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PubMed1977

The effect of atebrin on bacterial membrane adenosine triphosphatases in relation to the divalent cation used as substrate and/or activator.

The action of atebrin on purified adenosine triphosphatase (ATPase) from Micrococcus lysodeikticus was studied as well as on the membrane-bound and soluble ATPases from Escherichia coli and Bacillus megaterium. Atebrin inhibited the Ca(2+)-dependent activity of all these enzymes, and the inhibition was reversed by an excess of Ca(2+) ions. Kinetic studies carried out with the purified enzyme from M. lysodeikticus showed that the inhibition by atebrin was strongly cooperative, suggesting the complex nature of the process. On the other hand, atebrin stimulated the Mg(2+)ATPase activity of the M. lysodeikticus enzyme, displacing its adenosine 5'-triphosphate (ATP)/Mg(2+) optimum ratios, but inhibited the Mg(2+)-ATPase activity of E. coli provided that ATP was in excess over Mg(2+), i.e., that the ATP/Mg(2+) ratio was higher than its optimum. These results suggest that divalent cations influence the bacterial ATPases in different ways depending on the type of divalent ion and/or enzyme. The effect of atebrin on bacterial ATPases may reflect those differences, and its complex mechanism of action might be related to the existence of more than one site for divalent cations and/or distinct conformational states in these enzymes.

Adenosine Triphosphatases↗
PubMed1977

Molecular organization of subunits of electroplax (sodium plus potassium)--activated adenosine triphosphatase.

Antisera against each of the two major subunits of detergent-solubilized electroplax (sodium plus potassium)-activated adenosine triphosphatase from Electrophorus electricus were prepared. Antiserum against the small subunit (a glycoprotein, Mr = 58,000) partially inhibits [3H]ouabain binding to the enzyme, but does not interfere with the phosphorylation of enzyme. Conversely, antiserum against the large subunit (the catalytic subunit Mr = 96,000) partially inhibits phosphorylation of the enzyme, but does not interfere with the binding of [3H]ouabain to the enzyme. Since ouabain only interacts with enzyme from the outer surface of the membrane and phosphorylation of enzyme takes place on the inner surface of the membrane, the results suggest that the small subunits are exposed on the outer surface of the membrane, whereas the large subunits are oriented predominantely facing the cytoplasmic side.

Adenosine Triphosphatases↗
PubMed1977

The fine structural localization of adenosine triphosphatase activity on the taste bud in the fungiform papillae of the rat.

The localization of Mg++ activated adenosine triphosphatase (ATPase) activity in rat fungiform taste buds was demonstrated by electron microscopic histochemistry. Reaction product was found on the cell membrane of the taste cells, but not within their cytoplasm. Especially strong reaction occurred in the taste pore. Besides, enzymes were observed in axon-Schwann cell and axon-type I cell interspace, but not in the contacts of the nerve fiber and type II cell. The taste bud could well be distinguished from the surrounding epithelium by the existence of the reaction product. ATPase activity was absent at the synaptic portion where type III cells faced nerve fibers. No reaction product was seen along the basal lamina. In fungiform buds, the nerve fibers were frequently shown to make contact with each other, and these sites were devoid of deposits for ATPase.

Adenosine Triphosphatases↗
PubMed1975

Structural studies of sodium and potassium ion-activated adenosine triphosphatase. The relationship between molecular structure and the mechanism of active transport.

Sodium and potassium ion-activated adenosine triphosphatase is the enzyme responsible for the active transport of sodium and potassium across the plasma membrane. Strophanthidin, from the external surface of the membrane, and an antibody, from the cytoplasmic surface, bind simultaneously to the large polypeptide subunit of the enzyme. These results demonstrate that this polypeptide chain must span the plasma membrane, having different surfaces exposed on each side. When (Na+ + K+)-ATPase is incubated in the presence of cupric phenanthroline, a reagent which catalyzes the oxidation of cysteine residues to form intermolecular and intramolecular disulfide bonds, a covalent dimer of the larger chains is formed. Several characteristics of this dimerization reaction are consistent with the proposal that at least a noncovalent dimer of large chains exists in the native enzyme. These conclusions are discussed in the context of a specific description for the molecular mechanism of active transport.

Adenosine Triphosphatases↗
PubMed1976

[The activity and properties of adenosine triphosphatase in various swine organs (liver, cerebral and kidney cortex, small intestinal mucosa)].

