Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sarcolemmal membranes were isolated by the hypotonic shock-LiBr treatment method from rat, guinea pig, rabbit, and dog hearts and their various biochemical activities were measured. The Mg2+-ATPase, Ca2+-ATPase, and 5'-nucleotidase were most active in rat heart homogenates as well as sarcolemmal membranes, whereas the adenylate cyclase and Na+, K+-ATPase were most active in guinea pig heart preparations. ATP-independent calcium binding activity of rat heart sarcolemma was the same as that of guinea pig heart membrane, whereas ATP-dependent calcium binding of rat heart preparation was negligible. Treatment of sarcolemma with 0.6 M KCl increased the adenylate cyclase and Na+, K+-ATPase activity in rat heart, but these activities were unaltered or decreased in other species. The gel electrophoretic pattern of protein bands and phospholipid composition of rat heart sarcolemma were different from those of guinea pig heart. Sarcolemma isolated from hearts by sucrose gradient method also showed species-dependent difference in the membrane-bound enzyme activities. These results have been interpreted to suggest species-related difference in calcium movements across sarcolemma and this may contribute to determining species-dependent difference in the regulation of myocardial calcium metabolism.
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PMID:Species-related difference in the heart sarcolemmal enzyme activities. 624 42

Basolateral membrane (BLM) enriched fraction was isolated from homogenized rat kidney cortex by differential centrifugation. We also obtained a fraction enriched in plasma membrane (PM). The morphology of the isolated BLM fragments was studied by transmission and freeze fracture electron microscopy. The relative specific activity of Na+-K+-ATPase was enriched 7-fold, while that of marker enzymes for PM, endoplasmic reticulum, and lysosomes was lower than in the crude homogenate. There was a 10-fold difference in the ratios of activities of Na+-k+-ATPase to Mg2+-ATPase in the BLM and in the PM enriched fractions. Kallikrein activity was determined with S-2266 substrate and by radioimmunoassay of kinin released. It was low in the BLM fraction prior to adding detergent, but Triton X-100 increased the activity 12 to 16-fold. Both free trypsin and Sepharose 4B-bound insoluble trypsin increased kallikrein activity 2- to 3-fold in both the membrane-bound and soluble fractions, probably by activating a prekallikrein. The results were interpreted that the kallikrein studied originated from the distal tubular BLM.
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PMID:Kallikrein and prekallikrein on the basolateral membrane of rat kidney tubules. 627 73

(1) A (K+ + H+)-ATPase containing membrane fraction, isolated from pig gastric mucosa, has been further purified by means of zonal electrophoresis, leading to a 20% increase in specific activity and an increase in ratio of (K+ + H+)-ATPase to basal Mg2+-ATPase activity from 9 to 20. (2) The target size of (Na+ + K+)-ATPase, determined by radiation inactivation analysis, is 332 kDa, in excellent agreement with the earlier value of 327 kDa obtained from the subunit composition and subunit molecular weights. This shows that the Kepner-Macey factor of 6.4 X 10(11) is valid for membrane-bound ATPases. (3) The target size of (K+ + H+)-ATPase is 444 kDa, which, in connection with a subunit molecular weight of 110000, suggests a tetrameric assembly of the native enzyme. The ouabain-insensitive K+-stimulated p-nitrophenylphosphatase activity has a target size of 295 kDa. (4) In the presence of added Mg2+ the target sizes of the (K+ + H+)-ATPase and its phosphatase activity are decreased by about 15%, while that for the (Na+ + K+)-ATPase is not significantly changed. This observation is discussed in terms of a Mg2+-induced tightening of the subunits composing the (K+ + H+)-ATPase molecule.
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PMID:Studies on (K+ + H+)-ATPase. VI. Determination on the molecular size by radiation inactivation analysis. 630 21

