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)

More than ten new types of gangliosides, in addition to haematoside and sialosylparagloboside, were isolated from human erythrocyte membranes. These were separated by successive chromatographies on DEAE-Sephadex, on porous silica-gel columns and on thin-layer silica gel as acetylated compounds. Highly potent blood-group-Ii and moderate blood-group-H activities were demonstrated in some of the ganglioside fractions. The gangliosides incorporated into cholesterol/phosphatidylcholine liposomes stoicheiometrically inhibited binding of anti-(blood-group I and i) antibodies to a radioiodinated blood-group-Ii-active glycoprotein. The fraction with the highest blood-group-I-activity, I(g) fraction, behaved like sialosyl-deca- to -dodeca-glycosylceramides on t.l.c. Certain blood-group-I and most of the -i determinants were in partially or completely cryptic form and could be unmasked by sialidase treatment. Thus the I and i antigens, which are known to occur on internal structures of blood-group-ABH-active glycoproteins in secretions, also occur in the interior of the carbohydrate chains of erythrocyte gangliosides.
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PMID:Blood-group-Ii-active gangliosides of human erythrocyte membranes. 68 69

The increase in Concanavalin A (ConA) binding to sarcolemmal membranes of rat skeletal muscle following denervation has been attributed to conformational changes in membrane glycoproteins resulting in the unmasking of previously cryptic ConA binding sites (Leung et al., 1982). In this study, analysis of lectin binding patterns to alpha-fucosidase- or sialidase-treated sarcolemmal membranes reveals that the fucose moieties of carbohydrate structures may be principally involved in the unmasking process. By contrast, sialic acid has no apparent effect on the availability of the number of ConA binding sites, but plays a significant role in the masking of other lectin recognition sites.
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PMID:Denervation-induced changes in lectin binding to sarcolemmal glycoproteins: exposure of cryptic recognition sites. 149 18

Sialidases catalyse the hydrolysis of terminal sialic acid of the carbohydrate moiety of glycoconjugates. Sialic acids play a key role in the expression or masking of antigenic sites and in cell-cell interactions. As an example, removal of sialic acid from the human erythrocyte membrane unmasks underlying molecules such as the specific carbohydrates (Gal-GalNac) of the so-called T or Thomsen-Friedenreich cryptic antigen. A consequence of this, is the recognition of that antigen by natural serum antibodies. Since the T antigen has been shown to be present in the lung, we have investigated the possible presence of sialidase and of specific antibodies to sialidase-treated cells in bronchoalveolar lavage fluids (BALF) from patients with pulmonary sarcoidosis or idiopathic pulmonary fibrosis (IPF). By using a fluorogenic substrate (4-methyl umbelliferyl-alpha-D-N-acetyl sodium neuraminate), we were able to detect a sialidase activity in BALF from eight out of nine patients with IPF and from ten out of thirty-five patients with sarcoidosis. BALF from normal volunteers and serum from both patients and normal volunteers were devoid of activity. BALF sialidase has an optimum pH activity of 5.4, it is not inhibited by EDTA and has a molecular weight close to 21 kD. BALF anti-T antibodies (galactose specific) were detectable in minute amounts in only one out of the nine normal volunteers. By contrast, they were frequently present in BALF from sarcoidosis (77%) or IPF (66%) patients and sarcoidosis patients had a higher mean activity. No correlation was observed between the enzymatic and antibody activities.
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PMID:Sialidase activity and antibodies to sialidase-treated autologous erythrocytes in bronchoalveolar lavages from patients with idiopathic pulmonary fibrosis or sarcoidosis. 318 May 12

The presence of Thomsen-Friedenreich antigen (T-Ag) against bladder mucosa in bladder tumor cases and control individuals was examined by the immunoperoxidase and the immunofluorescein method using labelled lectin. T-Ag was negative in all 15 cases of non-malignant bladder epithelium, and positive on the cell surface after sialidase treatment (cryptic T-Ag positive). In the 37 out of 72 bladder tumor cases, however, cryptic T-Ag was positive, and in the remaining 35 cases T-Ag was positive or negative after sialidase treatment. Furthermore 55 cases which had received the first treatment by TUR-Bt were investigated. Thirteen of the 31 cryptic T-Ag positive cases recurred during observation after operation whereas 22 of the 24 T-Ag positive or cryptic T-Ag negative cases recurred, the rate being significantly higher for the latter. In addition, the disease-free interval was absolutely longer in the cryptic T-Ag positive cases than in T-Ag positive or cryptic T-Ag negative cases. The exploration of T-Ag in bladder cancer may be valuable for predicting the clinical course after TUR-Bt.
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PMID:[The study on Thomsen-Friedenreich antigen in bladder tumor]. 389 52

