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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)

Adenosine triphosphatase (ATPase) and simple esterase (SE) have been mapped at various levels of the cerebral hemispheres of the lizard, Uromastix. Some areas were intensely positive for one or both enzymes while others were totally negative for both. Variation in enzymatic activity has been observed at different levels in the same nucleus. The functional significance of the findings is discussed.
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PMID:Histochemical mapping of ATPase and simple esterase in the cerebral hemisphere of the Indian lizard, Uromastix hardwickii. 12 18

The source of metabolic energy for the accumulation of methionine in cells of Escherichia coli was shown to differ from that for proline uptake. In contrast to proline uptake, methionine accumulation was sensitive to arsenate, and relatively resistant to azide or dinitrophenol. Adenosine triphosphatase mutant strains also differentiated between the two systems, consistent with the conclusion that, although proline uptake is driven directly by the energized membrane state, methionine uptake is not. Methionine transport is similar to that of other osmotic shock-sensitive systems in its direct utilization of adenosine 5'-triphosphate or a related compound as energy source.
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PMID:Energy coupling for methionine transport in Escherichia coli. 12 47

Basal and trypsin-stimulated adenosine triphosphatase activities of Escherichia coli K 12 have been characterized at pH 7.5 in the membrane-bound state and in a soluble form of the enzyme. The saturation curve for Mg2+/ATP = 1/2 was hyperbolic with the membrane-bound enzyme and sigmoidal with the soluble enzyme. Trypsin did not modify the shape of the curves. The kinetic parameters were for the membrane-bound ATPase: apparent Km = 2.5 mM, Vmax (minus trypsin) = 1.6 mumol-min-1-mg protein-1, Vmax (plus trypsin) = 2.44 mumol-min-1-mg protein-1; for the soluble ATPase: [S0.5] = 1.2 mM, Vmax (-trypsin) = 4 mumol-min-1-mg protein-1; Vmax (+ trypsin) = 6.6 mumol-min-1-mg protein-1. Hill plot analysis showed a single slope for the membrane-bound ATPase (n = 0.92) but two slopes were obtained for the soluble enzyme (n = 0.98 and 1.87). It may suggest the existence of an initial positive cooperativity at low substrate concentrations followed by a lack of cooperativity at high ATP concentrations. Excess of free ATP and Mg2+ inhibited the ATPase but excess of Mg/ATP (1/2) did not. Saturation for ATP at constant Mg2+ concentration (4 mM) showed two sites (groups) with different Kms: at low ATP the values were 0.38 and 1.4 mM for the membrane-bound and soluble enzyme; at high ATP concentrations they were 17 and 20 mM, respectively. Mg2+ saturation at constant ATP (8 mM) revealed michealian kinetics for the membrane-bound ATPase and sigmoid one for the protein in soluble state. When the ATPase was assayed in presence of trypsin we obtained higher Km values for Mg2+. These results might suggest that trypsin stimulates E. coli ATPase by acting on some site(s) involved in Mg2+ binding. Adenosine diphosphate and inorganic phosphate (Pi) act as competitive inhibitors of Escherichia coli ATPase. The Ki values for Pi were 1.6 +/- 0.1 mM for the membrane-bound ATPase and 1.3 +/- 0.1 mM for the enzyme in soluble form, the Ki values for ADP being 1.7 mM and 0.75 mM for the membrane-bound and soluble ATPase, respectively. Hill plots of the activity of the soluble enzyme in presence of ADP showed that ADP decreased the interaction coefficient at ATP concentrations below its Km value. Trypsin did not modify the mechanism of inhibition or the inhibition constants. Dicyclohexylcarbodiimide (0.4 mM) inhibited the membrane-bound enzyme by 60-70% but concentrations 100 times higher did not affect the residual activity nor the soluble ATPase. This inhibition was independent of trypsin. Sodium azide (20 muM) inhibited both states of E. coli ATPase by 50%. Concentrations 25-fold higher were required for complete inhibition. Ouabain, atebrin and oligomycin did not affect the bacterial ATPase.
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PMID:Membrane bound and soluble adenosine triphosphatase of Escherichia coli K 12. Kinetic properties of the basal and trypsin-stimulated activities. 12 30

Adenosine triphosphatase activity not dependent on sodium or potassium but inhibited by thiocyanate is present in broken-cell homogenates of eel gill and rat kidney. This enzymatic property is predominantly associated with mitochondria, although thiocyanate-inhibited ATPase can also be detected in microsomes with little or no mitochondrial contamination as measured by the activity of the mitochondrial marker enzyme succinic dehydrogenase. When eels are transferred from fresh to salf water, thus increasing active outward transport of chloride across the gill, the thiocyanate-inhibited ATPase of gill microsomes does not change, though the activities of succinic dehydrogenase and Na-K-ATPase in gill homogenates are augmented. The thiocyanate-inhibited ATPase of homogenates of outer renal medulla does not differ from that of renal cortex, in contrast to Na-k-atpase which is higher in renal medulla than in cortex. The data do not support a role for thiocyanate-inhibited ATPase in active chloride transport by epithelial tissues.
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PMID:Thiocyanate inhibition of ATPase and its relationship to anion transport. 12 12

The choroid plexuses are characterized by the absence of alcaline phosphatase activity as well as the absence of any vascular barrier for proteins as revealed by fluorescein tracer observation. This correlation is interpreted as supporting the hypothesis of enzymatic control, via alcaline phosphatase, of the blood-brain barrier. Adenosine mono and triphosphatase activity, on the contrary, is identical in choroid plexus vessels and in vessels where the blood-brain barrier phenomena may be demonstrated.
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PMID:[Histochemical correlations of vascular permeability and enzyme activity in the choroid plexus in man]. 12 95

