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)

Complex carbohydrates on the surfaces of eukaryotic cells are thought to participate in a wide variety of cell-cell interactions. A model system has therefore been developed to study these processes. In the present experiments, the ability of chicken hepatocytes to recognize and adhere to sugars covalently linked to polyacrylamide gels was investigated. The gels were snythesized by two methods. Type I gels were prepared from a co-polymer of an active ester of acrylic acid (N-succinimidyl acrylate), acrylamide, and bisacrylamide. The "activated" polyacrylamide gel was then treated with the desired ligand containing an amino group, such as 6-aminohexyl O- or S-glycoside. Type II gels were formed by treating similar ligands with acryloyl chloride, followed by co-polymerization of the resulting N-substituted acrylamide with acrylamide and N,N'-methylenebisacrylamide. These polyacrylamide derivatives offer many advantages for studies with intact cells. They are not toxic to any cell type studied, can be cast in any desired shape, are transparent and stable over a wide range of pH values, and contain no cationic and low to negligible levels of anionic charge (charged groups can be introduced if desired), and the polyacrylamide matrix is stable to common biological agents such as bacteria and enzymes. In addition, type I gels can be synthesized using a broad range of molecules containing amino groups, such as glycopeptides, proteins, etc. The hepatocytes were prepared by collagenase perfusion of intact chicken livers. The rate and extent of adhesion of the cells to the derivatized gels was determined by measuring lactate dehydrogenase in these cells. This enzyme was also used to assay viability and cell "leakiness." At 37 degrees C, 70 to 100% of the cells adhered within 60 min to gels derivatized with N-acetylglucosamine, i.e. gels derivatized with 6-aminohexyl 2-acetamido-2-deoxy-beta-D-glucopyranoside (or the corresponding thioglycoside). By contrast, less than 5% of the cells adhered to polyacrylamide or to gels derivatized with 6-aminohexanol or the 6-aminohexyl glycosides of beta-D-glucose, beta-D-galactose, alpha-D-mannose, beta-D-maltose, beta-D-melibiose, beta-D-cellobiose, and (alpha or beta)-D-lactose. Kinetic studies with the chicken hepatocytes and N-acetylglucosamine gels showed that cell-gel binding was dependent upon Ca2+ and was decreased at low temperatures. Binding was inhibited by N-acetylglucosamine or by glycosides of this sugar, the most effective inhibitor being orosomucoid (alpha1-acid glycoprotein) pretreated with sialidase and beta-galactosidase. The cell surface receptor(s) involved in this interaction is not known, but may be related or identical to the chicken liver binding protein described by Lunney and Ashwell (Lunney, J., and Ashwell, G. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 341--343). The present results suggest that this model system should prove useful in delineating cell surface interactions with carbohydrates.
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PMID:Adhesion of chicken hepatocytes to polyacrylamide gels derivatized with N-acetylglucosamine. 70 Dec 94

Human leucocyte, lymphoblastoid and fibroblast interferons were separately treated with sialidase and the effect of this on their isoelectric focusing was examined using a system in which full dissociation of complexes occurred. Both leucocyte and lymphoblastoid interferons showed a single form with an isoelectric point which was unaltered by treatment with sialidase. In contrast, fibroblast interferon showed three forms which were reduced to one by treatment with the enzyme.
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PMID:Differences in sialic acid content of human interferons. 70 15

Acid mucins in goblet cells of the duodenum, jejunum and ileum of neonates and infants with cystic fibrosis (CF) and without CF were measured by scanning microdensitometry after alcian blue staining according to the protocol of McCarthy and Reid (1963) which characterises four groups of acidic mucins. In CF infants over 6 mth of age, but not in controls, there was an increase along the gut from duodenum to ileum of both weakly acidic and strongly acidic sulphomucins. In the ileum the increase was in total mucins from 6 mth previously in the same CF patients and this difference could be accounted for by an increase of sialidase-resistant mucins. The increase in sulphomucins was more marked at the tip than at the base of the villi. In CF neonates there was significant difference in the quantities of acidic mucins. The question whether the mucins of CF are chemically abnormal or merely accumulated to an abnormal extent is probably best investigated by analysis of sialidase-resistant mucins and sulphomucins of the ileum and strongly acidic sulphomucins of the duodenum and jejunum in CF infants over 6 mth of age.
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PMID:Acid mucins in human intestinal goblet cells. 74 14

Preparations of ECF-A derived from anaphylactic guinea-pig lung diffusates were subjected to a variety of enzymatic degradations. The enzymes employed had specificityonly for their appropiate subtstates. No effect was found following treatmentwith relatively high doses of trypsin, alpha-chymotrypsin, pronase, alkaline phosphataseand sialidase. In contrast a loss of activity was demonstated in a dose-dependent fashion following incubation with tyrosinase, aryl sulphatase and leucine aminopeptidase, suggesting that ECF-A contains a phenolic hydroxyl group, a sulphate ester anda peptide linkage with a free alpha-amino group.
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PMID:The effect of enzyme digestions on the activity of eosinophil chemotactic factor of anaphylaxis (EFC-A). 80 20

