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)

Clonal line NN hamster astroblasts and clonal line N18 neuroblasts were treated with phospholipase C-free, protease-free, and hemolysin-free Clostridium perfringens sialidase, at a low level (5 X 10(-3) units/ml) so as to maintain cell intactness and to avoid spurious protein effects. A rapid, regular release of sialic acid was achieved. An approximately 9-fold increase in ecto-pyrophosphatase activity could be brought about by action of C. perfringens sialidase for 10 min. Since the sialidase preparations were employed at a level which gave a very low concentration of extraneous protein, and the preparations were free of demonstrable phospholipase C and protease activities, these effects appear to relate specifically to removal of cell surface sialic acid. Neutral p-nitrophenyl phosphatase was activated under the same conditions, but activity remained low compared with pyrophosphatase. Progress curves for activation of the two enzymes were dissimilar. Ecto-pyrophosphatase of NN and N18 cells had an absolute requirement for Mg2+ both before and after removal of cell surface sialic acid. In the presence of near optimum Mg2+ (5 mM), other divalent cations were inhibitory at a low level (10(-1)mM). The effect of Mg2+ concentration, as well as inorganic pyrophosphate concentration, upon ecto-pyrophosphatase activity was shown to obey Michaelis-Menten kinetics for the control activity and for the sialidase-enhanced activity of both cell types. Km for Mg2+ and for pyrophosphate remained constant upon ecto-pyrophosphatase enhancement by sialic acid removal; increase in enzymatic activity was accounted for entirely by an increase in Vmax.
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PMID:Properties of ecto-(inoganic) pyrophosphatase of nervous system cells in culture. Activation upon partial release of sialic acid from the cell surface. 124 85

Cancer-related changes in the serum seromucoid fraction are well known. Last year Woodman published an interesting carbocyanine dye binding method for determination of serum carbohydrate polyanions in sera of normal, traumatized, and tumor-bearing mice. The usefulness of this method for clinical practice has been investigated in this study. Carbocyanine dye-binding polyanion (CPA) and the sialidase-sensitive fraction of this polyanion (SPA) have been determined in sera of 705 human subjects including healthy normal individuals and patients suffering from a broad spectrum of malignant and nonmalignant disease states. Overall, in malignant diseases the CPA and SPA values, in mg pectin equivalents per liter (mean +/-2 S.D.) (292 +/- 111 and 135 +/- 68, respectively) were significantly higher than in the serum from normal controls (166 +/- 33; 74 +/- 18) and patients hospitalized with a variety of nonmalignant disease (195 +/- 56; 92 +/- 36). The highest CPA and SPA values were found in gynecological (331 +/- 117; 149 +/- 69), bronchial (294 +/- 72; 137 +/- 51), and gastrointestinal cancers (316 +/- 111; 154 +/- 69). Elevated CPA values were found in 59.9% and elevated SPA values in 52.8% of patients suffering from malignant diseases. Successfully, radically treated cancer patients with no detectable residues or metastases for at least 1 year had values (186 +/- 39; 76 +/-24) almost within the normal ranges (93 to 250 mg pectin equivalents per liter for CPA and 35 to 120 mg pectin equivalents per liter for SPA).
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PMID:Determination of carbocyanine dye-binding polyanions in malignant and nonmalignant disease states. 127 85

Combined models of cytokine-induced inflammation in the skin and spinal cord of the rat were utilised to demonstrate in vivo that circulating lymphocytes depend upon sialylated adhesion molecules on their surface for maximal recruitment into inflammatory sites in both tissues. When radiolabelled normal spleen cells were incubated with sialidase from Vibrio cholerae or Clostridium perfringens, or with the specific sialic acid-binding lectin from Limax flavus, prior to being washed and injected intravenously into rats, they accumulated significantly less than untreated control cells into tumor necrosis factor (TNF)-activated spinal cord and skin. Pretreatment of splenocytes with sialidase plus the competitive inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DDN) partially restored the accumulation of radiolabelled cells at both inflammatory sites, providing evidence for the specificity of sialidase treatment and the importance of sialyl residues. Pretreatment of macrophage-depleted spleen lymphocytes, or ovalbumin-specific W3/25+ (CD4) cell line T lymphocytes with sialidase produced similar decrements in accumulation at inflammatory sites, demonstrating that lymphocytes, including memory T cells, were relying on sialyl ligands for maximal recruitment. Results from this in vivo study are interpreted as providing indirect evidence that inducible sialyl-binding molecules, probably of the 'selectin' type, occur to a functionally significant extent on activated central nervous system (CNS) endothelium. We speculate that such carbohydrate-binding adhesion molecules may play an important role in the recruitment of inflammatory cells during the formation of CNS lesions in diseases such as the encephalomyelitides and multiple sclerosis.
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PMID:Sialyl ligands facilitate lymphocyte accumulation during inflammation of the central nervous system. 128 23

