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 adhesion of HT29 human colon adenocarcinoma cells to different extracellular matrix components was studied. While treatment of the cells with sialidase had no detectable effect on binding to laminin and fibronectin, attachment to collagen IV was decreased. However, additional removal of beta-(1-4)-bound galactose led to significantly reduced binding to all of the substrates, including fibronectin and laminin. Tunicamycin treatment, monitored by lectin-induced aggregation, drastically diminished cell adhesion to laminin and fibronectin, whereas cell binding to collagen IV was not affected. Arg-Gly-Asp (RGD)-related peptides were used to study the adhesion to collagen IV. The results show that a serine-containing RGD-related peptide GRGDSP has virtually no effect on colon carcinoma cell adhesion to type IV collagen. In contrast, when serine was substituted for threonine (GRGDTP) adhesion to collagen IV was strongly inhibited. After incubation of sialidase-treated cells with the threonine-containing peptide adhesion was almost totally blocked. These results demonstrate the existence of both RGD-dependent and carbohydrate-based mechanisms for metastatic human HT29 cell binding to collagen IV.
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PMID:Alterations in cell surface carbohydrate composition of a human colon carcinoma cell line affect adhesion to extracellular matrix components. 157 4

Two mucins were isolated from bovine submandibular glands and termed major and minor on a quantitative basis. The major mucin representing over 80% of the total glycoprotein fraction contained 37% of its dry weight as protein in contrast to 62% for the minor mucin. Differences in the amino acid composition reflected the higher proportion of typically non-glycosylated peptide in the minor mucin. The molar ratio of N-acetylgalactosamine to serine plus threonine was 0.82 in major and 0.65 in minor mucins, indicating a lower degree of substitution of potential glycosylation sites in the minor mucin. Differences in the carbohydrate composition were found largely related to the sialic acids, with higher relative amounts of N-glycoloylneuraminic acid in the minor mucin. In addition, the proportion of di-O-acetylated sialic acids was higher in the major mucin. The rate of sialidase action on the two mucins could be correlated with the content of N-glycoloylneuraminic acid in each glycoprotein. There was no difference in the type of oligosaccharide found in each mucin and the differences in relative proportions reflected the monosaccharide composition for the two mucins. Gel filtration on Sepharose CL 2B showed a lower molecular weight distribution for the minor in contrast to the major mucin which was partially excluded. Density gradient centrifugation reflected this variation. SDS-PAGE demonstrated a regular banding pattern for the major mucin with a lowest subunit size of 1.8 x 10(5) Da and aggregates in excess of 10(6) Da, while the minor mucin ranged from 3.0 x 10(5) to 10(6) Da. The chemical composition of the isolated mucins was compared with previous histochemical analysis of mucin distribution in bovine submandibular glands and indicates a possible cellular location for each mucin.
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PMID:Characterization of the major and minor mucus glycoproteins from bovine submandibular gland. 184 75

Two monoclonal antibodies, NCC-LU-35 and NCC-LU-81, have been established after immunization of mice with membrane preparations of human lung cancer Lu65 tumor xenograft cells grown in vivo and intact cells cultured in vitro, respectively. These two antibodies react specifically with a majority of human adenocarcinomas, irrespective of the host's blood group ABO status, as well as with normal tissues and erythrocytes of blood group A individuals. The antigenicity is associated with a high molecular weight mucin-like glycoprotein separated by gel filtration of Lu65 tumor extracts. The epitope of the mucin-like glycoprotein has been identified as alpha-N-acetylgalactosaminyl residue directly linked O-glycosidically to serine or threonine residues of polypeptides. This epitope was serologically detected several years ago and given the name Tn. Our identification of the epitope is based on the following results: The antigen is sensitive to alpha-N-acetylgalactosaminidase, but not to sialidase or alpha-fucosidase. Various mono- and difucosyl A determinants, either type 1 or type 2 chain, cross-react with both antibodies. The reactivity with both antibodies can be created by treatment of glycophorin A of normal erythrocytes with sialidase followed by beta-galactosidase. N-[3H]acetylgalactosamine can be released by galactose oxidase/NaB3H4 treatment from the Lu65 mucin-like glycoprotein but not from the mucin-like glycoprotein of normal colonic mucosa upon reductive beta-elimination (alkaline borohydride treatment). The antigen may be one of the tumor-associated A cross-reacting antigens occurring in a wide variety of human adenocarcinomas of hosts belonging to all ABO blood groups.
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PMID:Blood group A cross-reacting epitope defined by monoclonal antibodies NCC-LU-35 and -81 expressed in cancer of blood group O or B individuals: its identification as Tn antigen. 241 56

