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:3.1.1.53 (sialidase)
2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sialo compounds in the synaptosomal membranes of young rat brain were specifically labeled in vivo by the intracranial injection of radioactive N-acetylmannosamine. More than 95% of the incorporated label was found in glycosidically bound sialic acid. Specific activities of sialic acid in the synaptic membrane gangliosides G71 (monosialo), GD1a (disialo), and GT1 (trisialo) were similar; labeling in GD1b (disialo) was consistently somewhat higher. The highest specific activity of rat brain sialidase was evenly distributed between "small myelin fragment" and synaptosomal membrane fractions, and ouabain-sensitive (Na+, K+)-ATPase also was concentrated in the latter fraction. The greatest amount of bound sialic acid was found in these subcellular fractions having the highest sialidase activity. A microsomal fraction was discovered to contain a small amount of bound sialic acid with a very high degree of radioactive labeling, but no sialidase. Release of sialic acid from the relatively intact membrane preparations by intrinsic membrane-bound sialidase occurred in two recognizable stages. There was a rapid initial release, complete within 30 min, of approximately equal amounts of lipid- and protein-bound sialic acid, corresponding to roughly half of the enzymatically releasable protein-boudn, and somewhat less than one-third of the lipid-bound, sialic acid. The remainder of the membrane sialidase-susceptible sialic acid was released in a second, slower stage. The intrinsic sialidase released 16 +/- 1% of the total sialoprotein and 31 +/- 1% of the total sialolipid sialic acid. Approximately the same amount of sialic acid is releasable from membrane sialolipid by the action of exogenous Vibrio sialidase; almost twice as much is releasable from sialoglycoprotein by this enzyme as compared with the intrinsic membrane sialidase. Each of the various membrane gangliosides appeared to be equally available to the action of the membrane sialidase. The results of this study indicate that both glycolipid- and glycoprotein-bound sialic acid in the synaptic membrane are releasable in situ by the action of the intrinsic synaptic membrane sialidase, and they suggest that this enzyme may act to modulate the physical properties of the membrane. In addition to influencing the rate of hydrolysis of endogenous membrane sialo compounds by intrinsic sialidase, pH had an effect on availability of protein-bound sialic acid. At acid pH, lipid- and protein-bound sialic acid were similarly available, but near neutral pH, gangliosides appeared to be attacked preferentially.
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PMID:Action of intrinsic sialidase of rat brain synaptic membranes on membrane sialolipid and sialoprotein components in situ. 84 35

A rapid small-scale procedure was set up to obtain highly purified preparations of lysosomes and plasma membranes from the homogenate of cerebellar granule cells differentiated in culture. It consisted in a centrifugation of the postnuclear fraction P2, on a Percoll gradient with formation of an upper and lower band. The upper band, upon centrifugation on 1 M sucrose, produced a light band lying on the top, that constituted the plasma membrane preparation. The upper band constituted the lysosome preparation. The plasma membrane preparation exhibited a 6-fold relative specific activity increase of Na+, K(+)-ATPase and 5'-nucleotidase, with negligible contamination by other subcellular markers; the lysosomal preparation exhibited a 30-fold relative specific activity increase of beta-galactosidase and beta-hexosaminidase, with virtually no contamination by other subcellular markers. Both the lysosome and plasma membrane preparations carried sialidase activity on MUB-NeuNAc and ganglioside GD1a. The sialidase activity on GD1a required the presence of Triton X-100 in both subcellular preparations; the sialidase activity on MUB-NeuNAc was markedly activated by albumin only in the lysosomes. The lysosomal sialidase had a unique optimal pH value, 3.9. The plasma membrane sialidase featured two values of optimal pH, one at 3.9, for both substrates and second at 5.4 and 6.0 for MUB-NeuNAc and GD1a, respectively. It is concluded that cerebellar granule cells differentiated in vitro possess one lysosomal sialidase and two plasma membrane sialidases, all of them active on ganglioside.
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PMID:Dual subcellular localization of sialidase in cultured granule cells differentiated in culture. 130 62

