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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Changes in the concentrations of ATP, ADP, AMP, IMP, creatine and phosphorylcreatine (PC) have been measured in frog sartorius muscles after different periods of isometric stimulation at 20 degrees C. The heat production was measured in parallel experiments with a thermopile of the Hill-Downing type.2. Muscles were either in O(2) and unpoisoned or in N(2) and poisoned with iodoacetic acid to prevent aerobic and glycolytic recovery processes.3. Poisoning did not appear to alter the heat production of these muscles and had little effect on the tension for up to 8 sec tetanus.4. The break-down of high-energy phosphates ( approximately P) during contraction was faster in the poisoned muscles. Normal muscles were thus able to resynthesize high energy phosphates during the contraction. The resynthesis began at its maximum rate; part of it was probably due to glycolytic activity.5. During the first 2 sec of contraction (poisoned muscles), the only net reaction was an hydrolysis of PC, with an apparent enthalpy change of -8.3 kcal/mole. During longer contractions, the PC hydrolysis was accompanied by a net ATP hydrolysis and appearance of AMP and IMP.6. For the first 2 sec of contraction in the poisoned muscles, the observed heat agreed with that expected from the observed chemical changes multiplied by their molar enthalpy changes. After 2 sec, the observed heat was greater than that expected. At 12 sec this excess was about 74 mcal/g. Possible explanations for this discrepancy are discussed.
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PMID:Energy balance in frog sartorius muscle during an isometric tetanus at 20 degrees C. 475 78

1. The general characteristics and Na and K movements of L cells (derived from mouse epithelium) have been measured. Both cells grown in suspension (LS cells) and as a monolayer (L cells) were used.2. The volume of L cells was 1.2 x 10(-9) cm(3) and of LS cells 3.5 x 10(-9) cm(3); of this 82% was water.3. Electron micrographs showed the presence of numerous protrusions (filopodia) from both forms of the cell. These had the effect of increasing the surface area of the cell by 2-4 times over smooth cells of the same volume. On changing from the flattened to the spherical shape during trypsinization, the filopodia altered to maintain a constant V/A ratio.4. These cells contain K, about 170 m-mole/l. intracellular water and Na, 9 m-mole/l. intracellular water (L cells only) at 20 degrees C. The K fluxes are 1.9 p-mole/cm(2) sec for LS cells and 0.8 p-mole/cm(2) sec for L cells and the Na fluxes are 1.8 p-mole/cm(2) sec for L cells (expressed as per total cell surface (including filopodia)). If expressed as p-mole/cell per sec then L and LS cells have the same K flux.5. 10(-4)M ouabain reduces the K influx to half, indicating an insensitivity to the glycosides common to the species. In the prolonged presence of ouabain the cells come into a new steady state with a [K](1), of 140 and a [Na](1) of 20-30 m-mole/l. intracellular water, but a constant [Na + K](1).6. Both DNP (10(-3)M) and IAA (10(-4)M) are required for maximum inhibition of K uptake, as both aerobic and anaerobic metabolic pathways may be used to drive the pump.7. K removal decreases the Na efflux, and Na removal (eventually) decreases the K influx providing evidence for Na/K coupling.8. The cells contain 7.5 m-mole/litre intracellular water of ATP, a level some 15 times that of ADP.9. The Na pump in these cells is very similar to that found in other tissues in that (a) it requires K to work, (b) it is blocked by ouabain and metabolic inhibitors and (c) it transports three molecules of Na for each two molecules of K.
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PMID:Effect of ouabain and metabolic inhibitors on the Na and K movements and nucleotide contents of L cells. 510 32

Certain aspects of adenosine triphosphate (ATP) metabolism in the strict anaerobe Methanobacterium strain M.o.H. have been investigated. Results of growth yield studies suggest that ATP conservation is very inefficient (0.06 mole of ATP per mole of hydrogen) under the conditions used to grow the bacterium in a fermentor. Experiments designed to demonstrate net ATP formation in cell-free extracts were negative. In whole-cell studies, substances which decreased ATP pool levels and increased adenosine monophosphate (AMP) pool levels were air, chloroform, 2,4-dinitrophenol, carbonylcyanide-m-chlorophenylhydrazone, and pentachlorophenol. The results suggest that the latter compounds act either as inhibitors of electron transport or as uncouplers of an energy-linked process. All the above compounds also inhibit methane formation in cell-free extracts, an ATP-requiring process. Methods are described for estimation of ATP, adenosine diphosphate (ADP), and AMP in whole cells, with a sensitivity in the range of 10 to 200 pmoles. An apparatus for quick sampling from an anaerobic suspension of whole cells also is described.
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PMID:Adenosine triphosphate pools in Methanobacterium. 543 31

