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)

Acid-base status influences many aspects of insect biology, including insect distributions in aquatic systems, insect-plant and insect-pathogen interactions, membrane transport phenomena, and the mode of action of pesticides. Acid-base status in the hemolymph and gut lumen of insects is generally well regulated but varies somewhat within individuals owing to effects of temperature, activity, discontinuous ventilation, and diet. The pH of the midgut lumen varies with the phylogeny and feeding ecology. Insect fluids have buffer values similar to those of vertebrates. The respiratory system participates in acid-base homeostasis primarily by regulating the internal carbon dioxide (partial) pressure via changes in spiracular opening and convective ventilation. The epithelia of the renal system and gut participate in hemolymph acid-base regulation by varying acid-base transport in response to organismal acid-base status. Evidence to date suggests that the dominant mechanisms for control of renal acid-base excretion involve hormonal regulation of H+-V-ATPase activity.
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PMID:Insect acid-base physiology. 1111 69

In the present study, we have investigated whether the lipopolysaccharide (LPS) endotoxin from Escherichia coli is able to alter the jejunal transport of L-leucine when the tissue is exposed to endotoxin. The results have shown that the LPS at 3 x 10(-5) microg/ml decreases the uptake of L-leucine into the enterocyte, as well as the mucosal to serosal flux of L-leucine. The secretagogue effect of LPS on the gut did not affect the inhibitory effect of LPS on the intestinal absorption of the amino acid. The endotoxin did not modify amino acid diffusion across the intestinal epithelium. However, from the mediated transport, only the Na+-dependent transport system was affected by LPS with a diminution of the transporter affinity (the apparent Km was increased). In addition, we found a reduction of the Na+, K+-ATPase activity, which could explain the L-leucine Na+-dependent transport inhibition.
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PMID:Effect of lipopolysaccharide on small intestinal L-leucine transport in rabbit. 1134 57

The present study was primarily done to compare cation-ATPase phosphorylation kinetics with an anion-ATPase's phosphorylation kinetics because of the paucity of information in this area. Utilizing a proteolipsomal preparation containing Cl(-)-ATPase from Aplysia gut, it was demonstrated that phosphorylation of this P-type ATPase was absolutely dependent upon Mg(2+). In organic phosphate concentrations directly (P(i)) enhanced phosphoprotein formation in the presence of increasing concentrations of Mg(2+). It was also shown that the calculated rate constant for E(1)-P formation was 26/sec. This approximated E(1)-P rate constant values for other electrogenic, uniport P-type ATPases, and therefore it was concluded from the results that the anion-ATPase phosphorylation kinetics did not greatly differ from cation-ATPase phosphorylation kinetics.
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PMID:Phosphorylation of chloride-ATPase reconstituted from Aplysia gut. 1135 35

Na(+)-dependent Cl(-)/HCO exchange activity helps maintain intracellular pH (pH(i)) homeostasis in many invertebrate and vertebrate cell types. Our laboratory cloned and characterized a Na(+)-dependent Cl(-)/HCO exchanger (NDAE1) from Drosophila melanogaster (Romero MF, Henry D, Nelson S, Harte PJ, and Sciortino CM. J Biol Chem 275: 24552--24559, 2000). In the present study we used immunohistochemical and Western blot techniques to characterize the developmental expression, subcellular localization, and tissue distribution of NDAE1 protein in D. melanogaster. We have shown that a polyclonal antibody raised against the NH(2) terminus of NDAE1 (alpha CWR57) recognizes NDAE1 electrophysiologically characterized in Xenopus oocytes. Moreover, our results begin to delineate the NDAE1 topology, i.e., both the NH(2) and COOH termini are intracellular. NDAE1 is expressed throughout Drosophila development in the central and peripheral nervous systems, sensilla, and the alimentary tract (Malpighian tubules, gut, and salivary glands). Coimmunolabeling of larval tissues with NDAE1 antibody and a monoclonal antibody to the Na(+)-K(+)-ATPase alpha-subunit revealed that the majority of NDAE1 is located at the basolateral membranes of Malpighian tubule cells. These results suggest that NDAE1 may be a key pH(i) regulatory protein and may contribute to basolateral ion transport in epithelia and nervous system of Drosophila.
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PMID:Localization of endogenous and recombinant Na(+)-driven anion exchanger protein NDAE1 from Drosophila melanogaster. 1144 44