The autoantigen La, a known transcription termination factor of RNA polymerase III, was purified to homogeneity from mouse 3T3 cells and calf thymus by different isolation procedures. The La protein from calf thymus was separated into RNA binding and nonbinding subclasses. The murine La protein and the RNA binding subclass of calf thymus La protein showed ATPase/dATPase activity in the presence of DNA-RNA or RNA-RNA hybrids. A novel monoclonal anti-La antibody (La11G7) and patients' anti-La antibodies immunoadsorbed to homogeneously purified La protein were able to inhibit the enzyme activity of La protein. La protein was able to melt a synthetic DNA-RNA hybrid in a reaction that required ATP hydrolysis. The RNA binding ability of the nonbinding subclass was restored by treatment with sialidase. This treatment also restored the protein's ATP-dependent melting activity.
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PMID:Characterization of the autoantigen La as a nucleic acid-dependent ATPase/dATPase with melting properties. 168 13

A central belief about ethanol is that it acts mainly by partitioning into the lipid bilayer of membranes. Newer ideas focus on the neuronal synapse and suggest that ethanol can allosterically change protein conformation, as is suggested by studies on GABA-receptor-mediated chloride uptake and on (Na(+)-K+)-ATPase. Several studies from my laboratory suggest that ethanol enhances enzymatic cleavage of sialic acid (SA) from gangliosides, and perhaps also glycoproteins, but does so without stimulating enzyme activity, suggesting conformational changes that affect accessibility. I propose a new model for the cell membrane in the synaptic region, which features gangliosides surrounding membrane proteins, with an interspersed film of water creating hydrogen bonds that anchor SA moieties to membrane protein. I believe that we should consider the possibility that an important action of ethanol, and polar anesthetics, is due to hydrophilic, not hydrophobic, properties and the ability to dehydrate the cell-surface microdomain. Our laboratory has recently advanced the theory that ethanol dehydrates a "solvent regulatory site" of membrane (Na(+)-K+)-ATPase. This principle might be extended to other enzymes and receptor proteins, as well as to the accessibility of sialoglycoconjugates to sialidase (neuraminidase). Hydrogen bonding between SA and polar regions of receptor protein, and the conformation on both imposed by it, would surely be changed by minor degrees of dehydration and substitution of alcohol molecules for water. Ethanol, unlike water, can only hydrogen bond "at one end." Displacement of water by ethanol would not only "free" the SA groups and make them more vulnerable to enzymatic cleavage but also could simultaneously change the conformation of receptor protein. Similarly, ethanol may displace water that links the polar heads of phospholipids to polar portions of receptors proteins. Ethanol may have an even more important and direct effect of substituting for hydrogen-bonded water within protein itself.
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PMID:Dehydration: a new alcohol theory. 217 30

A hybridoma cell line producing mouse monoclonal antibody against pig kidney Na,K-ATPase was established. The antibody, named 38 (mAb38, IgG1), was purified from mouse ascites fluid by chromatography on a protein A-Sepharose column. Antigens immobilized on microplate wells with p-benzoquinone were used for titer assays. mAb38 cross-reacted with both dodecyloctaethyleneglycol monoether (C12E8)-solubilized enzyme and membranous sodium dodecyl sulfate (SDS)-treated enzyme from kidney with high affinity (50% binding = 0.6 nM). However, the antibody bound to neither alpha- nor beta-subunit separated by preparative SDS-polyacrylamide gel electrophoresis (PAGE). The stoichiometry of antibody binding to the purified enzyme was estimated to be about 0.86 mol of IgG per mol of alpha beta-protomer. Na,K-ATPase proteins were recovered from a column of mAb38-coupled Affi-Gel by elution with pH 3 buffer when C12E8-solubilized kidney enzyme or detergent extracts of brain microsomes were applied to it, confirming that the mAb is directed to Na,K-ATPase. mAb38 at saturation level concentrations had no effect on kidney Na,K-ATPase activity or on ouabain-sensitive Rb uptake in erythrocytes. In an immunofluorescence study, the antibody bound to intact erythrocytes much more strongly than control IgG1 (mAb50c), but the extent of the antibody binding to inside-out vesicles under hypotonic conditions was lower than that of the control. Most of the antibody binding activity remained when the kidney enzyme was treated with sialidase. These results suggest that this mAb38 was raised against an intact conformation of a cell-surface-exposed site of Na,K-ATPase.
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PMID:Isolation and characterization of a monoclonal antibody against pig kidney sodium- and potassium-activated ATPase. 241 10

