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)

Ca2+ is a powerful inhibitor (Ki is congruent to 16 muM) of basal and prostaglandin E1 (PGE1)-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing); EC 4.6.1.1] activity in membranes obtained from homogenized human platelets. Ca2+ (but not the ionophore A23,187) decreased V(max) of the reaction without an effect on the Ks for ATP. Neither ATP nor PGE1 affected Ki for Ca2+. In intact platelets A23,187 induced Ca2+ influx and markedly inhibited PGE1-stimulated rise in adenosine 3':5'-cyclic monophosphate (cAMP) levels. Guanylate cyclase [GTP pyrophosphate-lyase (cyclizing); EC 4.6.1.2] activity was mainly found in the soluble fraction (greater than 90%). Both soluble and membrane bound enzymes were stimulated by Mn2+ and Ca2+ and inhibited by Zn2+. Adenylate and guanylate cyclase activity were both present in a membrane fraction cyclase activity were both present in a membrane fraction which contained Ca2+ activated ATPase activity, and accumulated Ca2+ from the medium in the presence of ATP and oxalate. Other evidence indicates that these membranes originated in large part from the dense tubular system of the platelets. It is proposed that concurrent inhibition of adenylate cyclase and stimulation of guanylate cyclase facilitates the direct initiating effect of Ca2+ on platelet secretion and aggregation.
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PMID:Interrelationships between Ca2+ and adenylate and guanylate cyclases in the control of platelet secretion and aggregation. 0 60

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.
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PMID:Studies on the phosphorylated intermediates of a K+-stimulated ATPase from rabbit gastric mucosa. 0 43

Properties of HCO--3-stimulated ATPase from rat heart muscle nuclei were studied. The maximal activity of HCO--3-ATPase was observed at concentration of bicarbonate 25 mM. The enzyme had a pH optimum at pH 8.0-8.5. Bicarbonate stimulated the ATPase activity only in presence of Mg2+, Mn2+ and Zn2+, Co2+, Cd2+ and Ca2+ were ineffective. NaCO3 and Na2SO3 at concentration 30 mM stimulated the nuclear ATPase activity by 20% and 81%, respectively. Anions N3--, scn--, clO--4, and I-- inhibited both Mg2+-ATPase and HCO--3-ATPase. HSO--3 and SO2--4 ions did not affect the nuclear ATPase activity.
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PMID:[Anion-sensitive nuclear ATPase of the rat heart]. 2 54

The activity of calcium-stimulated ATPase (E.C. 3.6.1.3) in homogenates of the secretory enamel organ of rat incisors was studied biochemically. ATP hydrolysis was estimated from the amount of inorganic phosphate liberated. An analysis of the total degradation of ATP was initially performed to ensure that the enzyme assays pertained to the original substrate, ATP, and were not influenced by reaction products formed. Standard incubations were run in tris-maleate buffer, pH 8.2, with 3 mM ATP, 3 mM Ca2+ and 0.5 mM R 8231 at 37 degrees C. The presence of R 8231 was necessary to inhibit nonspecific alkaline phosphatase. The calcium-stimulated ATPase was completely inhibited when heated at 55-60 degrees C for 5 min. The pH optimum was found to be 8.2. The hydrolysis was substantially dependent on Ca2+ and was fastest when the ATP:Ca2+ ratio was 1:1. High substrate concentrations inhibited the hydrolysis. The addition of 1 mM Zn2+ and Ni2+ to the incubation medium markedly inhibited the hydrolysis as did, though less strongly, p-hydroxymercuribenzoate, oligomycin, EDTA and ruthenium red. l-Cysteine, mercaptoethanol, iodoacetic acid and sodium azide were without effect. F- was without effect unless added to a final concentration above 15 mM to media where Ca2+ had first been allowed to react with ATP.
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PMID:Calcium-stimulated ATPase activity in homogenates of the secretory enamel organ in the rat. 2 89