Measurement of certain membrane-bound enzymic activities was used to study the orientation of the outer membrane of the double-membraned forespore of Bacillus megaterium KM. 2. Adenosine triphosphatase, NADH dehydrogenase and L-malate intact protoplasts, but were readily detected in intact stage II or IV forespores, consistent with reversed polarity of the outer forespore membrane relative to the mother-cell plasma membrane. 3. Measurement of NADH oxidase activity revealed that intact stage III forespores had the same high affinity for NADH as protoplast membrane preparations and protoplast lystates, consistent with ready access of NADH to oxidation sites on the outer forespores membrane. 4. Forespores and protoplasts showed osmometric behaviour in solutions of non-permanent solutes consistent with the presence of an intact permeability barrier in these structures.
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PMID:Biochemical evidence for the reversed polarity of the outer membrane of the bacterial forespore. 13 69

The characteristics of the glycolytic pathway and the plasma membrane of Lactobacillus and Bifidobacterium were studied. The enzyme system of glycolysis (hexokinase, glucokinase and pyruvate kinase) which is the main source of energy in the anaerobic condition was localized in the cell soluble fraction (cytoplasma) of all species examined. Neither electron transfer chain components nor oxidase activities were found in anaerobically cultured Lactobacillus and Bifidobacterium. Adenosine triphosphatase (ATPase) activities were mainly localized in the plasma membrane, suggesting that membrane ATPase is playing a key role in membrane transport and ATP synthesis of anaerobic bacilla. SDS-polyacrylamide gel electrophoresis of membranes showed remarkable differences between the polypeptides patterns of B. adolescentis and B. bifidum. Such peculiarities in polypeptide patterns among the same genus may be useful in the identification of species.
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PMID:Characterization of the glycolysis pathway and the plasma membrane of Lactobacillus and Bifidobacterium strains. 13 31

Adenosine triphosphatase (ATPase) activity was localized at an ultrastructural level in the resting mammary glands of female BALB/c mice. A Mg++ dependent ATPase was localized in the plasma membranes of both the epithelial and myoepithelial cells of the mammary tubules. A second type of ATPase activity that was not Mg++-dependent but that was Na+ and K+ dependent was localized primarily in the plasma membranes of the myoepithelial cells. Preincubation with either ouabain or N-ethylmaleimide decreased the quantity of reaction product, indicating that both types of ATPase activity were sensitive to these inhibitors. Control media, containing adenosine triphosphate and Pb(NO3)2 without cations, demonstrated that the amount of nonezymatic hydrolysis was negligible. These differences in the cationic requirements for plasma membrane ATPase activity can be used to distinguish histochemically the epithelial from myoepithelial cells in mammary tissue.
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PMID:Ultrastructural localizations of adenosine triphosphatase activity in resting mammary gland. 13 6

Ultrastructural distribution of adenosine triphosphatase and thiamine pyrophosphatase in synapses of rat's cerebral cortex was studied. Adenosine triphosphatase activity in some synaptic vesicles and mitochondria, on pre- and postsynaptic membranes, as well as in the postsynaptic thickening was established. The reaction specificity was proved by means of some controls: various concentrations of ouabain, NaF, NiCl2, cysteine, substrate free medium and non-specific substrates - cocarboxylase and beta-glycerophosphate. At the thiamine pyrophatase reaction, the enzyme positive product was found on the membrane of some clear synaptic vesicles, on the singl sacs of smooth endoplasmic reticulum in the axon terminal, and bouton cell membrane. Substrate free medium, addition of cystein and substitution of orininal substrate with adenosine triphosphate and beta-glycerophosphate as controls were used. The fine structure localization of both enzymes in synaptic structures suggests their important role in the synaptic function.
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PMID:Cytochemical localization of adenosine triphosphatase and thiamine pyrophosphatase in the synapases of rat's cerebral cortex. 14 1

Three parts were distinguished by electron microscopy and by enzyme histochemistry at the boundary zone between the white and red pulp of the human spleen. The first was the inner layer of the perifollicular region, composed of medium-sized lymphocytes with abundant free ribosomes in their cytoplasm. A small number of reticulum cells intervened among these lymphocytes. This inner layer was considered to correspond to the "Follikelaussenzone" (Strasser). The second was the outer layer of the perifollicular region, composed of a meshwork of reticulum cells with reticular fibers, and sheathed and non-sheathed arteries. Small and medium-sized lymphocytes, granulocytes, erythrocytes, platelets, and a small number of plasma cells were observed in the mesh spaces. This outer layer was considered to correspond to the "marginal zone" (Snook). At the outermost part of this layer, the venous sinus appeared. There was no distinct border between this layer and the red pulp. The third was the neighboring region of the periarterial lymphoid sheath, showeing similar structure and cellular components to the outer layer of the perifollicular region. It was characteristic feature for the lymphocytes and some of the reticulum cells of this region to have a strong activity for alkaline phosphatase reaction, while the lymphocytes of the outer layer showed only a weak activity. Adenosine triphosphatase and 5'-nucleotidase activities were demonstrated on the lymphocytes of these three parts of the boundary zone as well as the lymph follicle. Different activities for these enzyme reactions may indicate the functional properties of the B-cell system.
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PMID:An electron microscopic and enzyme histochemical study of the boundary zone between the white and red pulp of the human spleen. 14 41


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