The effect of hydroxychlorodiphenyl ethers (HO-ClX-DPEs; chlorinated pre- and isopredibenzodioxins), contaminants of technical chlorophenol preparations, on human erythrocyte membrane-bound adenosinetriphosphatases (ATPases) has been investigated. Both 2- and 3-HO-Cl9-DPE inhibited the Na+ + K+-activated, Mg2+-dependent ATPase (Na+, K+, Mg2+-ATPase). The Mg2+-dependent ATPase (Mg2+-ATPase) was stimulated at lower concentration of these compounds, but at higher concentrations there was a gradual decrease in the extent of stimulation, 2-Hydroxy-21, 41, 41-trichlorodiphenyl ether (2-HO-Cl3-DPE; Irgasan DP-300; Triclosan) was not as effective as the nonachloro compounds at inhibiting Na+, K+, Mg2+-ATPase and was inactive at stimulating Mg2+-ATPase. Pure pentachlorophenol (PCP) caused both inhibition of Na+, K+, Mg2+-ATPase and stimulation of Mg2+-ATPase, although each effect required a higher concentration of PCP than was needed for the HO-CL9-DPEs. The possible relationship of the effects of HO-CL x-DPEs on human erythrocyte membrane ATPase activities to the potent hemolytic activity of these compounds is discussed.
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PMID:Effect of hydroxychlorodiphenyl ethers (chlorinated pre-and isopredioxins) on erythrocyte membrane adenosinetriphosphatase activity. 646 Jan 16

Ca2+, Mg2+-ATPase is a membrane-bound enzyme localized at the bile canalicular membranes of hepatocytes. Cytoskeleton and tight junctions are important for maintenance of the polar distribution of plasma membrane proteins. In order to understand the mechanisms involved in the redistribution of Ca2+, Mg2+-ATPase due to cholestasis, the relationship between Ca2+, Mg2+-ATPase, microfilaments and tight junctions was examined. Cholestasis was induced in rat liver by common bile duct ligation (CBDL) for 2 weeks. Localization of Ca2+, Mg2+-ATPase activity was studied at the light and electron microscopic level. Double-staining of the enzyme and F-actin was performed using phase-contrast and fluorescence microscopy of 7-nitrobenzene-2-oxa-1,3-diazole phallacidin (NBD-ph), respectively. Immunofluorescence microscopy of ZO-1 was applied for the observation of tight junctions. Furthermore, cytoskeleton and junctional complexes were investigated electron microscopically in saponin-extracted tissues. The results showed that CBDL induced redistribution of Ca2+, Mg2+-ATPase activity from the apical to the entire plasma membrane of hepatocytes, which seemed to occur independently of F-actin. F-actin was present at all membrane domains of hepatocytes in control liver, whereas CBDL increased the amounts of F-actin mainly at the bile canalicular membranes. An inverse distribution pattern of Ca2+, Mg2+-ATPase activity and F-actin was found in epithelial cells of bile ducts in control and cholestatic livers. Marked alterations in microfilaments were observed at the bile canaliculi, which were defined as hypertrophy and atrophy and were in association with changes in tight junctions. Structural impairment of the tight junctions was proven by disordered immunofluorescence of ZO-1. It is concluded that changes in the distribution of Ca2+, Mg2+-ATPase and F-actin due to CBDL are independent of each other. CBDL-induced disorders of microfilaments are related to impairment of structural integrity of tight junctions that is suggested to be responsible for the redistribution of Ca2+, Mg2+-ATPase in hepatocytes.
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PMID:Redistribution of Ca2+, Mg2+-ATPase activity in relation to alterations of the cytoskeleton and tight junctions in hepatocytes of cholestatic rat liver. 892 66