Histochemical analyses of the chemical structures of sugar sequences with or without blood group specificity were carried out by combined stepwise digestion of tissue sections with exo- and endoglycosidases and subsequent lectin stainings in formalin-fixed, paraffin-embedded human pancreas. In acinar cells from blood group A or AB secretor individuals, sequential digestion with alpha-N-acetylgalactosaminidase and alpha-L-fucosidase imparted reactivity with peanut agglutinin (PNA) in cells reactive with Dolichos biflorus agglutinin as well as those with Ulex europaeus agglutinin I(UEA-I). Simple fucosidase digestion imparted the PNA reactivity only in UEA-I reactive cells. Sequential digestion with alpha-galactosidase and fucosidase likewise liberated the PNA binding sites in Griffonia simplicifolia agglutinin I-B4 reactive cells from blood group B and AB secretors. Sialidase digestion liberated the PNA binding sites not only in acinar cells but also intercalated duct cells, islet cells of Langerhans and endothelial cells. The PNA reactivity obtained by these enzyme digestions was eliminted by endo-alpha-N-acetylgalactosaminidase (endo-GalNAcdase) digestion. Preexisting PNA affinity in acinar cells from non-secretors was also susceptible to endo-GalNAcdase treatment. Following the endo-GalNAcdase digestion, fucosidase or sialidase digestion recovered the PNA reactivity in acinar cells from nonsecretors. These results show that ABH determinants carried on O-glycosidically linked type 3 chain (D-galactose-(beta 1-3)-N-acetyl-D-galactosamine alpha 1-serine or threonine) are secreted in pancreatic acinar cells and suggest that product coded by the secretor gene is required for the complete conversion of type 3 precursor chains into H determinants.
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PMID:Histochemical demonstration of O-glycosidically linked, type 3 based ABH antigens in human pancreas using lectin staining and glycosidase digestion procedures. 247 5

Using lectin staining methods in combination with exo- and endo-glycosidase digestion procedures, we analyzed the chemical structure of different types of blood group-related substances in serous cells of formalin-fixed, paraffin-embedded human submandibular glands. Serous cells produced only H antigen; A and B antigens were not present, and the expression of H antigen is dependent on the secretor status of the tissue donor. Although reactivity with Ulex europaeus agglutinin I (UEA-I) was not markedly reduced by alpha-L-fucosidase digestion, an affinity for peanut agglutinin (PNA) was seen after fucosidase digestion in the cells from secretors. In those from nonsecretors, no PNA reactivity appeared after enzyme digestion. On the other hand, sialidase digestion elicited PNA reactivity in serous cells irrespective of the donor's secretor status. PNA reactivity observed after fucosidase or sialidase digestion was susceptible to endo-alpha-N-acetylgalactosaminidase (endo-GalNAc-dase) digestion. SBA reactivity in UEA-I-negative cells from secretors, or in cells from fetuses and newborn infants, was markedly reduced by beta-galactosidase digestion. After galactosidase digestion, reactivity with Griffonia simplicifolia agglutinin II (GSA-II) appeared in the corresponding cells. This GSA-II reactivity was almost completely eliminated by subsequent beta-N-acetylhexosaminidase digestion. Whereas PNA reactivity in these cells was not reduced by beta-galactosidase treatment, it was significantly diminished by endo-GalNAc-dase digestion. These results suggest that at least two kinds of precursor disaccharides are produced in submandibular serous cells, i.e., SBA-reactive D-galactose-(beta 1-3,4)-N-acetyl-D-glucosamine and PNA-reactive D-galactose-(beta 1-3)-N-acetyl-D-galactosamine alpha 1-serine or threonine (O-glycosidically linked Type 3 chain or T antigen). Final fucosylation and synthesis of these two types of precursor chain appear to be under the control of the secretor gene.
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PMID:Histochemical analysis of the chemical structure of blood group-related carbohydrate chains in serous cells of human submandibular glands using lectin staining and glycosidase digestion. 249 20