Human blood platelets were subjected to osmotic shock, brief sonication, pressure homogenization, or treatment with adenosine diphosphate (ADP). These procedures demonstrated an abundance of cytoplasmic microfibrils. The fibrils resembled those found on electron microscopy of partially purified thrombosthenin, the actomyosin-like protein isolated from platelets, and they also appeared to resemble the myofilaments of smooth muscle. Similar fibrils were not found in leukocytes studied under identical conditions. Treatment with colchicine (2 x 10(-5) mole/liter) resulted in the disappearance of microtubules but did not affect the morphology of the microfibrils or interfere with platelet-dependent clot retraction. Thus, microfibrils rather than microtubules may represent the morphologic counterpart of the contractile protein. Brief osmotic shock at low temperature or treatment with 10(-4) M ADP caused the marginal band of microtubules to be replaced by a bundle of intertwining microfibrils. The apparent inter-conversion of microtubules and microfibrils under a variety of conditions led to the hypothesis that fibrils and tubules consist of similar subunits whose degree of polymerization might be dependent on local cytoplasmic forces. Furthermore, on the basis of these observations, it is postulated that the contractile properties of the cells may be vested in the microfibrils, whereas the tubules may serve to maintain the highly asymmetric shape characteristic of circulating and irreversibly aggregated platelets.
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PMID:Microfibrils of blood platelets: their relationship TO MICROTUBULES AND THE CONTRACTILE PROTEIN. 576 19

1. Adenylate kinase (EC 2.7.4.3) has been shown to be present in human plasma obtained by conventional means and the adenylate-kinase activities of plasma and of lysed and intact human platelets and erythrocytes have been measured at 37 degrees by sensitive spectrophotometric methods. 2. The activities found in plasma ranged from 2.7 to 22.9mumoles of ADP formed/min./l. and in lysed platelets and lysed erythrocytes mean values of 0.79 and 12.0mumoles of ADP formed/min./10(9) cells respectively were found. Intact platelets and erythrocytes showed little or no activity. 3. The apparent K(m) of plasma adenylate kinase for ADP was found to be 1.4-1.6mm. 4. The adenylate-kinase activity of plasma was correlated with the free haemoglobin present and the larger part of the activity could be accounted for by haemolysis occurring either during the withdrawal of the blood or in vivo. 5. Aggregation of platelets by ADP, collagen fibres or thrombin released up to 16% of the platelet adenylate kinase into the suspending medium. 6. Measurement of the rate of breakdown of 1.6mum-ADP in plasma gave values of about 0.1mmu-mole/min./ml. This was not increased by addition of sufficient erythrocyte lysate to increase the activity of plasma adenylate kinase five to ten times. 7. It was concluded that the activity of adenylate kinase found in plasma, even after aggregation of the platelets, is insufficient to account for the rate of breakdown of low concentrations of ADP usually observed, and that another enzyme is responsible for this process.
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PMID:The adenylate kinase of human plasma, erythrocytes and platelets in relation to the degradation of adenosine diphosphate in plasma. 604 99

The effects of methylmercuric chloride, mercuric chloride, and phenylmercuric acetate (10(-6) - 10(-3) mole/liter) on thrombin-induced release of adenine nucleotides from washed pig platelets were investigated. The inhibitory effects of mercurials were always reached when the higher thrombin concentration (0.74 units NIH/ml) was used. Incubation of washed pig platelets with methylmercuric chloride caused a decrease of intracellular level of platelet ATP and statistically significant changes in ATP/ADP ratio.
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PMID:Effects of mercurial compounds on adenine nucleotides of washed pig platelets. 621 73

In order to study the mechanism for activation of ATP hydrolysis by Mg2+, the stoichiometry of the high affinity calcium-binding sites with respect to each form of reaction intermediate of sarcoplasmic reticulum ATPase was determined at 0 degrees C and pH 7.0 in the presence and absence of added Mg2+ using the purified ATPase preparation. High affinity calcium binding to the enzyme-ATP complex and to ADP-sensitive (E1P) and ADP-insensitive (E2P) phosphoenzymes occurred with stoichiometric ratios of 2, 2, and 0, and 3, 3, and 1 in the presence and absence of added Mg2+, respectively. The results were interpreted to indicate that in addition to 2 mol of calcium bound to the transport sites of the ATPase, 1 mol of divalent cation, which is derived from the metal component of the substrate, the metal-ATP complex, remains bound to each mole of the enzyme at least until E2P is hydrolyzed. As activation of phosphoenzyme hydrolysis by Mg2+ was blocked by the low concentrations of Ca2+ used in the calcium binding experiments, it was concluded that it is the magnesium derived from MgATP that is responsible for rapid hydrolysis of the phosphoenzyme intermediate.
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PMID:Effect of divalent cation bound to the ATPase of sarcoplasmic reticulum. Activation of phosphoenzyme hydrolysis by Mg2+. 622 21