Studies into the activity of adenosine triphosphatase (ATPase) in homogenates of liver, cerebral cortex, renal cortex, and mucosa of small intestine of swine have shown differentiated activity patterns, with peak activity developing in the liver. This has been related to a particularly high metabolism performance of the liver in fattening pigs. No difference was found to exist between magnesium activation of ATPase of swine tissue homogenates and that in tissue obtained from ruminants. ATPase which could be activated by sodium and potassium ions and inhibited by ouabain was detectable from cerebral and renal cortex. Sodium and potassium ATPases accounts from some 25 per cent of the total activity. ATPase that could be stimulated by calcium ions was recorded only from liver homogenate. The optimum pH values of ATPase were between 7.5 and 8 in the liver, 9 in mucosa of small intestine, and 9.5 in cerebral and renal cortex.

Adenosine Triphosphatases↗
PubMed1977

Inhibition by lead ion of Electrophorus electroplax (Na+ + K+)-adenosine triphosphatase and K+-p-nitrophenylphosphatase.

Inorganic lead ion in micromolar concentrations inhibits Electrophorus electroplax microsomal (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase) and K+-p-nitrophenylphosphatase (NPPase). Under the same conditions, the same concentrations of PbCl2 that inhibit ATPase activity also stimulate the phosphorylation of electroplax microsomes in the absence of added Na+. Enzyme activity is protected from inhibition by increasing concentrations of microsomes, ATP, and other metal ion chelators. The kinetics follow the pattern of a reversible noncompetitive inhibitor. No kinetic evidence is elicited for interactions of Pb2+ with Na+, K+, Mg2+, ATP, or p-nitrophenylphosphate. Na+- ATPase, in the absence of K+, and (Na+ + K+)-NPPase activity at low [K+] are also inhibited. ATP inhibition of NPPase is not reversed by Pb2+. The calculated concentrations of free [Pb2+] that produce 50% inhibition are similar for ATPase and NPPase activities. Pb2+ may act at a single independent binding site to produce both stimulation of the kinase and inhibition of the phosphatase activities.

4-Nitrophenylphosphatase↗
PubMed1978

Primary structures of cysteine-containing peptides from the calcium ion-transporting adenosine triphosphatase of rabbit sarcoplasmic reticulum.

A preliminary investigation of the primary structure of the Ca(2+-transporting ATPase (adenosine triphosphatase) protein of rabbit skeletal-muscle sarcoplasmic reticulum is reported. The preparation of derivatives of delipidated protein in a form suitable for sequence analysis is described. Tryptic peptides containing S-carboxymethylcysteine residues were isolated from the reduced carboxymethylated protein, and their sequences were partially determined. The results are consistent with mol.wt. about 105000 for the polypeptide, and the absence of extended repeated lengths of sequence. The distribution of tryptophan and cysteine residues between large, aggregated peptides and soluble tryptic peptides shows that these residues are concentrated in different regions of the primary structure. This observation agrees with other evidence that these residues are, on the whole, widely separated in the native protein. The details of the procedures used to isolate the peptides, and the evidence for the determination of their sequences, are given Supplementary Publication SUP 50085 (30 pages), which has been deposited at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem.J. (1978) 169, 5.

Adenosine Triphosphatases↗
PubMed1981

Fine structural localization of adenosine triphosphatase activities in the saccus vasculosus of the rainbow trout, Salmo gairdneri Richardson.

The following characteristics of the adenosine triphosphatases (ATPase) in the saccus vasculosus were studied in Salmo gairdneri Richardson: 1) distributional pattern, 2) cytochemical properties in relation to different substrates, inhibitors, pH and bivalent metal ions, and 3) ultrastructural localization. Ultracytochemical studies using modifications of the Washstein-Meisel technique showed that within the pH range 7.1-8.0 several Mg++ or Ca++-activated ATPase are localized on the intracellular surface of membranes and in the cytoplasm of ependymal coronet cells and tanycytes ("supporting cells", "Zwischenzellen", glial cells"). The high ATPase activity at the level of the specialized luminal plasma membranes of coronet cell globules and of tanycyte microvilli is discussed in relation to phenomena of active transport and a possible resulting transfer of low-molecular weight substances into and/or from the cerebrospinal fluid (CSF). The localization of ATPase on the specialized membranes of primary vesicles is considered in connection with available structural and enzyme-cytochemical data on a possible function of these cell organelles in storage and release of substances (including Ca++ ions?). The cytoplasmic ATPase activity in coronet cells is ascribed to microtubules and/or possible existing contractile proteins/filaments, presumably concerned with internal transport or motility processes. In tanycytes ATPase activity is believed to be associated with the characteristic microfilamentous system of still unknown function. The ATPase activity in the (9 + 0) ciliary apparatus of globules could not be interpreted in terms of motility. The present study provides further support to the proposed hypothesis of the transport function of the saccus vasculosus, and an extension of the concept in the sense that not only the principal coronet cells, but also the tanycytes of this circumventricular organ are involved in CSF-homeostasis.