The biosynthesis and secretion of human interleukin-6 (IL-6) was studied in monocyte cultures stimulated with endotoxin. After labeling with [35S]methionine and immunoprecipitation with a specific antiserum one major (24 kDa) and four minor (27.5, 23.3, 22.5 and 21.8 kDa) molecular mass forms of IL-6 could be found in the cells and media. Incubation of monocyte media with sialidase and subsequently with endo-alpha-N-acetylgalactosaminidase, which cleaves Gal(beta 1-3)Gal-NAc from serine or threonine, led to the formation of only two forms of IL-6 with apparent molecular masses of 25 and 21.8 kDa. The latter had an electrophoretic mobility indistinguishable from that of 125I-labeled recombinant human IL-6. The results suggest that human monocyte IL-6 carries O-glycosidically bound carbohydrates with a Gal(beta 1-3)Gal-NAc core to which only sialic acid is bound. Differences in O-glycosylation are the major cause for the molecular heterogeneity of IL-6. A small part of IL-6 (27.5 kDa form) is in addition N-glycosylated. Incubation of monocytes with tunicamycin and 1-deoxymynnojirimycin and treatment of IL-6 with endoglucosaminidase H suggested that the 27.5 kDa form of IL-6 carries at least one N-linked complex-type oligosaccharide chain.
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PMID:O- and N-glycosylation lead to different molecular mass forms of human monocyte interleukin-6. 252 18

We have studied function and structure of the low density lipoprotein (LDL) receptors in a monensin-resistant (Monr-31) mutant isolated from Chinese hamster ovary (CHO) cells. To assay the ability of the receptor to bind LDL, we employed three methods, 125I-LDL binding to the cells at 4 degrees C, 125I-LDL binding to the receptor-phospholipid complex (Schneider, W.J., Goldstein, J.L., and Brown, M.S. (1980) J. Biol. Chem. 255, 11442-11447), and ligand blotting (Daniel, T.O., Schneider, W.J., Goldstein, J.L., and Brown, M.S. (1983) J. Biol. Chem. 258, 4606-4611). The LDL receptor number was similar in both CHO and Monr-31, but the binding affinity was reduced in the mutant. The semi-quantitative immunoblotting assay with an antibody directed against the COOH-terminal 14 amino acids and the ligand-blotting assay with LDL also showed that the relative steady-state level of the receptor in Monr-31 was comparable to that in CHO, whereas the binding capacity of the receptor in Monr-31 was lower than that in CHO. The precursor and degradation forms of the LDL receptors produced in the mutant cells were similar in size to those in the parental cells, but the apparent molecular mass of the mature receptor protein in sodium dodecyl sulfate-polyacrylamide gels was reduced about 5000 daltons in the mutant. These results suggest a structural change at the NH2-terminal LDL binding domain. Tests of the effects of tunicamycin, endo-alpha-N-acetylgalactosaminidase (O-glycanase), and sialidase (neuraminidase) on the molecular size of the mature receptors indicated that the reduced size of the receptor in the mutant cells resulted from altered oligosaccharide chain(s) linked to serine/threonine residues in the binding domain. We compared the molecular sizes and binding activity of human LDL receptors in several clones derived from CHO and Monr-31 cells which were transfected with human LDL receptor cDNA. The human LDL receptors produced in the transfected clones of Monr-31 were also smaller in molecular size and lower in binding capacity than those produced in the transfected clones of CHO. These results suggest that both structural and functional alteration of the LDL receptor of Monr-31 is not caused by a mutation in the structural gene of the LDL receptor but by altered processing or maturation of the receptor. The correlation of the decrease in molecular size and reduced binding capacity of the LDL receptor is discussed.
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PMID:Low binding capacity and altered O-linked glycosylation of low density lipoprotein receptor in a monensin-resistant mutant of Chinese hamster ovary cells. 330 76