Ganglio-N-triaosylceramide (GalNAc beta 1 leads to 4Gal beta 1 leads to 4Glc beta 1 leads to 1Cer), a tumor-associated marker for L5178 cells, was previously reported to separate on thin layer chromatography into three distinct bands (bands a, b, and c). The present paper describes the characterization of these bands and the factor that determines the degree of glycolipid exposure at the cell surface and its antigenicity. 1) The resolution of ganglio-N-triaosylceramide into three bands was found to be due to molecules having different fatty acid compositions. Band a contained nervonic (C24:1) and lignoceric (C24:0) acids, band b contained palmitic acid (C16:0), and band c contained alpha-hydroxypalmitic acid. 2) Surface labeling of L5178c127 cells with galactose oxidase/sodium borotritide, followed by fluorography of the isolated glycolipids, revealed that all three bands were exposed on the surface of the cell. However, treatment of cells with sialidase before treatment with galactose oxidase resulted in a 10-fold increase of label incorporated into ganglio-N-triaosylceramide. Since no sialylated form of ganglio-N-triaosylceramide was detected on these cells, and no change in the chemical amount of this glycolipid could be detected, the increase of label into this molecule was due to the exposure by sialidase of a normally cryptic glycolipid. The exposure of ganglio-N-triaosylceramide after sialidase treatment was also reflected by the increased sensitivity of these cells to monoclonal antibodies to the glycolipid and complement after enzyme treatment. Thus, the results provide clear evidence that crypticity, as well as antigenicity, of a membrane glycolipid is determined by the degree of sialylation in a second membrane glycoconjugate.
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PMID:Characterization of tumor-associated ganglio-N-triaosylceramide in mouse lymphoma and the dependency of its exposure and antigenicity on the sialosyl residues of a second glycoconjugate. 618 30

ABH isoantigen of 154 superficial urothelial tumor including 11 carcinoma in situ of the bladder (CIS) was investigated by the avidin-biotin-peroxidase complex (ABC) method, and the results were compared with those obtained by the specific red cell adherence (SRCA) test. T (Thomsen-Friedenreich) antigen, a precursor of other blood group antigen than ABC, was also investigated by ABC method. ABH antigen detected by ABC method seemed to be correlated to tumor grade and recurrence rate, while that by SRCA method did not. Sixty two percent of the low grade papillary bladder tumor of blood group other than O was positive by ABC method. As for the recurrence rate of low grade tumor, 11 of 33 cases (33%) with positive ABH isoantigen showed recurrence, while 13 of 21 cases (62%) without ABH isoantigen did so. In CIS, ABH antigen was deleted in 82 percent using ABC method. ABC method is more sensitive and more specific than SRCA, and the sensitivity was increased in blood O. T antigen, which is expressed in many carcinomas, (defined T(+) by Coon) is usually not detected in normal epithelium. Normally, T antigen is cryptic but can be unmasked with sialidase (cryptic T(+)). The cells which lacked T even after sialidase treatment are called cryptic T(-). We investigated T antigen expression in CIS lesion and ureteropelvic tumor by using T specific lectin (peanut agglutinin). In nine cases of CIS which ABH was negative, cryptic T(+), T(+) and cryptic T(-) were found in three, one and five cases, respectively. In ten cases of high grade ureteropelvic tumor, which ABH was all negative, cryptic T(+) was found in five cases. Of these five cases, three are well over five years after surgery. These data, although preliminary, indicate that, by combining two markers (ABH and T antigen), prognosis of urothelial tumor may be predicted better.
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PMID:[The study of ABH isoantigen and T (Thomsen-Friedenreich) antigen of superficial urothelial tumor]. 653 Feb 8

Gangliosides are implicated in cell signal transduction. Prior to investigating this phenomenon in macrophages, the in situ accessibility of gangliosides to macromolecules was assessed for peritoneal macrophages isolated from normal C3H/HeN and endotoxin-hyporesponsive C3H/HeJ mice. C3H/HeJ resident and thioglycolate-elicited macrophage ganglioside patterns are the same as normal strains, and no strain differences in galactose oxidase accessibility for resident or thioglycolate-elicited macrophage gangliosides were found. The only gangliosides accessible to galactose oxidase in resident macrophages are GM1a structures. In thioglycolate-elicited macrophages, an additional ganglioside is accessible. For Escherichia coli-activated macrophages, where ganglioside distribution differs between strains, a difference in galactose oxidase-accessible gangliosides also exists. Escherichia coli-activated C3H/HeN patterns show three triplets absent in C3H/HeJ patterns. There were no differences in ganglioside accessibility to Vibrio cholerae sialidase between the thioglycolate-elicited C3H/HeJ and C3H/HeN macrophages. However, despite differences in sialidase-sensitive ganglioside content between E.coli-activated macrophages of these strains, sialidase accessibility for E.coli-activated macrophages was also similar. Sialidase-susceptible GM3 was cryptic in either strain under all conditions examined. The accessibility of murine macrophage gangliosides to galactose oxidase or sialidase was independent of their sialic acid species and chain length of the ceramide fatty acid. With the exception of GM3, major murine macrophage gangliosides are accessible in situ to macromolecules, especially to exogenous pathogenic bacterial sialidase which can alter macrophage cell surface characteristics. Altered macrophage ganglioside accessibility appears sometimes as a consequence, but not a cause, of C3H/HeJ endotoxin hyporesponsiveness.
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PMID:In situ accessibility of murine macrophage gangliosides. 777 69

