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)

The electron-microscopic localization of ouabain-sensitive, K-dependent p-nitrophenylphosphatase (K-NPPase) activity of the Na - K-ATPase complex was studied in the exorbital lacrimal gland of the untreated rat with the use of a newly developed one-step lead-citrate method (Mayahara and Ogawa 1980; Mayahara et al. 1980). In the rat lacrimal gland fixed for 15 min in a mixture of 2% paraformaldehyde and 0.25% glutaraldehyde, an electron-dense reaction product was observed on the plasma membrane of the basal infoldings and the lateral interdigitations of the ductal cells. The most intense reaction product - and thus the major site of the Na - K-ATPase activity - was evident on the basolateral membranes of the cells of the large interlobular ducts; a weak reaction was seen on the basolateral, extensively folded plasma membranes of the small intercalated ducts; no reaction product was observed on the plasma membranes of the acinar cells. Addition of 1) 10 mM ouabain, 2) p-chloromercuri-phenyl-sulfonic acid (PCMB-S), 3) elimination of K-ions from the incubation medium, or 4) preheating abolished completely the K-NPPase reaction. The activity was also substrate-dependent. Mg-ATPase-activity was observed not only in the basolateral membranes of all ductal cells but also in the basal part of the acinar cells and on the walls of blood vessels. This reaction was neither inhibited by ouabain nor activated by K-ions. The precipitate of the Mg-ATPase-activity was localized at the extracellular side of the plasma membrane, whereas the K-NPPase-reaction product was restricted to the cytoplasmic side of the plasmalemma. In contrast, non-specific alkaline-phosphatase (ALPase) activity was missing in cells of the large interlobular ducts, but obvious on the apical plasmalemma of cells lining the small intercalated ducts. With respect to its localization and reactivity pattern the activity of the K-NPPase (member of the Na - K-ATase complex) differs markedly from the Mg-ATPase- and ALPase-activity.
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PMID:Ultracytochemical localization of ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase activity in the lacrimal gland of the rat. 614 Oct 8

C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed saturation kinetics with increasing 67Cu concentration. The Michaelis constant (Km) for uptake was 0.63 +/- 0.14 microM; maximum velocity (Vmax) was 3.29 +/- 0.57 pmol Cu.mg protein-1.min-1. The Km for efflux was 0.15 +/- 0.06 microM; Vmax was 1.08 +/- 0.71 pmol Cu.mg protein-1.min-1. p-Chloromercuribenzoate (p-CMB) totally blocked 67Cu efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the cell after 50 min was partitioned equally between particulate and soluble fractions. p-CMB-treated cells accumulated more 67Cu, but < 10% was bound to the particulate (membrane) fraction. Pb also increased 67Cu accumulation without affecting Km and Vmax of 67Cu uptake. These data suggest that carriers for import and export of Cu in C6 cells are distinct or operate in two different cellular environments. Efflux is a sulfhydryl-dependent process subject to inhibition by Pb. The data are consistent with a P-type ATPase in the efflux of Cu from cells and the potential for Pb to inhibit the efflux mechanism.
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PMID:Copper transport and kinetics in cultured C6 rat glioma cells. 748 58

Localization of the PCMB-R spin label and benzocarboline probe bound with the purified preparation of pig kidney-Na+, K(+)-ATPase relative to active site of the enzyme was studied by EPR method. The number of Mn2+ ions in active site of the enzyme as well as that bound with lipids was determined from EPR spectra of paramagnetic manganese ions replacing magnesium ions were measured in frozen protein samples of Na2+, K(+)-ATPase at 77 K. It has been found that sulfhydryl group of the enzyme modified by PCMB-R and benzocarboline probe are placed at distances 38 A and 50 A, respectively, from Mn2+ ions in the active site of Na+, K(+)-ATPase. Evaluation of the immersion depth of the nitroxyl radical into protein globule showed that benzocarboline probe was immobilized near the macromolecular protein surface; there are two bound probe sites, distinguished by accessibility of ferricyanide ions.
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PMID:[Interaction of spin labels and probes with Na+,K+-ATPase]. 829 Nov 40