The objective of the present study was to determine the alterations in L-leucine intestinal uptake by intravenous administration of Lipopolysaccharide (LPS), which is a constituent of gram negative bacterial, causative agent of sepsis. The amino acid absorption in LPS treated rabbits was reduced compared to the control animals. The LPS effect on the amino acid uptake was due to an inhibition of the Na+-dependent system of transport, through both reduction of the apparent capacity transport (Vmax) and diminution of the Na+/K-ATPase activity. The results have also shown that the LPS decreases the mucosal to serosal transepithelial flux and the transport across brush border membrane vesicles of L-leucine. The study of possible intracellular mechanisms implicated in the LPS effect, showed that the second messengers calcium, protein kinase C and c-AMP did not play any role in this effect. However, the absence of ion chloride in the incubation medium removes the LPS inhibition and the intracellular tissue water was affected by the LPS treatment. Therefore, the inhibition in the L-leucine intestinal absorption, by intravenous administration of LPS, could be mainly produced by the secretagogue action of this endotoxin on the gut.
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PMID:The administration of lipopolysaccharide, in vivo, induces alteration in L-leucine intestinal absorption. 1183 12

This paper details the results of perfusion experiments examining the accumulation of inorganic and methylmercury (Hg and MMHg) into the gill and intestine tissue of the blue crab, Callinectes sapidus. Additionally, the flux across the tissue to an internal medium, representative of crab tissue or haemolymph, during the perfusion was also measured. The accumulation and transfer processes were studied for each form by exposing the organs to a wide range of Hg and MMHg water concentrations, as well as a mixture of the two Hg forms. Experiments were also performed at different temperatures and in the presence of a metabolic inhibitor to assess the accumulation mechanisms. While the Hg levels bioaccumulated in the two organs were of the same order, the fluxes of Hg from the tissue to the internal medium were slightly higher in the intestine than in the gill. At low external concentrations, the uptake was very similar for both Hg forms, but as exposure pressure increased, inorganic Hg uptake slowed whereas MMHg uptake increased linearly. The results from the perfusion experiments with a mixture of inorganic Hg and MMHg show that while these two forms of Hg do share common uptake pathways, there is also independent uptake. The temperature and inhibition experiments with ouabain, a Na(+)K(+)ATPase inhibitor, show that accumulation is at least partially energy dependent. Overall, the results suggest that there is more than one mechanism of accumulation for both Hg forms. Finally, as accumulation of Hg and MMHg into these tissues was similar, these results contrast with the literature assertion that the enhanced bioaccumulation of MMHg over inorganic Hg is a result of MMHg being more readily transported across the gut membrane.
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PMID:Mercury accumulation and flux across the gills and the intestine of the blue crab (Callinectes sapidus). 1185 78

In lepidopteran larvae, three transport mechanisms are involved in the active and electrogenic K(+) secretion that occurs in the epithelial goblet cells of the midgut. These consist of (i) basolateral K(+) channels, allowing K(+) entry from the haemolymph into the cytosol, (ii) apical electrogenic K(+)/2H(+) antiporters, which are responsible for secondary active extrusion of K(+) from the cell into the gut lumen via the goblet cavity and (iii) apical V-ATPase-type proton pumps. The latter energize apical K(+) exit by building up a large, cavity-positive electrical potential that drives the antiporters. Net K(+) secretion (I(K)) can be measured as short-circuit current (I(sc)) across the in vitro midgut mounted in an Ussing chamber. We investigated the influence of protons on the transepithelial I(K) and the partial reactions of the basolateral K(+) permeability (P(K)) and the apical, lumped 'K(+) pump' current (I(P)) at various extra- and intracellular pH values. In particular, we wanted to know whether increased cellular acidity could counteract the reversible dissociation of the V-ATPase into its V(1) and V(o) parts, as occurs in yeast after glucose deprivation and in the midgut of Manduca sexta during starvation or moulting, thus possibly enhancing K(+) transport. When intact epithelia were perfused with high-[K(+)] (32 mmol l(-1)) salines with different pH values, I(K) was reversibly reduced when pH values fell below 6 on either side of the epithelium. Attempts to modify the intracellular pH by pulsing with NH(4)(+) or propionate showed that intracellular acidification caused a reduction in I(K) similar to that obtained in response to application of external protons. Treatment with azide, a well-known inhibitor of the mitochondrial ATP synthase, had the same effect as pulsing with ammonium or propionate with, however, much faster kinetics and higher reversibility. Breakdown of the basolateral or apical barrier using the antibiotic nystatin allowed the intracellular pH to be clamped to that of the saline facing the nystatin-treated epithelial border. Cell acidification achieved by this manipulation led to a reduction in both apical I(P) and basolateral P(K). The transepithelial I(K) showed an approximately half-maximal reduction at external pH values close to 5 in intact tissues, and a similar reduction in I(P) and P(K) values was seen at an intracellular pH of 5 in nystatin-permeabilised epithelia. Thus, the hypothesized V(1)V(o) stabilization by cell acidity is not reflected in the pH-sensitivity of I(P). Moreover, all components that transport K(+) are synchronously inhibited below pH 6. The significance of our findings for the midgut in vivo is discussed.
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PMID:Insect midgut K(+) secretion: concerted run-down of apical/basolateral transporters with extra-/intracellular acidity. 1189 60