The nucleotide binding capacity and affinity of the isolated beta subunit from Escherichia coli F1-ATPase have been studied with radiolabeled ADP and ATP by an equilibrium dialysis technique. Each mole of beta subunit in the presence of EDTA bound 1 mol of ADP or ATP with Kd values of 25 microM and 50-100 microM, respectively. At a saturating concentration, aurovertin enhanced the affinity of ADP or ATP for the isolated beta subunit by 3-6-fold. The Kd values for the binding of ADP or ATP were also assessed through the enhancing effect of ADP on [14C]aurovertin binding (Issartel, J.-P., Klein, G., Satre, M., & Vignais, P.V. (1983) Biochemistry 22, 3485-3492); the Kd values determined by this approach were several times lower than in the absence of aurovertin, in agreement with results obtained by direct titration with radiolabeled ADP or ATP.
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PMID:Evidence for a nucleotide binding site on the isolated beta subunit from Escherichia coli F1-ATPase. Interaction between nucleotide and aurovertin D binding sites. 624 80

We have investigated the suitability of 5'-p-fluorosulfonylbenzoyladenosine (FSBA) as an ATP site affinity probe for the canine kidney Na+, K+-ATPase. The purified enzyme is slowly inactivated by this compound in suitable buffers, losing about half of its activity over a two-hour period. The rate of inactivation is more rapid in 0.1 M KCl than in 0.1 M NaCl. Low concentrations of ATP protect the enzyme against inactivation, with half-maximal effects at 4 microM ATP in 0.1 M NaCl and 350 microM ATP in 0.1 M KCl. ADP also protects against FSBA inhibition, but AMP is ineffective when present at 100 microM levels. This pattern is consistent with the previously described nucleotide specificity of the Na+, K+-ATPase. Addition of protective amounts of ATP after inactivation has occurred does not restore enzyme activity, indicating that inhibition is irreversible. Measurement of the concentration-dependence of FSBA inactivation suggests an apparent Kd for binding of this compound well above 1 mM, the solubility limit of the analog. This finding is reinforced by the failure of 1 mM FSBA to compete effectively with ATP for the high-affinity ATP site of the enzyme. Nevertheless, attachment of the analog to this site is indicated by its ability to prevent [3H]-ADP binding in proportion to the number of sites it has inactivated. Studies with [3H]-FSBA show that about 1 mole of the analog attaches specifically to the alpha subunit per mole of enzyme inactivated. A similar amount of nonspecific labeling also occurs with negligible effect on enzyme activity. These findings suggest that FSBA may be useful in probing the topography of the high-affinity ATP binding site of the Na+, K+-ATPase and related enzymes.
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PMID:5'-p-fluorosulfonylbenzoyladenosine as an ATP site affinity probe for Na+, K+-ATPase. 626 29

The maximal content of mitochondrial isoenzyme of creatine kinase (CK) in rat heart mitochondria does not exceed 12.5 moles per mole of ATP-ADP translocase. This value was obtained by titration of mitochondrial CK activity in aged mitochondria by 5,5'-dithiobis-(2-nitrobenzoate) (DTNB) and 2,4-dinitrofluorobenzene (DNFB) and by a more complex and accurate method. The essential thiol groups of membrane-bound mitochondrial CK (and its enzymic activity) can be specifically protected by phosphocreatine (12 mM) + ADP (1-5 mM) against inactivation by DTNB. Mitochondria with protected SH-groups of CK and with groups inactivated by DTNB were repeatedly incubated with DTNB under identical conditions and the number of additionally reacted sulfhydryl groups and the changes in CK activity were measured. The differences in the number of additionally reacted SH-groups correlated with the changes in the CK activity, which made it possible to calculate the molar ratios of mitochondrial CK to cytochrome c oxidase and ATP-ADP translocase (2.16 +/- (0.4): 1:2, respectively).
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PMID:[Determination of molar content of creatine kinase in heart mitochondria by SH-reagents]. 627 Dec 62


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