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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)

The ATPase of matrix vesicles is not stimulated by calcium ions, nor do the vesicles have any capacity to metabolize glucose. ADPase of high activity is also present; thus vesicles cannot be a component of the conventional ATP cycle, in which energy is stored by phosphorylating ADP and released by hydrolyzing the resultant ATP. These results do not support speculations that matrix vesicles might function by concentrating calcium via an energy-dependent ion transport system such as those found in the plasma membrane and the sarcoplasmic reticulum. Matrix vesicles' alkaline phosphatase can be solubilized by treatment with certain detergents: sodium dodecyl sulfate (12 mM and 16 mM), cetylpyridinium chloride (14mM), and deoxycholic acid (DOC, 14 MM). The first two detergents denature the enzyme during storage whereas DOC does not. DOC will also solubilize ATPase and inorganic pyrophosphatase. Yields of the three enzymes are 85-95%. Dialysis of a DOC digest of vesicles removes DOC and 43% of protein, and also causes much of the alkaline phosphatase to become particulate once again.
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PMID:Matrix vesicles of bovine fetal cartilage: metabolic potential and solubilization with detergents. 12 41

Alkaline inorganic pyrophosphatase and Mg-ATPase are localized within the mitoplast of maize seeding mitochondria. NaF inhibited the PPase activity, whereas oligomycin and dicyclohexylcarbodiimide inhibited the Mg-ATPase activity. The mitoplast preparation synthesized PPi from Pi under conditions excluding hydrolysis of endogenous ATP. PPi synthesis was inhibited by ADP, antimycin A, NaCN and 2,4- dinitrophenol but not by oligomycin. It is suggested that PPi synthesis in the maize seedling mitochondria proceeds at the expense of the energy of electron transport chain and is independent of the ATP synthesis.
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PMID:Submitochondrial localization and function of alkaline inorganic pyrophosphatase in maize seedlings. 15 79

The effects of the alkaline phosphatase inhibitors levamisole and R 8231 on p-nitro-phenylphosphatase, inorganic pyrophosphatase and adenosine triphosphatase (ATPase) activities in dentingenically active odontoblasts were studied. The p-nitrophenylphosphatase and inorganic pyrophosphatase activities were inhibited, while 40% of the ATP-splitting enzyme activity remained under the assay condition used. This finding, togeather with earlier studies, indicates that at least two different phosphatase are active at alkaline pH in hard tissue-forming cells; on nonspecific alkaline phosphatase and one specific ATPase. The ATPase activity is uninfluenced by ouabain and ruthenium red and is activated by Ca-2+ ions.
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PMID:Inhibition studies of alkaline phosphatase in hard tissue-forming cells. 16 33

The synthesis of inorganic pyrophosphate by the mitochondria of Endomyces magnusii was found to be coupled with respiration. The mitochondria of E. magnusii can utilize the energy of the phosphoanhydride bond of inorganic pyrophosphate for the synthesis of ATP. The study with inhibitors suggests the participation of inorganic pyrophosphatase and ATPase in this process.
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PMID:[Inorganic pyrophosphate synthesis by the mitochondria of the yeast-like fungus Endomyces magnusii coupled with the work of the respiratory chain]. 17 78

Sulfate-reducing bacteria, Desulfovibrio vulgaris, strain Miyazaki, were grown on either sulfate, sulfite, or thiosulfate as the terminal electron acceptor. Better growth was observed on sulfite and less growth on thiosulfate than on sulfate. Enzyme levels of adenylylsulfate (APS) reductase [EC 1.8.99.2], reductant-activated inorganic pyrophosphatase [EC 3.6.1.1], sulfite reductase [EC 1.8.99.1] (desulfoviridin), hydrogenase [EC 1.12.2.1], and Mg2+-activated ATPase [EC 3.6.1.3] were compared in crude extracts of these cells at various stages of growth. 1) The specific activity of APS reductase in sulfite-grown cells was only one-fourth that in sulfate-grown cells throughout growth. Thiosulfate-grown cells had an activity intermediate between those of sulfate- and sulfite-grown cells. 2) Cells grown on sulfite had lower specific activity of reductant-activated inorganic pyrophosphatase than cells grown on sulfate or thiosulfate. 3) The specific activity of sulfite reductase (desulfoviridin) was highest in sulfite-grown cells. The sulfite medium gave the enzyme in high yield as well as with high specific activity. 4) The specific activities of hydrogenase and Mg2+-ATPase were not significantly altered by electron acceptors in the growth medium.
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PMID:Biochemical studies on sulfate-reducing bacteria. XIV. Enzyme levels of adenylylsulfate reductase, inorganic pyrophosphatase, sulfite reductase, hydrogenase, and adenosine triphosphatase in cells grown on sulfate, sulfite, and thiosulfate. 17 50

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.
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PMID:Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved. 18 60