Adenosine Triphosphatases↗
PubMed1976

Effect of triiodothyronine on the synthesis and degradation of renal cortical (Na+ + k+)-adenosine triphosphatase.

The present studies concern the roles of synthesis and degradation of the large subunit of (Na+ + k+)-adenosine triphosphatase (NaK-ATPase) in the response to triiodothyronin (T3). Single doses of either the diluent of T3 (50 mug/100 g body weight) were given to two pairs of surgically thyroidectomized rats. Twenty hours after injection, the rats received 3H- or 35S-labeled methionine administered as a constant injusion into the tail vein for 1 h. The kidneys were removed either 8 h or 20 h after infusion and the eight kidneys were divided into pairs, as follows. I, 3H (diluent)/35S (T3); II, 35S (diluent)/3H (T3); III, 3H (diluent)/35S (diluent); IV, 3H (T3)/35S (T3). Partially purified NaK-ATPase was prepared from the pooled homogenates and prepared from the pooled homogenates and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAG-electrophoresis). The large subunit of NaK-ATPase was identified by (Na+ + mg2+)-dependent and K+-sensitive incorpotation of 32P from [gamma-32P]ATP. This component had an estimated molecular weight of 92,000 and migrated as a single peptide in gels of varying total carylamide concentration, with respect to: (1) Coomassie blue staining, (b) (Na+ + Mg2+)-dependent, K+-sensitive incorporation of 32P from [gamma-32-P]ATP, and (c) T3-dependent enhanced incorporation of labeled methionine. T3 augmented incorporation of labeled methionine into the large subunit by 44% 8 h after infusion of the amino acid and by 61% 20 h after infusion. Incorporation of methionine into two adjacent polypeptides in the SDS gels was unaffected by thyroid status. The effect otical NaK-ATPase was assessed by a double label technique. Pairs of thyroidectomized rats were injected with either the diluent or 50 mug of T3/100 g body weight at 48-h after the first injection (diluent or T3, i.e. Day "zero"). Kidney cortices were processed on either Day 4 or Day 6; the partially purified NaK-ATPase fraction was prepared, labeled with [gamma-32P]ATP, and analyzed by SDS-PAG-electrophoresis. The degredation rate constants of the large subunit were similar; 0.145 and 0.124 day-1 for the hypothyroid and T3-treated groups, respectively. Thus, the T2-dependent increase in incorporation of labeled methionine into the large subunit appears to result from enhanced synthesis and this increase is sufficient to account for the entire increase in both the number of the activity of the NaK-ATPase units.

Adenosine Triphosphatases↗
PubMed1989

Activation of heart sarcoplasmic reticulum Ca++-stimulated adenosine triphosphatase by insulin.

Although insulin is known to elicit a positive inotropic effect in cardiac muscle preparations, very little is known concerning the mechanism of this action. In view of the crucial role played by the sarcoplasmic reticular (SR) calcium transport in cardiac contractile events, the effects of insulin on the pig heart SR were investigated. Insulin activated the SR Ca++-stimulated adenosine triphosphatase (ATPase) in a concentration-dependent manner (0.1 mU to 1 U/ml); maximal activation (125%) was seen at 0.1 to 1 U/ml of insulin. Kinetic studies revealed that the insulin-induced activation was due to an increase in the apparent Vmax of Ca++-stimulated ATPase without any alteration in the Km. Insulin was found to bind with SR membranes in a specific manner and this binding was rapid, saturable and displacable. The dose-related increase in the activation of Ca++-stimulated ATPase was related linearly (r = 0.98) to binding of insulin with SR membranes; 50% activation of Ca++-stimulated ATPase was found to occur at 13.5 fmol of insulin binding per mg of SR protein. When insulin was allowed to dissociate by a 100-fold dilution of the insulin-receptor complex, the activity of SR Ca++-stimulated ATPase also declined gradually. Furthermore, proteolytic digestion on the membrane with trypsin (3 micrograms/mg of protein) decreased both insulin binding as well as the increase in Ca++-stimulated ATPase activity by about 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1977

Effect of removal of calcium-activated adenosine triphosphatase from rat mast cells by treatment with sodium glycocholate.