Despite pronounced differences by which membrane-depolarizing or phospholipase C-activating stimuli initiate contractile responses, a rise in [Ca2+]i is considered the primary mechanism for induction of smooth muscle contractions. Subsequent to the formation of the well-characterized Ca(2+)4-calmodulin complex, interaction with the catalytic subunit of myosin light chain kinase triggers phosphorylation of 20 kDa myosin light chain and activates actin-dependent Mg2+-ATPase activity, which ultimately leads to the development of tension. The present article reviews the fundamental mechanisms leading to an increase in [Ca2+]i and discusses the biochemical processes involved in the transient and sustained phases of contraction. Moreover, the commentary summarizes current knowledge on the modulatory effect of changes in the microviscosity of the plasma membrane on the Ca2+ transient as well as the contractile response of smooth muscle. Evidence has accumulated that these changes in microviscosity alter the activity of membrane-bound enzymes and affect the generation of endogenous mediators responsible for the regulation of cytosolic Ca2+ concentrations and for the [Ca2+]i-sensitivity of myosin light chain phosphorylation.
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PMID:Ca2+ transient, cell volume, and microviscosity of the plasma membrane in smooth muscle. 925 51

Vectorial sorting of plasma membrane protein-containing vesicles is essential for the establishment and maintenance of cell polarity. In the present study, the involvement of altered vesicle transport in the redistribution of membrane-bound Ca2+, Mg2+-ATPase resulting from cholestasis was investigated in hepatocytes. Cholestasis was induced in rat liver by common bile duct ligation. Ca2+, Mg2+-ATPase activity was demonstrated histochemically at the light and electron microscopical levels. Microtubules, an important factor for transcellular transport of vesicles, were studied in situ by immunofluorescence microscopy and electron microscopy in detergent-extracted preparations. The results showed that microtubules underwent significant changes after common bile duct ligation. The most pronounced alteration was focal accumulation of beta-tubulin in the cytoplasm of hepatocytes after 7 days of common bile duct ligation. At the electron microscopical level, the number of microtubules was increased considerably. In control livers, the activity of Ca2+, Mg2+-ATPase was localized only at the apical plasma membrane of hepatocytes, but it was also present at the basolateral plasma membrane after common bile duct ligation. The number of intracellular vesicles containing Ca2+, Mg2+-ATPase activity was increased strikingly, and some of them were associated with lateral membrane domains in which Ca2+, Mg2+-ATPase activity was found. It is concluded that common bile duct ligation induces the rearrangement of microtubules, which may disturb vectorial transport of Ca2+, Mg2+-ATPase-containing vesicles in hepatocytes, leading to the redistribution of Ca2+, Mg2+-ATPase.
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PMID:The involvement of altered vesicle transport in redistribution of Ca2+, Mg2+-ATPase in cholestatic rat liver. 1010 Jul 33

Seven hepatic phosphatases were histochemically investigated in male white rats (Rattus norvegicus) pretreated with chronic subtoxic doses of lead acetate. Lead has increased the activities of alkaline-, acid-, neutral-, adenosine mono- and glucose-6-phosphatase, but has markedly decreased the activity of membrane-bound Na+-K+, ATPase while the activity of mitochondrial Mg2+-ATPase was not altered. It has also produced heterogenous alterations in the distribution patterns, sites of the enzymatic activities and in the intensity of phosphatase activities among the same type of cells in the terminal afferent and efferent venules of the hepatic lobules. The obtained histochemical findings indicate that the alterations in the activities of hepatic phosphatases could be an adaptation to the metabolic, structural and functional changes in the organelles of hepatic cells due to lead intoxication.
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PMID:Histochemical demonstration of changes in the activity of hepatic phosphatases induced by experimental lead poisoning in male white rats (Rattus norvegicus). 1079 82