A broad variety of normal human tissues were examined for the expression of Thomsen-Friedenreich (TF)-related histo-blood group antigens, TF (Gal beta 1-3GalNAc alpha 1-R), Tn (TF precursor, GalNAc alpha 1-R), sialosyl-Tn (NeuAc alpha 2-6GalNAc alpha 1-R), considered to be useful in cancer diagnosis and immunotherapy, and sialosyl-TF, the cryptic form of TF. These antigens or, more correctly, glycotopes, were determined by immunohistochemistry with at least two monoclonal antibodies (mAbs) each (except sialosyl-TF) as well as by lectin histochemistry. For a better dissection of sialosyl-TF and TF glycotopes, tissue sections were pretreated with galactose oxidase or the galactose oxidase-Schiff sequence. Staining with mAbs appeared to be more restricted than with the lectins used. Distribution patterns among normal epithelia were different for all four antigens. These antigens were also detected in some non-epithelial tissues. They can be classified in the following sequence according to the frequency of their occurrence in normal tissues: sialosyl-TF > > sialosyl-Tn > Tn > TF. Most of the positively staining sites for TF, Tn, and sialosyl-Tn are located in immunologically privileged areas. The complex results obtained with anti-TF mAbs (after treatment of the tissue sections with sialidase from Vibrio cholerae) and the lectins amaranthin and jacalin revealed a differential distribution of the subtypes of sialosyl-TF [NeuAc alpha 2-3Gal beta 1-3GalNAc alpha 1-R and Gal beta 1-3 (NeuAc alpha 2-6)GalNAc alpha 1-R] in normal human tissues. From our data it can be inferred that TF, Tn, and sialosyl-Tn are promising targets for a cancer vaccine.
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PMID:Thomsen-Friedenreich-related carbohydrate antigens in normal adult human tissues: a systematic and comparative study. 887 80

The identification of the xeno-antigens/xeno-antibodies combinations involved in pig-to-human xenograft rejection is an essential step for understanding this process and for the development of procedures to prevent it. Although it is widely accepted that the terminal disaccharide Galalpha1,3Gal-R is by far the major epitope recognized by human natural antibodies reactive with pig tissues, there is also evidence that other carbohydrate epitopes might be important in xenograft rejection. In an attempt to further improve our knowledge of the repertoire of human natural antibodies with anti-pig specificity we sought to determine whether naturally occurring human anti-beta-galactose IgG could interact with porcine aortic endothelial cells (PAEC). Histochemical analysis of porcine aorta sections revealed that the carbohydrate structures recognized by the anti-beta-galactose IgG are present on endothelial cells but in a cryptic form that can be unmasked by sialidase treatment. These structures were also found to be cryptic in cultured PAEC. In addition we demonstrated that PAEC may adsorb fetal calf serum (FCS) glycoproteins when cultured in FCS-supplemented medium, a process susceptible to generating artifactual observations in carbohydrate antigens analysis. In conclusion, despite their abundance, human anti-beta-galactose IgG do not represent a primary concern in pig-to-human xenotransplantation as the carbohydrate structures to which they bind are normally masked by sialic acid residues on porcine endothelial cells. However, whether these cryptic epitopes might be exposed on endothelial cells from genetically engineered animals should be further investigated because, if so, additional approaches will be needed to suppress their interaction with human anti-beta-galactose IgG.
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PMID:The target antigens of naturally occurring human anti-beta-galactose IgG are cryptic on porcine aortic endothelial cells. 1080 52

Sialidase fusion protein is reported to have great potential to combat seasonal and pandemic influenza, because it may prevent influenza virus infection by removing all sialic acid receptors from host cells. Meanwhile, recent studies have demonstrated that absence of alpha2-6 sialic acid does not protect a cell from influenza infection, and influenza virus can infect desialylated cells, suggesting that accessible surface sialic acid is dispensable for influenza virus infection. In addition, studies using animal models have shown that neuraminidase promotes adherence and invasion of Streptococcus pneumoniae, because cleavage of sialic acid from host cells exposes cryptic receptors for S. pneumoniae. The purpose of this article is to comment on the benefits and potential risks of using sialidase fusion protein as an experimental drug to combat seasonal and pandemic influenza.
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PMID:Concerns of using sialidase fusion protein as an experimental drug to combat seasonal and pandemic influenza. 1902 76


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