The present study was done primarily to compare cation-ATPase dephosphorylation kinetics with a Cl(-)-ATPase's dephosphorylation kinetics because of the paucity of information in this area. Utilizing a proteoliposomal preparation containing Cl(-)-ATPase from Aplysia gut, it was demonstrated that dephosphorylation of this P-type ATPase was absolutely dependent upon Cl(-). Adenosine triphosphate (ATP) concentrations directly stimulated dephosphorylation of Cl(-)-ATPase in the presence of increasing concentrations of Cl(-). It was also shown that the calculated rate constant for E(1)-P disintegration was 20/sec. This rate constant value approximated E(1)-P rate constant disintegration values for other electrogenic, uniport P-type ATPases. Therefore, it was concluded from these results that the Cl(-)-ATPase dephosphorylation kinetics did not differ greatly from cation-ATPase dephosphorylation kinetics.
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PMID:Chloride-ATPase dephosphorylation in Aplysia gut. 1211 23

The functions of the sarcoplasmic reticulum (SR) in diseased smooth muscle can be investigated by measuring Ca2+ transients in response to agonist application, and through cell homogenization, isolation of microsomes and measurements of Ca-ATPase activity (SERCA). Such measurements have indicated that contractile dysfunction may be associated with degradation of SERCA in some systems, such as hypertrophied bladder smooth muscle. However, the postulated roles of the SR in smooth muscle function vary from one tissue to another and SR may mediate relaxation as well as contraction. Function seems to depend on the precise location of the SR with respect to the plasma membrane and its Ca2+-activated ion channels, the Ca2+ transporters, the cavaeoli, the mitochondria, and the contractile machinery. In diseases characterized by smooth muscle dysfunction, the size of the smooth muscle cells is frequently altered, as occurs in the hypertrophy seen in gut and bladder obstruction and hypertension. This will inevitably lead to alterations in the morphology and the function of the SR. Any therapeutic potential awaits considerable advances in our understanding of the systems in individual smooth muscles and the development of selective drugs.
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PMID:The sarcoplasmic reticulum in disease and smooth muscle dysfunction: therapeutic potential. 1216 12

The bafilomycin A(1) and N-ethylmaleimide (NEM)-sensitive (V-type) ATPase was partially purified from the apical membrane-rich fractions of excretory system (Malpighian tubules and hind gut) of P. bufonius. Enzymatic activity was inhibited by bafilomycin A(1) (IC(50) = 1.3 nM) and NEM (IC(50) = 10.1 microM). The V-type ATPase activity is confined to the apical membrane fraction, while the activity of Na(+)/K(+) -ATPase forms the major part of the basal membrane fraction. The optimal pH required for maximal activity of V-type ATPase was pH 7.5. The effect of 30 mM of various salts on ATPase activity was investigated. NaCl and KCl caused increases of 175% and 184%, respectively. Other chloride salts also caused an increase in activity in the following ascending order: RbCl, LiCI, choline Cl, NaCI, KCl and tris-HCl. The activity of V-type ATPase was stimulated by a variety of different anions and cations, and HCO(3)(-) was found to be the most potent cationic activator of ATPase activity. The present results show that the properties of V-type ATPase of P. bufonius are similar to those reported for other insect tissues.
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PMID:Properties of the V-type ATPase from the excretory system of the usherhopper, Poekilocerus bufonius. 1221 49


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