The activity of ATPase was studied in highly purified rat liver and thymus cell nuclei, HCO3-, CO3(2-) and SO3(2-) stimulated nuclear ATPase in 1.5--2 times. HSO3- did not affect the enzyme activity, and NO3-, J-, ClO4-,F- and SCN- inhibited it. Bicarbonate increased V and decreased Ka for ATP. SCN- inhibited HCO3--ATPase activity non-competitively with respect to HCO3-. Mg2+-ATPase activity did not depend on pH, and HCO3-component of the activity was decreased under alkaline pH. Mg2+, Mn2+ and Co2+ increased the initial ATPase activity and helped its stimulation with HCO3-. Ba2+, Ni2+ and Zn2+ inhibited the ATPase activity, and Ca2+ did not affect it, Nuclear ATPase is sensitive to 2,4-dinitrophenol and DNAase. It is suggested that cell nuclei have their own H+-ATPase differing for some characteristics from mitochondrial H+-ATPase.
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PMID:[Investigation of adenosinetriphosphatase activity of rat liver and thymus cell nuclei]. 3 23

Purified chondrocytic alkaline phosphatase (orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1) from bovine fetal epiphyseal cartilage hydrolyzes a variety of phosphate esters as well as ATP and inorganic pyrophosphate. Optimal activities for p-nitrophenyl phosphate, ATP and inorganic pyrophosphate are found at pH 10.5, 10.0 and 8.5, respectively. The latter two substrates exhibit substrate inhibition at high concentrations. p-Nitrophenyl phosphate demonstrates decreasing pH optima with decreasng substrate concentration. Heat inactivation studies indicate that both phosphorolytic and pyrophosphorolytic cleavage occur at the same site on the enzyme. Mg2+ (0.1-10.0 mM) and Mn2+ (0.01-0.1 mM) show a small stimulation of p-nitrophenyl phosphate-splitting activity at pH 10.5. Levamisole, Pi, CN-, Zn2+ and L-phenylalanine are all reversible inhibitors of the phosphomonoesterase activity. Pi is a competitive inhibitor with a Ki of 10.0 mM. Levamisole and Zn2+ are potent non-competitive inhibitors with inhibition constants of 0.05 and 0.04 mM, respectively. The chondrocytic alkaline phosphatase is inhibited irreversibly by Be2+, EDTA, EGTA, ethane-1-hydroxydiphosphonate, dichloromethane diphosphonate, L-cysteine, phenyl-methylsulfonyl fluoride, N-ethylmaleimide and iodoacetamide. NaCL, KCL and Na2SO4 at 0.5-1.0 M inhibit the enzyme. At pH 8.5, the cleavage of inorganic pyrophosphate (pyrophosphate phosphohydrolase, EC 3.6.1.1) by the chondrocytic enzyme is slightly enhanced by low levels of Mg2+ and depressed by concentrations higher than 1mM. Ca2+ show only inhibition. Similar effects of Mg2+ and Ca2+ on the associated ATPase (ATP phosphohydrolase, EC 3.1.6.3) activity were observed. Arrhenius studies using p-nitrophenyl phosphate and AMP as substrates have accounted for the ten-fold difference in V in terms of small differences in both the enthalpies and entropies of activation which are 700 cal/mol and 2.3 cal/degree per mol, respectively.
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PMID:Enzymatic characterization of the chondrocytic alkaline phosphatase isolated from bovine fetal epiphyseal cartilage. 4 Jun 3

The Ca2+-sensitive ATPase (adenosine triphosphatase) of human erythrocyte membranes is activated, not only by Ca2+ ions, but also by a series of other bivalent metal ions including Sr2+, Ba2+, Mn2+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+ and Pb2+. The degree of activation is dependent on the radius of the ion rather than on its nature, in contrast with the dissociation constant of the enzyme--metal ion complex.
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PMID:Activation of membrane-bound high-affinity calcium ion-sensitive adenosine triphosphatase of human erythrocytes by bivalent metal ions. 12 84