Trypanosoma cruzi trypomastigotes acquire sialic acid (SA) from host glycoconjugates by means of a plasma membrane-associated trans-sialidase (TS). Here we study the substrate specificity of TS, which differs from all known sialyltransferases in that it does not require cytidine monophosphate (CMP)-SA as donor. The T. cruzi TS reversibly transfers SA to saccharides with terminal beta-Gal (but not alpha-Gal) residues. Donors are saccharides with SA linked to terminal beta-Gal residues by (alpha 2-3), but not (alpha 2-6) bonds. The type of beta-linkage of the terminal Gal residue is of minor importance (beta 1-4 and beta 1-6 are slightly better than beta 1-3), whereas chain length and the structure of additional vicinal sugar residues are not relevant. SA on the surface of living trypomastigotes of T. cruzi is transferred back and forth between the parasite surface and acceptor molecules with terminal beta-Gal, either in solution or on the surface of neighbouring mammalian cells. Addition of fucose residue on or close to the terminal galactose impairs TS activity. As a consequence, the enzyme acts poorly on the E-selectin ligand sialyl-Lewisx and its precursor Lewisx, and in vitro adhesion of TS-treated neutrophils to L-cells expressing L-selectin is not affected. Modifications in the structure of the (alpha 2-3)-linked N-acetyl-neuraminic acid (Neu5Ac) (deoxy or methoxy) of the donor molecules do not impair transfer if the changes are at C9, whereas changes at C4, C7 and C8 impair the ability to donate the modified SA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Substrate specificity of the Trypanosoma cruzi trans-sialidase. 128 52

Previously, we reported that the epitope of a 54-kDa sperm surface sialoglycoprotein on the flagellum is masked by sialic acid residues. The epitope is referred to as a hidden determinant or cryptodeterminant. This paper reports the manner in which the epitope is masked as evaluated qualitatively and quantitatively by means of SDS-PAGE/immunoblots (Western blot) and ELISA. Immunoblotting with four specific monoclonal antibodies to the 54-kDa sialoglycoprotein--T21 (IgM), MC71 (IgG1), MC81 (IgM), and MC91 (IgM)--demonstrated that not only IgM but also IgG antibody MC71 and the Fab fragment MC71 are masked. Quantitative evaluation with ELISA to compare the antibody titration curves of the masked and unmasked antigens on sialidase-treated and untreated sperm, respectively, indicated that sialidase caused the antibody-binding ability of the epitopes to increase to a different level for each antibody. There were 32-256-, 8-16-, 16-, and 2-4-fold increases in binding to T21, MC71, MC81, and MC91 antibodies, respectively. These results suggest that the antigen-masking through the cryptodeterminant does not depend upon the subtype or the molecular mass of the antibody, but upon the biochemical nature of the epitope region that is closely related to the sialic acid. The mechanism and physiological roles of the antigen-masking are discussed.
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PMID:Masking the cryptodeterminant on the 54-kilodalton mouse sperm surface antigen. 128 29

The accumulation of desialylated radiolabelled normal spleen cells and non-neuroantigen specific CD4 T-lymphocytes was measured in the lumbosacral spinal cord of Lewis rats with autoimmune encephalomyelitis (EAE) induced with myelin basic protein in Freund's adjuvant. The labelled cells were preincubated with sialidase and thoroughly washed prior to intravenous injection into rats exhibiting early clinical signs of EAE. Four hours later, the rats were killed and blood and spinal cord samples were radioassayed. Compared with untreated cells, desialylation markedly reduced the accumulation of both normal spleen cells and memory T-lymphocytes in the spinal cord, despite similar levels of cells being present in the blood. In another experiment, the accumulation of desialylated, macrophage-depleted spleen lymphocytes was measured during the onset, recovery and short-term "relapse" phases of acute EAE. Again, compared with controls the accumulation of desialylated lymphocytes was always significantly less, despite similar numbers of cells in the circulation. Lastly, intravenous injections of sialidase produced delayed onset of both clinical and histological signs in rats with passively-transferred EAE. These data confirm and extend previous findings, using a different animal model, that sialyl residues on the lymphocyte surface are important to the accumulation of such cells at inflammatory sites in the central nervous system. The possible relevance of these findings to human demyelinating disease is discussed.
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PMID:Lymphocytes utilise sialylated surface molecules to accumulate in developing lesions of autoimmune encephalomyelitis. 128 78