Baso-lateral membranes were isolated from the canine and porcine kidney cortex by several different methods currently in use. Sidedness of the isolated membrane vesicles was determined by procedures using 1. ouabain-sensitive (Na+K+)ATPase assays in the presence and in the absence of sodium dodecylsulfate or digitoxigenin plus monensin, 2. (Na+, K+, Mg2+)ATPase assays with valinomycin, 3. sialidase accessibility, and 4. binding of hydrophilic and lipophilic cardiac glycosides. The (Na+K+)ATPase activity in the membrane preparation was increased 10-fold of that found in the crude homogenate. Isolated membrane vesicles, prepared by different techniques, were all found to be overwhelmingly of right-side-out orientation;namely, right-side-out = 51-68%, inside-out = 4-13%, and unsealed vesicles = 26-42%. Results of sidedness determinations by different methods showed a good agreement. Thus, predominantly right-side-out oriented vesicles are formed during conventional isolation procedures for membranes of the kidney cortex.
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PMID:Orientation of vesicles isolated from baso-lateral membranes of renal cortex. 284 58

Cultured A6 epithelial cells from toad kidney form confluent monolayers with tight junctions separating the apical and basolateral membranes. These two membrane domains have distinct compositions and functions. Thus, sodium is actively transported across the epithelia from the apical to basolateral surface via amiloride-inhibitable sodium channels located in the apical membrane. Sodium transport is stimulated by vasopressin, cholera toxin, and 8-bromo-cAMP applied to the basolateral surface where the receptors, adenylate cyclase, and Na+/K+-ATPase are located. In a previous study (Spiegel, S., Blumenthal, R., Fishman, P.H., and Handler, J.S. (1985) Biochim. Biophys. Acta 821, 310-318), we demonstrated that exogenous gangliosides inserted into the apical membrane of A6 epithelia do not redistribute to the basolateral membrane. With the ability to vary selectively the ganglioside composition of the apical membrane, we examined the effects of gangliosides on sodium transport in A6 epithelia. When the apical surface of A6 epithelia were exposed to exogenous gangliosides, sodium transport in response to vasopressin, cholera toxin, and 8-bromo-cAMP was enhanced compared to epithelia not exposed to gangliosides. The effect was observed with bovine brain gangliosides, NeuAc alpha 2----3Gal beta 1----3GalNAc beta 1----4[NeuAc alpha 2----3]Gal beta 1----4Glc beta 1----Cer (GD1a) and Gal beta-1----3GalNAc beta 1----4[NeuAc alpha 2----3]Gal beta 1----4Glc beta 1----Cer (GM1), but not with the less complex ganglioside, Neu-Ac alpha 2----3Gal beta 1----4Glc beta 1----Cer (GM3). We examined A6 cells for endogenous gangliosides and found that, whereas GM3 was a major ganglioside, only trace amounts of GM1 and GD1a were present. Based on cell surface and metabolic labeling studies, these gangliosides were synthesized by the cells and were present on the apical as well as the basolateral surface. Bacterial sialidase, which hydrolyzes more complex gangliosides to GM1, was used to modify the endogenous gangliosides on the apical surface; after sialidase treatment, the epithelia were more responsive to vasopressin, cholera toxin, and 8-bromo-cAMP. Thus, gangliosides may be modulators of sodium channels present in the apical membrane of epithelial cells.
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PMID:Gangliosides modulate sodium transport in cultured toad kidney epithelia. 378 88

The morphology and function of the apical mitochondria-rich cells in the mammalian ductus epididymidis epithelium are revised. These cells are similar in all mammalian species studied. Apical mitochondria-rich cells are scarce (1-5 cells/100 principal cells) and are mainly found in the initial epididymal segments. Their morphology varies from slender cells that extend from the basal lamina to the epididymal lumen, to round cells that protrude into the lumen and are not in contact with the basal lamina. Their cytoplasm is more electron-dense than that of principal cells and contains more mitochondria which, in some species, are surrounded by rough endoplasmic reticulum cisternae. The adluminal cytoplasm displays a few short microvilli and contains many acid phosphatase positive vesicles. Apical mitochondria-rich cells differ from the principal cells in some histochemical features such as: (a) different lectin-staining pattern; (b) more intense reaction to the enzymatic activities: carbonic anhydrase, Ca(2+)-ATPase, peanut-agglutinin-sialidase, NADP dehydrogenase, succinate dehydrogenase, alpha-galactosidase and beta-galactosidase; (c) more intense immunoreaction to several cytokeratin types and to estradiol-related receptor protein; (d) weaker immunoreaction to epithelial membrane antigen and to retinol-binding protein. Although the function of the apical mitochondria-rich cells is still unknown, the following possible functions have been suggested: holocrine secretion; cooperation with the principal cells in epididymal reabsorption of testicular fluid; and acidification of epididymal fluid. Experimental results suggest that differentiation and maintenance of apical mitochondria-rich cells are not under androgen control and that these cells are sensitive to estrogen stimulation.
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PMID:The apical mitochondria-rich cells of the mammalian epididymis. 748 29