The purpose of this investigation was twofold: (1) to identify and characterize the enzymatic ATP hydrolysis system of epithelial cilia, and (2) to develop a quantitative, biochemical test for the ciliotoxic cystic fibrosis (CF) factor based on inhibition of ATP utilization by ciliary preparations. Our rationale for selecting this system for CF factor analysis relates to the tight and essential mechanochemical coupling of functioning cilia. Using rabbit tracheal epithelium as the source, a high molecular weight (greater than 200,000) ATPase was identified, partially purified, and extensively characterized. The properties of this protein were similar to those observed in previous studies of others with flagellar and ciliary dynein (the motility-associated ATPase) isolated from microorganisms. Analysis of the pH profile revealed a broad range of high enzymatic activity between 6.5 and 9. Studies with potential cation activators showed that the enzyme is activated equally by either Ca2+ or Mg2+ in equimolar concentrations. No activation occurred in the presence of Zn2+, Na+, H+, or Na+ plus K+ and the effect of Mg2+ or Ca2+ was not inhibited by Na+, K+, or Na+ plus K+. The enzyme hydrolyzed Mg2+-containing solutions of UTP, CTP, and ADP at 51-54% the rate of ATP dephosphorylation, whereas Mg-deoxy-ATP was hydrolyzed 79% as effectively as ATP. Using a newly devised, analytical technique with [gamma-32P]ATP as the substrate, the ATP hydrolysis of various ciliary preparations from rabbit trachea and oyster gill (including motile suspensions) was monitored in the presence of sera from CF homo- and heterozygotes. Reproducible rates of ATP dephosphorylation averaging 27 nmol/min/mg protein were demonstrable with homogenates of ciliated epithelium. None of the test systems evaluated, however, were capable of demonstrating CF-related differences in ATPase activity or ATP utilization. Although these attemps have been unsuccessful thus far, the approach described in this report provides an example of an objective, quantitative, biochemical assessment of ciliary function.
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PMID:Determination and characterization of ciliary ATPase in the presence of serum from cystic fibrosis patients. 12 30

Rat spermatozoa from the cauda epididymidis were found to have a lower activity of the surface ATPase than the spermatozoa from the caput region. The enzyme from spermatozoa of both regions had the same Michaelis constant (Km) for ATP of 5 X 10(-4) M. It was partly inhibited by ouabain and fluoride, but strongly inhibited by Cu2+, Zn2+,p-chloromercuribenzoate, 8-anilino-1-naphthalenesulphonate Triton X-100, Lubrol-PX, urea, guanidine hydrochloride, sodium dodecyl sulphate and glycerylphosphorylcholine. The enzyme of the spermatozoa from the cauda epididymidis was more sensitive to inhibition by ouabain and fluoride but less sensitive to inhibition by Cu2+ than that of the cells form the caput region. The Arrhenius plot of the temperature dependence of enzymatic activity varied for the cells from the caput and cauda epididymidis. The differences in the enzyme properties of spermatozoa from the two regions of the epididymis suggested that the decline in the activity during epididymal maturation may reflect changes in the lipids and sulphydryl groups of the sperm membrane.
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PMID:Changes in surface ATPase of rat spermatozoa in transit from the caput to the cauda epididymidis. 13 82

The purification of p protein to homogeneity from Escherichia coli has shown that its RNA-dependent ATPase activity is physically inseparable from its termination activity. The biochemical properties of pATPase have been studied using poly(C) as the activating RNA. This reaction is stimulated by Mg2+ ions and Mn2+ ions and is prevented by excess EDTA; it is not stimulated by Ca2+ ions. The reaction is not affected by a Zn2+ ion chelator and is inhibited by 1 mM Zn2+. With Mg2+ present, the activity is essentially constant from pH 7 to pH 9.7. pATPase is sensitive to p-hydroxymercuribenzoate and to N-ethylmaleimide. All four ribonucleoside triphosphates are hydrolyzed by p action. ATP has the lowest Km (0.009 mM), while CTP has the highest Vmax. In a mixture containing all four nucleoside triphosphates at a concentration of 0.4 mM, p shows no strong preference for any one of the substrates. The response of p ATPase to a variety of inhibitors of other ATPases and GTPases and of transcription has been studied. Of the compounds tested, aurintricarboxylic acid, an inhibitor of protein-nucleic acid interactions, was found to be a potent inhibitor of p ATPase, while rifampicin and heparin had no effect. pATPase showed partial sensitivity to thiostrepton, fusidic acid, Dio 9, and sodium azide.
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PMID:Characterization of the nucleoside triphosphate phosphohydrolase (ATPase) activity of RNA synthesi termination factor p. I. Enzymatic properties and effects of inhibitors. 13 81


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