The specificity of the anti A+N lectin of Moluccella laevis (MLL) was examined by hemagglutination experiments with enzyme-modified human erythrocytes and by inhibition of hemagglutination. In addition, binding to various glycoproteins and inhibition by different sugars and glycoproteins were examined by enzyme immunoassay with antibodies to the lectin. Treatment of AMM erythrocytes with proteolytic enzymes increased their agglutinability by MLL 4-16-fold; similar treatment of ONN cells decreased their agglutinability 8-16-fold. This is in line with the known location and enzyme sensitivity of A and N specificity determinants. Treatment of the erythrocytes with sialidase increased their agglutinability and abolished the distinction between N and M cells. Hapten inhibition of hemagglutination of AMM and ONN erythrocytes by the lectin, and its binding to glycoproteins measured by enzyme immunoassay, confirmed the high specificity of MLL for N-acetyl-D-galactosamine (200-500 times more than for D-galactose) and suggested the presence of hydrophobic interactions around HO-2 of the D-galactose unit. The methyl alpha-glycosides of D-galactose and of N-acetyl-D-galactosamine were better inhibitors than the corresponding beta-glycosides; this preference was abolished, and sometimes reversed, when the p-nitrophenyl glycosides of the same monosaccharides were tested, stressing again the importance of hydrophobic interactions in the binding of carbohydrates to MLL. The lectin reacted well with ONN substance and with glycophorin A of the N phenotype (GPAN), but did not react with OMM substance or GPAM. The strongest inhibitor was asialo ovine submaxillary mucin, which contains many unsubstituted alpha-D-GalpNAc-(1-->3)-Ser/Thr residues; calculated per N-acetyl-D-galactosamine residue, it was 1500 stronger than free N-acetyl-D-galactosamine. In accordance with this result, it was found that the lectin strongly agglutinates Tn cells. The specificity of MLL can, thus, be defined as anti-Tn, crossreactive with blood types A and N, and with sialosyl-Tn. The N-specificity can best be explained by assuming that GPAN contains a small number of unsubstituted or partially sialylated alpha-D-GalpNAc-(1-->3)-Ser/Thr residues, which are present in smaller proportions, if at all, in GPAM.
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PMID:Immunochemical studies on the combining site of the A + N blood type specific Moluccella laevis lectin. 129 Oct 50

The N-acetyl-9-O-acetylneuraminic acid-alpha-p-aminophenylthioketoside 7 was synthesized as a sialidase-stable ligand for the affinity chromatography of a lectin with preferential affinity to O-acetylated sialic acids. The thioketoside was prepared by phase-transfer-catalysed glycosidation followed by Zemplen deacetylation. Regioselective acetylation of the completely de-O-acetylated derivative was practised by two different methods. The acetylation with trimethylorthoacetate did not show the desired selectivity for hydroxyl groups; in addition to the acetylation in position 9 extensive formation of an acetimidate ester derivative with the amino-group in the aminophenyl-moiety was observed. However the esterification with N,N-dimethylacetamide dimethyl acetal resulted in an exclusive acetylation of the hydroxyl-group in position 9. After catalytic hydrogenation this ligand was immobilized both directly and by a six-carbon long spacer group to the agarose matrix. The adsorbents were applied in the affinity chromatography of the lectin and their binding capacity and selectivity compared to those of the formerly used mucin matrix. In both respects the thioketoside coupled by the spacer turned out to be a better ligand for the isolation of the lectin than the mucin.
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PMID:Synthesis of N-acetyl-9-O-acetylneuraminic acid alpha-p-amino-phenylthioketoside and its application as ligand in the affinity chromatography of a lectin with preferential affinity to O-acetylated sialic acids. 129 10

The sialidase from Salmonella typhimurium LT2 was characterized by using photoaffinity-labelling techniques. The well-known sialidase inhibitor 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non- 2-enonic acid (Neu5Ac2en) was modified to contain an amino group at C-9, which permitted the incorporation of 4-azidosalicylic acid in amide linkage at this position. Labelling of the purified protein with the radioactive (125I) photoprobe was determined to be highly specific for a region within the active-site cavity. This conclusion was based on the observation that the competitive inhibitor Neu5Ac2en in the photolysis mixture prevented labelling of the protein. In contrast, compounds with structural and chemical features similar to the probe and Neu5Ac2en, but which were not competitive enzyme inhibitors, did not affect the photolabelling of the protein. The peptide interacting with the probe was identified by CNBr treatment of the labelled protein, followed by N-terminal sequence analysis. Inspection of the primary structure of the protein, predicted from the cloned structural gene for the sialidase [Hoyer, Hamilton, Steenbergen & Vimr (1992) Mol. Microbiol. 6, 873-884] revealed that the label was incorporated into a 9.6 kDa fragment situated within the terminal third of the molecule near the C-terminal end. Secondary-structural predictions using the Garnier-Robson algorithm [Garnier, Osguthorpe & Robson (1978) J. Mol. Biol. 120, 97-120] of the labelled peptide revealed a structural similarity to the active site of influenza-A- and Sendai-HN-virus sialidases with a repetitive series of alternating beta-sheets connected with loops.
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PMID:Photolabelling of Salmonella typhimurium LT2 sialidase. Identification of a peptide with a predicted structural similarity to the active sites of influenza-virus sialidases. 129 92

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


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