gpL115, the surface sialoglycoprotein that is defective in lymphocytes of Wiskott-Aldrich syndrome patients has been purified from large scale cultures of the lymphoblastoid line CEM. The purification entails cell lysis and solubilization of gpL115 with the detergent Nonidet P-40, sequential affinity chromatography on lentil lectin-Sepharose, wheat germ lectin-Sepharose, and, after treatment with sialidase, on peanut lectin-Sepharose. Sepharose CL-6B gel filtration removes residual protein contaminants and transfers asialo-gpL115 from Nonidet P-40-containing to sodium dodecyl sulfate-containing buffer. The yield, 1300 micrograms of homogeneous protein/10(11) cells, represents greater than 60% recovery. The amino acid composition of gpL115 has several atypical features including low lysine content, high proline content, and very high content of hydroxyamino acids (12.5 residues of serine and 12.5 residues of threonine/100 amino acids). Total carbohydrate content of gpL115 is very high, i.e. 52% for the asialo-molecule. The major carbohydrate residues of asialo-gpL115 are galactose and N-acetylgalactosamine in approximately equimolar amounts (25 and 22 residues/100 amino acids, respectively) plus severalfold lower amounts of N-acetylglucosamine, fucose, and mannose.
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PMID:Purification and chemical composition of gpL115, the human lymphocyte surface sialoglycoprotein that is defective in Wiskott-Aldrich syndrome. 371 Oct 98

Newcastle disease virus sialidase was found to exhibit strict specificity for hydrolysis of the NeuAc alpha 2 leads to 3Gal linkage contained in glycoprotein oligosaccharides both N-linked to asparagine and O-linked to threonine or serine under conditions that left oligosaccharides containing the NeuAc alpha 2 leads to 2 leads to 6Gal and NeuAc alpha 2 leads to 6GallNAc linkages intact. This was determined, in part, by examining the viral sialidase for its ability to hydrolyze glycoprotein oligosaccharides derivatized with purified sialyltransferases to contain the [14C]NeuAc alpha 2 leads to 3Gal, [14C]NeuAc alpha 2 leads to 6GalNAc, and [14C]NeuAc alpha 2 leads to 6Gal linkages. The viral sialidase was also tested for hydrolysis of the NeuAc alpha 2 leads to 3Gal and NeuAc alpha 2 leads to 6Gal linkages on the N-linked oligosaccharides of alpha 1-acid glycoprotein. Selective hydrolysis of the NeuAc alpha 2 leads to 3Gal linkage was shown by periodate oxidation and by 500-MHz 1H-NMR spectroscopy of native and sialidase-treated glycopeptides. The NMR spectra, together with composition data, further indicated that the NeuAc alpha 2 leads to 3Gal and NeuAc alpha 2 leads to 6Gal linkages were localized to specific branches of the major tri- and tetraantennary oligosaccharides of alpha 1-acid glycoprotein. The results indicate that the Newcastle disease virus sialidase can initiate the selective degradation of N-linked oligosaccharide branches containing the NeuAc alpha 2 leads to 3Gal linkage.
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PMID:Newcastle disease virus contains a linkage-specific glycoprotein sialidase. Application to the localization of sialic acid residues in N-linked oligosaccharides of alpha 1-acid glycoprotein. 629 Apr 80

Platelet factor 4 is a heparin-binding protein released from the alpha granules of activated platelets. This study describes the purification and identification of two forms of rat platelet factor 4, the previously characterized non-glycosylated form of 7 kDa and an additional glycosylated form of molecular mass 9 kDa. The two proteins both neutralized the antithrombin-III-dependent inhibitory activity of heparin. Although their amino acid composition was found to be the same, in the N-terminal sequence of the 9-kDa protein, the second threonine residue could not be detected and a difference of 976Da was determined by mass spectrometry. After digestion with O-glycanase and sialidase, the two proteins showed the same molecular mass. Overall consideration of these data led to identification of the higher-molecular-mass protein as a glycosylated form of rat platelet factor 4 with O-glycosylation at the second N-terminal amino acid, while the structure of the oligosaccharide core was established by mass spectrometry and sugar differentiation with lectins. The two forms of platelet factor 4 are both present in platelets and secreted after platelet activation.
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PMID:Rat platelets contain glycosylated and non-glycosylated forms of platelet factor 4. Identification and characterization by mass spectrometry. 803 93


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