Conventional and scanning electron microscopy of calcigerous renal calculi discloses typical concentric laminations, radial striations and microspherules. Random axial distribution of oxalate crystals and their coating by electron-dense matrix fibers with a definite parallel orientation and cross-linkages are evident. The biochemical relationship of uromucoid to matrix substance A is described. It is suggested that renal sialidase may convert the urinary uromucoid to matrix substance A, whose apatite-covered fibers may be responsible for epitaxial nucleation of some crystal systems. Our studies indicate that the intimate apatite-matrix relationship occurs in the human nephron, probably as an intracellular phenomenon. Subsequent extrusion of these mineralized complexes into the lumen of the nephron (intranephronic calculosis) may, in some instances, represent the initial microanatomic stage of renal calculogenesis.
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PMID:Observations on the ultrastructure and genesis of urinary calculi. 83 98

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

Nuclei isolated from rat liver were purified extensively and then subjected to extraction of glycosaminoglycans by the conventional method with a slight modification including the treatments with amylase, nucleases (DNAase and RNAase), and sialidase in addition to the pronase treatment. The nuclear glycosaminoglycan fraction thus prepared was subjected to chromatography on Dowes 1-X2 (Cl-) and electrophoresis before or after digestion with specific enzymes such as Streptomyces hyaluronidase, chondroitinase ABC and AC. These results together with the results of chemical analyses have revealed that the purified nuclei from rat liver contain glycosaminoglycans equivalent to 0.2-0.3 microgram hexuronic acid per mg DNA. A major component of the nuclear glycosaminoglycans has been identified as hyaluronic acid, while a minor component as chondroitin sulfate A (OR C). Preliminary investigations have shown that most of the nuclear glycosaminoglycans are associated with the chromatin fraction.
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PMID:Isolation and identification of glycosaminoglycans associated with purified nuclei from rat liver. 90 87

Physicochemical characteristics of an anti-LH substance, partially purified from human urine, has been determined. It is an acid-precipitable, sialic acid containing glycoprotein with a molecular weight of 162,000. This substance on mg to mg basis has a 50 fold biological potency when compared to that of the crude gonadotropin inhibiting material. Dialysed human pineal protein extracts also showed anti-LH activity which was not attributed to sialidase activity. Polyacrylamide gel electrophoresis of such pineal extracts revealed a glycoprotein component with the same mobility as that of the urinary anti-LH protein. These observations suggest a possibility that the human pineal gland may be associated either with secretion or storage of this gonadotropin inhibiting entity.
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PMID:Some observations on gonadotropin inhibitor (anti-LH) for human urine--with discussion on its possible source of origin. 91 52

Fragment 1, released from bovine plasma high-molecular-weight kininogen by the action of plasma kallikrein, is a glycopeptide with approximately 3 mol of each of N-acetylgalactosamine, galactose and sialic acid in one molecule. All these sugars were in the T-1 fragment obtained by tryptic digestion of fragment 1. Sialic acid can be completely released from the T-1 fragment by sialidase digestion. When this sialic acid-free T-1 fragment was incubated with purified diplococcal endo-alpha-N-acetylgalactosaminidase, all remaining sugars were released as a disaccharide. By Smith degradation and beta-galactosidase digestion, the structure of this disaccharide was found to be Gal beta 1 leads to 3GalNAc. Methylation analysis of the trisaccharide released from fragment T-1 by alkaline borohydride treatment indicated that all the galactose was obtained as the 2,4,6-tri-O-methyl derivative. Based on this evidence, the complete structure of the carbohydrate moieties of fragment 1 was proposed as Sialyl alpha 2 leads to 3Gal beta 1 leads to 3GalNAc. In addition, small amounts of a tetrasaccharide, Sialyl alpha 2 leads to 3Gal beta 1 leads to 3(Sialyl alpha 2 leads to 6)GalNAc also occurred as a carbohydrate chain of fragment 1.
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PMID:The carbohydrate structure of a glycopeptide released by the action of plasma kallikrein on bovine plasma high-molecular-weight kininogen. 91 96

Lipid analyses in the terminal stage of the disease polyunsaturated fatty acid lipidosis (PFAL), showed a brain very poor in lipids. The concentration of sphingolipids was particularly low: gangliosides of cerebral cortex was only 10% of the control value, and cerebrosides of white matter only 2%. Of the gangliosides, GM1 and GD1 a were reduced more than any other ganglioside fraction. The fatty acid compositions of the phosphoglycerides were the same in cerebral cortex and white matter. Compared with what was found in the controls, ethanolamine phosphoglycerides had much higher proportions of 18:1 and 20:4 (n-6) and much lower proportions of 22:4 (n-6) and 22:6 (n-6) and 22:6 (n-3) in the cerebral cortex. Similar changes in the fatty acid patterns were found in the other phosphoglycerides. It is assumed that in PFAL there is a primary disturbance in the metabolism of arachidonic acid, which leads to a series of secondary changes. The results suggested that the gangliosides GM1 and GD1a, sialidase and phosphoglycerides with dokosahexaenoic acid are confined to the nerve endings.
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PMID:Polyunsaturated fatty acid lipidosis: a new nosological entity. 93 13


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