Mutations of the ABC1 transporter have been identified as the defect in Tangier disease, characterized by low HDL and cholesterol ester accumulation in macrophages. A full-length mouse ABC1 cDNA was used to investigate the mechanisms of lipid efflux to apoA-I or HDL in transfected 293 cells. ABC1 expression markedly increased cellular cholesterol and phospholipid efflux to apoA-I but had only minor effects on lipid efflux to HDL. The increased lipid efflux appears to involve a direct interaction between apoA-I and ABC1, because ABC1 expression substantially increased apoA-I binding at the cell surface, and chemical cross-linking and immunoprecipitation analysis showed that apoA-I binds directly to ABC1. In contrast to scavenger receptor BI (SR-BI), another cell surface molecule capable of facilitating cholesterol efflux, ABC1 preferentially bound lipid-free apoA-I but not HDL. Immunofluorescence confocal microscopy showed that ABC1 is primarily localized on the cell surface. In the absence of apoA-I, cells overexpressing ABC1 displayed a distinctive morphology, characterized by plasma membrane protrusions and resembling echinocytes that form when there are excess lipids in the outer membrane hemileaflet. The studies provide evidence for a direct interaction between ABC1 and apoA-I, but not HDL, indicating that free apoA-I is the metabolic substrate for ABC1. Plasma membrane ABC1 may act as a phospholipid/cholesterol flippase, providing lipid to bound apoA-I, or to the outer membrane hemileaflet.
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PMID:Specific binding of ApoA-I, enhanced cholesterol efflux, and altered plasma membrane morphology in cells expressing ABC1. 1091 65

Three experimental diets with varied n-6-to-n-3 fatty acid ratios (120, 40 and 8) were prepared by a suitable blending of safflower oil containing 72.5% linoleic (18:2 n-6) acid and non-detectable levels of alpha-linolenic (18:3 n-3) acid, and soybean oil having 56.1% linoleic (18:2 n-6) acid and 7.9% alpha-linolenic (18:3 n-3) acid. These diets were fed to weanling female Wistar/NIN (inbred) rats for 16 wk to assess the impact of altered dietary n-6-to-n-3 fatty acid ratio on erythrocyte membrane (EMS) cholesterol, phospholipids, fatty acid composition and activities of membrane-bound enzymes such as Na+,K+-ATPase, Ca2+, Mg2+-ATPase and acetylcholinesterase. Activities of total and ouabain-sensitive-ATPases were significantly higher in the erythrocyte membranes of rats fed diets with a n-6-to-n-3 fatty acid ratio of 40 compared to other groups, whereas the erythrocyte membrane-bound acetylcholinesterase was significantly different among the three groups. The highest and lowest activities for this enzyme were observed in the dietary groups with n-6-to-n-3 fatty acid ratios of 8 and 40 respectively. However, the EMS of rats fed diets with a n-6-to-n-3 fatty acid ratio of 40 alone had significantly higher Ca2+,Mg2+-ATPase compared to those of other two groups. Significant increases were observed in absolute amounts of cholesterol, phospholipids and molar ratio of cholesterol to phospholipids in the EMS of rats fed a diet with a very high 18:2 n-6-to-18:3 n-3 fatty acid ratio (120) as compared to those from the dietary group with 18:2 n-6-to-18:3 n-3 fatty acid ratio (40), which had the lowest levels of cholesterol, phospholipids and cholesterol-to-phospholipid molar ratio. On the other hand, the EMS from rats fed a diet with a very low n-6-to-n-3 fatty acid ratio (8) had significantly lower cholesterol and higher proportions of stearic (18:0), oleic (18:1 n-9), eicosapentaenoic (20:5 n-3), and docosahexaenoic acids, and a higher ratio of docosahexaenoic (22:6 n-3) acid-to-a-linoleic (18:3 n-3) acid compared to the EMS from a very high n-6-to-n-3 fatty acid ratio of 120. Although these changes in EM fatty acid profiles were expected of the respective dietary regimens, the observed changes in the activities of membrane-bound enzymes could have resulted from their interaction with membrane cholesterol, phospholipids and fatty acyl chains.
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PMID:Effect of altered dietary n-6-to-n-3 fatty acid ratio on erythrocyte lipid composition and membrane-bound enzymes. 1265 9


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