Sodium glycocholate was shown to remove a Ca2+-activated adenosine triphosphatase from the external surface of the rat mast cell without causing lysis. Sensitized mast cells pretreated with sodium glycocholate showed a decrease in histamine-releasing capacity when triggered with antigen, Synacthen and ATP. Release induced by calcium ionophore A23187 was unaffected.

Adenosine Triphosphatases↗
PubMed1966

Properties of phosphate bound to cerebral microsomes during adenosine-triphosphatase activity.

1. Ox-brain microsomes were incubated with [gamma-(32)P]ATP under various conditions. After the reaction, which was stopped with trichloroacetic acid, a small amount of phosphate remained bound to the washed precipitate. 2. Properties of the bound phosphate were studied by treatment with buffers and solvents. 3. The Na(+)-dependent increment in bound phosphate, predominant at low ATP concentration and features of which suggest involvement in the concomitant adenosine-triphosphatase activity, was rapidly released in both circumstances. 4. In aqueous media the labile phosphate was released entirely as inorganic phosphate at faster rates with increasing alkalinity. 5. In acidified chloroform-alcohol mixtures the released phosphate appeared both as inorganic phosphate and different single (32)P-labelled organic phosphates, which were tentatively identified as the relevant mono-alkyl phosphates, presumably derived by acid-catalysed alcoholysis of a labelled microsomal component, or components. 6. The labile phosphate corresponded to the P exchangeable with non-radioactive ATP added during the enzyme reaction. 7. The possible molecular nature of the labile fraction of the bound phosphate is discussed.

Adenosine Triphosphatases↗
PubMed1979

Adenosine triphosphatase activities in brain, kidney and liver of mice treated with toxaphene.

The sensitivity of Na+-K+ and Mg++ Adenosine Triphosphatases (ATPases) in mouse tissues to toxaphene, a highly chlorinated camphene, was determined both in vivo and in vitro. The brain and kidney Na+-K+ ATPase activities were significantly inhibited in vitro by toxaphene. Interestingly, the inhibition was not significantly increased with an increase in the concentration of toxaphene. The oligomycin-sensitive (mitochondrial Mg++ ATPase activities in mouse brain, kidney and liver fractions were significantly inhibited by toxaphene in a concentration-dependent fashion. The oligomycin-insensitive Mg++ ATPase in all tissues examined was also inhibited but less sensitive to toxaphene than mitochondrial Mg++ ATPase. In contrast to in vitro response, the brain ATPases were not altered in mice fed toxaphene by oral intubation for three days. The renal and hepatic ATPase activities were significantly decreased in toxaphene treated mice with the oligomycin-insensitive Mg++ ATPase activity being only slightly altered.

Adenosine Triphosphatases↗
PubMed1973

The role of Na-K-activated adenosine triphosphatase in potassium adaptation. Stimulation of enzymatic activity by potassium loading.

The specific activity of sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) in homogenates of rat kidneys increases when the dietary intake of potassium is chronically increased. The effect is seen first and is most prominent in the outer medulla, but large loads of potassium elicit an increase in the cortex as well. Levels of Na-K-ATPase in brian, liver, and muscle, by contrast, are unaffected by potassium loading. Although the changes in enzyme activity in the kidney resemble those reportedly produced by aldosterone, they are not induced by experimental sodium deprivation, and they can be evoked by potassium loading in the absence of the adrenal glands. The results suggest that Na-K-ATPase of renal tubular cells, presumably in the distal tubules and collecting ducts, plays an important role in the phenomenon of potassium adaptation and in the process by which potassium is excreted into the urine.

Adaptation, Physiological↗
PubMed1987

Hepatic microsomal adenosine triphosphatase and mitochondrial function. Response to cold and warm ischemia.

We investigated the response of mitochondrial function and microsomal adenosine triphosphatase (ATPase) activity in rat liver tissue subjected to in vitro ischemia at either 0 degree C to 4 degrees C or 37 degrees C for 30 to 60 minutes. Mitochondrial coupling, expressed as respiratory control index, was preserved at up to 60 minutes' cold ischemia. However, respiratory control index was decreased significantly from control by 30 minutes of warm ischemia. Both microsomal magnesium-activated ATPase and sodium-potassium ATPase activity were significantly increased by 60 minutes of warm ischemia yet were unaltered by 60 minutes of ischemia at 0 degree C to 4 degrees C. Warm ischemia produces deleterious effects on energy-generating (mitochondria) and energy-utilizing (ATPase) activity. Hypothermia provides a significant prolongation of cellular viability in ischemic tissue in terms of bioenergetic status. In addition to organ procurement and transplantation, hypothermic cytoprotection may prove valuable in areas such as shock, ischemia, and other clinical conditions of compromised visceral perfusion.