It has been shown, less concentrations of p-chlormercuribenzoate (1 and 2.5 mM) increased Ca2+ content in gland tissue and thereby protein secretion level that may occurred mainly by suppression Ca(2+)-pump or/and stimulation of Na(+)-Ca(2+)-exchange (both in cell plasma membrane) through modulation of SH-groups which form part of their molecules. Higher PCMB concentrations markedly decreased Ca2+ content in gland tissue as well as protein secretion. Effects of PCMB (5 and 10 mM), depending on the direction of Na(+)-Ca(2+)-exchange functioning (Ca(2+)-efflux or Ca(2+)-influx), were evoked or presumably by suppression of endoplasma reticulum Ca(2+)-pump (at conditions Na(+)-dependent Ca(2+)-efflux) or Na(+)-dependent Ca(2+)-influx into the cells that clearly confirmed when PCMB was added on the background of eosin Y (specific Ca(2+)-ATPase inhibitor). Possible role of potential dependent Ca(2+)-channnels in the mediating of PCMB effects is discussed. Introducing of dythiothreitol (DTT) increased Ca2+ content in glands and decreased secretion level obviously by protection of SH-groups of cell Ca(2+)-transporting systems and thereby diminished [Ca2+]i. Finally, we confirm important functional role of SH-groups in the regulation of Ca(2+)-homeostasis in secretory cells of exocrine glands.
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PMID:[Effect of p-chloromercuribenzoic acid and dithiothreitol on the Ca(2+) content of salivary glands and their protein secretion]. 1151 48

Phosphatase activities associated with the intestinal brush border membrane (BBM) of the rat were examined histochemically in relation to the characteristic environment of the intestine, where luminal pH fluctuates drastically between alkaline and acid pH ranges. Special attention was given to intestinal alkaline phosphatase (IALP) and phytase on the BBM. Whole body fresh-frozen sections of young rats and their rapidly frozen and freeze-substituted small intestines, embedded in Technovit 7100, were processed for the histochemical demonstration of phosphatase activity at three different pH values (9.2, 7.3, and 5.2), representing the deviation of luminal pH in vivo. Either an azo-dye method or lead-salt method was employed using naphthol AS-MX phosphate and ATP as substrate, respectively. With the azo-dye method, intense phosphatase reactions were demonstrated along the BBM at all three pH ranges. Phosphatase reactions of the BBM at pH 9.2 and 7.3 were abolished by L(+)-phenylalanine, heat pre-treatment, and EDTA chelation although some reaction remained at pH 7.3 after the treatment with EDTA or L(+)-phenylalanine. Phosphatase reactions of the BBM at pH 5.2 were resistant to L(+)-phenylalanine, L(+)-tartrate, PCMB and EDTA chelation, implying that the characteristics of the enzyme responsible for phosphohydrolysis at acid pH values differed from those at higher pH values. The lead-salt method in which ATP was used as substrate revealed intense reactions--which were dependent on Mg++ and stimulated by Ca++ and resistant to L(+)phenylalanine--to be localized along the BBM at alkaline and neutral pH values, but not at acid pH values. In vitro experiments showed progressive hydrolysis of naphthol AS-MX phosphate by purified phytase at pH 5.2, in a dose-dependent manner, and suggested the possible involvement of phytase in the phosphatase reactions of the BBM at acid pH. These data indicate that the phosphatase reactions at alkaline and neutral pH values, associated with the BBM of the rat intestine, represent IALP and Mg++/ Ca++-ATPase, while those at acid pH appear to correspond to phytase activity, something which has not been demonstrated by histochemical methods despite the availability of extensive data based on biochemical analyses.
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PMID:Phosphatase activities of rat intestinal enterocytes and their relation to diverse luminal pH, with special references to the possible localization of phytase along the brush border membrane. 1183 8

Mammalian aquaporin 1 (AQP1) is well known to function as a membrane channel for H2O and CO2 transport. Zebrafish AQP1a.1 (the homologue of mammalian AQP1) was recently identified in ionocytes of embryos; however its role in ionocytes is still unclear. In this study, we hypothesized that zebrafish AQP1a.1 is involved in the acid secretion by ionocytes through facilitating H2O and CO2 diffusion. A real-time PCR showed that mRNA levels of AQP1a.1 in embryos were induced by exposure to 1% CO2 hypercapnia for 3 days. In situ hybridization and immunohistochemistry showed that the AQP1a.1 transcript was highly expressed by acid-secreting ionocytes, i.e., H+-ATPase-rich (HR) cells. A scanning ion-selective electrode technique (SIET) was applied to analyze CO2-induced H+ secretion by individual ionocytes in embryos. H+ secretion by HR cells remarkably increased after a transient loading of CO2 (1% for 10 min). AQP1a.1 knockdown with morpholino oligonucleotides decreased the H+ secretion of HR cells by about half and limited the CO2 stimulated increase. In addition, exposure to an AQP inhibitor (PCMB) for 10 min also suppressed CO2-induced H+ secretion. Results from this study support our hypothesis and provide in vivo evidence of the physiological role of AQP1 in CO2 transport.
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PMID:Aquaporin 1 Is Involved in Acid Secretion by Ionocytes of Zebrafish Embryos through Facilitating CO2 Transport. 2628 15


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