The morphofunctional organization of the exocrine cells in the foregut of the red-eared slider turtle, Trachemys scripta, was investigated by histochemistry (PAS, AB pH1.0 and pH 2.5, HID-AB, Bowie), lectin-histochemistry (WGA, SBA, UEA, ConA, PNA, DBA, sialidase-SBA, sialidase-PNA, Paradoxical ConA), and immunohistochemistry (antipepsin, anti-alpha-H+,K+ ATPase) to detect regional differences and verify the existence of an oro-aboral gradient in gastric juice secretion. Observations showed that pharyngeal goblet cells have mucins with terminal residuals of GalNAc and sialic acid. In the oesophagus, sulphomucins in the goblet cells are progressively substituted by sialomucins and no glands are found. Gastric surface cells secrete mostly sialomucins with residuals of GlcNAc and GalNAc. The cardias presents glands with cells secreting mostly sialomucins, differing from the surface ones in having GalNAcalpha1,3GalNAc sequences. The fundus presents complex glands with main and lesser tubules. Cells in the main tubules secrete stable, class-III mucins with sialylated residuals of glucose and/or mannose, GalNAcalpha1, 3GalNAc, and Galbeta1,3GalNAc sequences. In the lesser tubules, the oxynticopeptic cells are found, presenting pepsinogen granules and an affinity to the anti-alpha-H+,K+ ATPase, without any oro-aboral variation. The pyloric glands have a secretion similar to that of the neck cells of the fundic glands, consisting of stable, class-III mucins mostly sialylated with a high heterogeneity of residuals such as glucose and/or mannose, fucose, GlcNAc, and GalNAc. Mucins in the foregut are probably involved in several functions such as lubrication, protection against gastric juice, osmotic regulation to increase intestinal absorption, and protection against microbial injuries.
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PMID:Histochemical and immunohistochemical characterization of exocrine cells in the foregut of the red-eared slider turtle, Trachemys scripta (Emydidae). 1955 90

Phosphatidylethanolamine-ceramide-ethanolaminephosphotransferase catalyses the synthesis of ceramide-phosphoethanolamine, a sphingomyelin analogue, from ceramide and phosphorylethanolamine derived from phosphatidylethanolamine. The location of this transferase in synaptic plasma membrane vesicles from rat brain was studied in comparison with sialidase and (Na(+), K(+))ATPase. Synaptic plasma membrane vesicles were purified by sucrose gradient followed by an aqueous polymer two-phase partitioning system. Most of the vesicles were right-side out scaled as demonstrated by latency of ouabain-sensitive (Na(+), K(+))ATPase activity which was unmasked by preincubation with detergents (deoxycholate, Triton X-100 or sodium dodecyl sulphate). Detergents increased sialidase activity but transferase activity was not affected. In the absence of detergents, preincubation with proteases did not modify ATPase activity but strongly inhibited phosphatidylethanolamine-ceramide-ethanolaminephosphotransferase and sialidase activities. Yet even in the presence of detergents, a part of the active site of the transferase was not accessible to the protease action. Our results suggest that at least a part of the active centre of the transferase is situated on the external side of synaptic plasma membrane vesicles; the other part, which is inaccessible to proteases even in the presence of detergents, is embedded in the membrane interior.
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PMID:Phosphatidylethanolamine-ceramide-ethanolaminephosphotransferase activity in synaptic plasma membrane vesicles: Comparison with sialidase and ouabain-sensitive (Na(+), K(+))ATPase activities. 2050 6


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