Adenosine Triphosphatases↗
PubMed1978

Inhibition, by a protease inhibitor, of the solubilization of the F1-portion of the Mg2+-stimulated adenosine triphosphatase of Escherichia coli.

The effects of two protease inhibitors on the solubilization of the membrane-bound Mg2+-adenosine triphosphatase (Mg-ATPase) of Escherichia coli were investigated. p-Aminobenzamidine prevented the solubilization of the Mg-ATPase during treatment of membranes with low-ionic-strength buffers containing ethylenediaminetetraacetic acid. p-Aminobenzamidine did not prevent subsequent solubilization of the Mg-ATPase by treatment of the membranes with chloroform. This method of solubilization yielded a preparation of similar apparent molecular weight but with a 10-fold-increased specific activity as compared with the Mg-ATPase solubilized by washing with low-ionic-strength buffer. However, in contrast to the latter preparation, the chloroform-solubilized Mg-ATPase did not reconstitute ATP-dependent energization of stripped membranes, which were prepared by low-ionic-strength washing in the absence of p-aminobenzamidine. Another protease inhibitor, epsilon-amino-n-caproic acid, did not effect the solubilization of the Mg-ATPase, but did inhibit the loss of activity occurring during concentration, by ultrafiltration, of the Mg-ATPase solublized by the low-ionic-strength treatment.

Adenosine Triphosphatases↗
PubMed1995

Altered adenosine triphosphatase activities in pigs with naturally occurring hypertrophic cardiomyopathy.

The purpose of this study was to determine whether myocardial adenosine triphosphatase (ATPase) activities were reduced in pigs with naturally occurring hypertrophic cardiomyopathy (HCM). The selection of hearts for the HCM and the normal control groups depended on histological examination. Specific ATPase activity and 5'-nucleotidase activity were measured in left ventricular myocardium obtained from HCM (n = 7) and normal control (n = 7) animals. The histological features of HCM included marked disorientation of muscle cells, thickening of the intramural coronary arterial wall with a narrowed lumen, endocardial fibrosis and myocardial fibrosis. The HCM group showed significant increases in both heart weight (32%) and heart weight to body weight ratio (46%). The total ATPase activity in crude homogenates from the HCM group was significantly decreased by 16%. Azide-sensitive ATPase (mitochondrial ATPase) activity, ouabain-sensitive ATPase (Na+, K+-ATPase) activity, basal Mg(2+)-ATPase activity and Ca(2+)-ATPase activity were all significantly decreased by 18%, 30%, 20% and 50%, respectively. In contrast, no significant decrease was found in the mean values for 5'-nucleotidase activity. These results suggest that myocardial ATPase activities are suppressed in pigs with naturally occurring HCM.

5'-Nucleotidase↗
PubMed1978

Electron microscopic localization of Mg2+ -dependent adenosine triphosphatase activity in the amphibian pancreas (Salamandra salamandra L. and Rana esculenta L.).

The ultrastructural distribution of Mg2+ -dependent adenosine triphosphatase (ATPase) activity has been investigated in the salamander and frog pancreas by using glutaraldehyde fixations and a modified Wachstein-Meisel reaction medium. In both species the reaction product (lead phosphate) was found associated with the plasma membrane external side of all islet cell types (B-, A- and D-cells) and of acinar and ductular/centro-acinar cells. Except the apical pole of salamander acinar and centro-acinar cells, usually devoid of reaction, no preferential distribution of enzyme activity depending on endocrine or exocrine cell aspects could be observed. Other specific enzyme localizations included the mitochondria matrices, nucleoles, condensed nuclear chromatin, periaxolemmal spaces in nerve bundles and sometimes the cleft of neuro-glandular junctions. The occurrence of reaction deposits in connective tissue, in the cytoplasm of both islet and exocrine cells and in the nerve fiber axoplasm was considered as a possible diffusion artifact. The reaction intensity, but not its distribution, varied sensibly with the incubation period. 2-iodoacetamide and p-chlormercuribenzoic acid decreased the amount of reaction deposits at the level of all reactive sites and especially in mitochondria. The specificity of Mg2+ -ATPase demonstration in this paper is analysed taking into account several inherent shortcomings of the Wachstein-Meisel incubation medium and of the fixative. The different enzyme localizations, as well as their functional significances are discussed in relation with the findings of other authors.

Adenosine Triphosphatases↗