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 Tn antigen (GalNAc alpha 1-O-Ser/Thr) is a disease-related O-linked (mucin-type) carbohydrate neoantigen which is expressed in idiopathic Tn syndrome, AIDS, T-cell lymphoma and in many carcinomas. In the present study, we took advantage of a Tn antigen expressing T-lymphocyte clone derived from a patient with the idiopathic form of the Tn syndrome and the Tn+ Jurkat cell line to characterize new reagents that should identify Tn antigens (monoclonal antibody 5F4 and a lectin newly isolated from Moluccella laevis seeds). Flow cytometry revealed that both reagents strongly bound to Tn antigen expressing T lymphocytes but not to normal donor T cells, which are Tn negative. In contrast to mAb 5F4, Moluccella laevis lectin weakly bound to normal donor cells after sialidase pretreatment, indicating its broader specificity. N-Acetyl-D-galactosamine at a concentration of 100 mM significantly reduced antibody binding and abolished lectin binding, completely demonstrating the sugar specificity of both reagents. These reagents should be useful tools in glycobiology and for clinical purposes.
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PMID:Use of O-glycosylation-defective human lymphoid cell lines and flow cytometry to delineate the specificity of Moluccella laevis lectin and monoclonal antibody 5F4 for the Tn antigen (GalNAc alpha 1-O-Ser/Thr). 837 May 96

The protozoan parasite Trypanosoma cruzi must enter cells of its vertebrate host in order to replicate. Once this is accomplished, the infective trypomastigotes can invade many different cell types from several host species. This observation is in agreement with the parasite's wide natural host range. Studies performed with cultured mammalian cells in vitro have shown that T. cruzi invasion is an unusual process, distinct from phagocytosis, that depends on parasite energy and on negatively charged surface molecules of the host cell. Several surface glycoproteins and mucin-like molecules of trypomastigotes have been implicated, mainly by inhibition studies with antibodies, in interactions with host cells. Recently, several of the trypomastigote surface glycoproteins were shown to be related members of a large family that includes the T. cruzi trans-sialidase. The mucin-like molecules are beginning to emerge as a separate family of threonine-rich, O-glycosylated molecules that function as acceptors of sialic acid in the infective stages. Several lines of evidence suggest that parasite surface molecules mediate binding to host cells, whereas invasion of nonphagocytic cells involves recruitment of host-cell lysosomes, an unusual event apparently triggered by signal transduction.
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PMID:The mechanisms of Trypanosoma cruzi invasion of mammalian cells. 856 58

Clostridium perfringens produces two sialidases, one of which has a molecular mass of 71 kDa and is secreted, while the 'small', 43 kDa isoenzyme remains in the cells. The secreted, higher molecular mass sialidases of two different clostridial strains, DSM756T and A99, exhibit maximum activity at pH 5.5 and at 51 or 55 degrees C, respectively. The molecular mass of both enzymes is 71 kDa in SDS-PAGE and 63 kDa as determined by gel-filtration, which indicates the absence of subunits. Natural sialidase substrates are hydrolyzed at comparably high rates, e.g. the glycoproteins fetuin and bovine submandibular gland mucin, the homopolymer colominic acid, and the ganglioside mixture from bovine brain. The partially purified 'small' isoenzyme from C. perfringens A99 cells had similar properties to the corresponding recombinant sialidase isolated from the Escherichia coli host. It is located inside the clostridial and E. coli cells and exhibits maximum activity at pH 6.1 and 37 degrees C. A relative molecular mass of 32,000 was found with FPLC gel-filtration chromatography, while primary structure analysis yielded a value of 43,000. It differs a significantly from the 'large' isoenzyme by substrate specificity. Preferred substrates are oligosaccharides, while other, more complex sialoglycoconjugates are hydrolyzed only at very low rates. alpha 2,3-linkages are hydrolyzed much faster than alpha 2,6-bonds.
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PMID:Diversity in the properties of two sialidase isoenzymes produced by Clostridium perfringens spp. 856 16

