain-sensitive Na+ + K+-dependent ATPase (adenosine triphosphatase), is associated with the surface membranes of cardiac muscle, skeletal muscle, liver and cerebral cortex; however, considerable activities are also present in the supernatant fractions of these tissues which contain very little adenylate cyclase or ouabain-sensitive Na+ + K+-dependent ATPase activities.
Biochem J 1976 Sep 01
PMID:Guanylate cyclase. Subcellular distribution in cardiac muscle, skeletal muscle, cerebral cortex and liver. 1 Aug 90

1. The membrane-integrated portion (TF0) of the proton translocating ATPase complex (TF0-F1) of the thermophilic bacterium PS3 was highly purified. Its proton-conducting activity was investigated in vesicles reconstituted from TF0 and phospholipids (TF0 vesicles). 2. The rate of proton conduction through TF0 was proportional to the membrane potential imposed (6H+ uptake/s/TF0 molecule with 103 mV at pH 8.0). The pH profile of the rate revealed that a proton, not a hydroxy ion, was the true substrate conducted and that there was a monoprotic proton binding site in TF0 (pKa = 6.8). The temperature coefficient of proton conductance of TF0 showed a considerable variation depending on the phospholipids of the vesicles with respective transition temperatures. 3. Passive proton conduction through TF0 was inhibited stoichiometrically by addition of either the soluble ATPase portion (TF1) of TF0-F1, or an energy transfer inhibitor dicyclohexylcarbodiimide or an antibody against TF0. 4. The proton conductance of TF0 was concluded to represent its intrinsic activity in the original TF0-F1 complex.
J Biol Chem 1977 Sep 10
PMID:Purified proton conductor in proton translocating adenosine triphosphatase of a thermophilic bacterium. 1 67


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