An isotopic shift of the (31)P nuclear magnetic resonance due to (18)O bonded to phosphorus of 0.0206 ppm has been observed in inorganic orthophosphate and adenine nucleotides. Thus, the separation between the resonances of (31)P(18)O(4) and (31)P(16)O(4) at 145.7 MHz is 12 Hz and, in a randomized sample containing approximately 50% (18)O, all five (16)O-(18)O species are resolved and separated from each other by 3 Hz. Not only does this yield the (18)O/(16)O ratio of the phosphate but, more important, the (18)O-labeled phosphate in effect can serve as a double label in following phosphate reactions, for oxygen in all cases and for phosphorus, provided the oxygen does not exchange with solvent water. Thus, it becomes possible to follow labeled phosphorus or labeled oxygen continuously as reactions proceed. Rate studies involving (i) phosphorus and (ii) oxygen are illustrated by continuous monitoring of the exchange reactions between (i) the beta phosphate of ADP and inorganic phosphate catalyzed by polynucleotide phosphorylase and (ii) inorganic orthophosphate and water catalyzed by yeast inorganic pyrophosphatase. In the ADP-P(i) exchange, the P(i) ((18)O(4)) yielded an alpha P((16)O(3) (18)O) and a beta P((18)O(4)), proving that bond cleavage occurs between the alpha P and the alpha-beta bridge oxygen. Among the many additional potential uses of this labeling technique and its spectroscopic observation are: (i) different labeling of each phosphate group of ATP, (ii) to follow rate of transfer of (18)O from a nonphosphate compound such as a carboxylic acid to a phosphate compound, and (iii) to follow the rate of scrambling (for example, of the beta-gamma bridge oxygen of ATP to nonbridge beta P positions) and simultaneously the rate of exchange of the gamma P nonbridge oxygens with solvent water in various ATPase reactions.
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PMID:Isotopic (18O) shift in 31P nuclear magnetic resonance applied to a study of enzyme-catalyzed phosphate--phosphate exchange and phosphate (oxygen)--water exchange reactions. 20 29

1. The 25 000-30 000 X g fraction from sugar beet leaf or roots contains, together with (Na+ plus K+)-activated ATPase, also K+-stimulated inorganic pyrophosphatase. 2. This inorganic pyrophosphatase is also stimulated by Rb+ and to a lesser degree by Li+ and Na+. 3. Na+ is at the same time an inhibitor to the K+-stimulation of the inorganic pyrophosphatase. 4. No signs of synergism for (Na+ plus K+) were found. 5. Optimum pH was at about 8.5.
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PMID:Membrane-bound potassium and magnesium ion-stimulated inorganic pyrophosphatase from roots and cotyledons of sugar beet (Beta vulgaris L). 24 Apr 14

ATP sulphurylase (ATP:sulphate adenylyltransferase, EC 2.7.7.4) as been purified about 2500-fold from rat liver. It was free of ATPase, inorganic pyrophosphatase, adenosine phosphosulphate kinase and ADP sulphurylase activities. The enzyme was homogeneous to chromatography on Sepharose 4B and to density-gradient sedimentation; it was not homogeneous to acrylamide gel electrophoresis nor to sedimentation in the ultracentrifuge. Possible reasons for this heterogeneity are considered. The molecular weight of the enzyme is 410 000 as measured by chromatography on Sepharose 4B. The v is 0.80, suggesting that ATP sulphurylase is a lipoprotein. The enzyme activity is associated with a pigment having a lambdamax of 410 nm. Studies of the forward, reverse and ATP-PPi exchange reactions catalysed by ATP sulphurylase have shown that these are sequential bi-bi reactions, with ATP being the first substrate bound and adenosine phosphosulphate the last product released. The results are incompatible with previous suggestions that the ATP sulphurylase of rat liver catalysed a bi-bi ping-pong reaction.
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PMID:Purification and properties of the ATP sulphurylase of rat liver. 71 62

We have studied a mitochondrial inorganic pyrophosphatase (PPase) in the yeast Saccharomyces cerevisiae. The uncoupler FCCP (carbonyl cyanide p-trifluoromethoxyphenylhydrazone) and the ionophores valinomycin and nigericin stimulate the PPase activity of repeatedly washed yeast mitochondria 2-3-fold. We have previously cloned a yeast gene, PPA2, encoding the catalytic subunit of a mitochondrial PPase. Uncouplers stimulate the PPase activity several-fold in mitochondria from both cells that overexpress PPA2 from a high copy number plasmid and cells with normal expression. These results indicate that the PPA2 polypeptide functions as an energy linked and membrane associated PPase. The stimulation of mitochondrial PPase activity by FCCP, but not by valinomycin and nigericin, was greatly enhanced by the presence of DTT. The antibiotics Dio-9, equisetin and the F0F1-ATPase inhibitor oligomycin also increase mitochondrial PPase activity several fold. This stimulation is much higher, whereas basal PPase activity is lower, in isotonic than in hypotonic solution, which indicates that intact membranes are a prerequisite for maximal effects.
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PMID:Characterization of a mitochondrial inorganic pyrophosphatase in Saccharomyces cerevisiae. 130 54


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