Trypanosoma cruzi expresses a unique trans-sialidase that is responsible for the transfer of sialic acid from host glycoproteins and glycolipids to mucin-like glycoprotein acceptors on the parasite surface. The enzyme and the sialic acid acceptors are present in the mammalian forms of the parasite and in the parasite forms that grow in axenic cultures, which correspond to the developmental stages found in the insect vectors. Here we show that parasite forms growing in the vector Triatoma infestans express trans-sialidase in the hindgut portions of the insect. However, the sialic acid acceptors are poorly sialylated due to the low concentration of sialic acid donors in the gut lumen of T.infestans, which feeds exclusively on blood that is rich in sialic acid donors. These low levels of sialic acid donors are due to a novel sialidase activity present mainly in the anterior midgut with high specificity for alpha-2,3-sialyllactose, but not for alpha-2,6-sialyllactose. The activity is present in starved insects or insects fed with culture medium, indicating that it did not originate from the blood meal. Enzyme activity does not decrease in insects fed with antibiotics, is present in the salivary glands, and the few bacteria isolated from the gut and faeces of T.infestans did not display sialidase activity, indicating that the enzyme is not derived from a commensal organism. This novel activity could have a nutritional role in the gut of haematophagous insects and indicates that acquisition of sialic acid is not required for parasite development in the gut of T.infestans.
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PMID:A sialidase activity in the midgut of the insect Triatoma infestans is responsible for the low levels of sialic acid in Trypanosoma cruzi growing in the insect vector. 856 50

Nine strains of Streptococcus oralis, isolated from blood cultures of patients with infective endocarditis or from the oral cavity as part of the normal flora, were examined for their ability to elaborate sialidase (neuraminidase) and N-acetylglucosaminidase, enzymes which are involved in the degradation of glycoproteins. Both glycosidases were induced when bacteria were grown in a minimal medium supplemented with porcine gastric mucin, a model glycoprotein, and repressed when growth occurred in the presence of glucose. Cell-free extracts mucin-grown cultures expressed elevated levels of N-acetylneuraminate pyruvate-lyase (the first intracellular enzyme in the pathway of N-acetylneuraminate catabolism), N-acetylglucosamine (glcNAc)-6-phosphate deacetylase and glucosamine-6-phosphate deaminase (enzymes involved in the intracellular catabolism of GlcNAc 6-phosphate); activity of each of these intracellular enzymes was markedly repressed when bacteria were grown in media supplemented with alpha 1-acid glycoprotein, a major component of human plasma. Cells from these cultures expressed high levels of sialidase, N-acetylglucosaminidase, and the intracellular enzymes involved in the catabolism of N-acetyl-sugars released by action of these glycosidases. High-resolution 1H-NMR spectroscopy of spent culture supernatants revealed that sialic acid and GlcNAc residues of the molecularly mobile oligosaccharide side-chains of alpha 1-acid glycoprotein had been hydrolysed and the released sugars internalized by the bacteria. These data indicate that S. oralis has the ability to hydrolyse constituents of oligosaccharide side-chains of host-derived glycoproteins and to utilize simultaneously these released carbohydrates. The biochemical characteristics induced by the growth of S. oralis on glycoproteins may play a role in the survival and persistence of these bacteria at the infection site in vivo.
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PMID:Metabolism of glycoprotein-derived sialic acid and N-acetylglucosamine by Streptococcus oralis. 870 62

A hyperimmune rabbit antiserum against group C Neisseria meningitidis agglutinated and lysed Trypanosoma cruzi metacyclic trypomastigotes in a complement-mediated reaction. Immunization of rabbits with the purified polysaccharide C from N. meningitidis and of human volunteers with the AC-polysaccharide vaccine against meningitis also resulted in antibody production cross-reactive with T. cruzi infective forms. The rabbit antibodies bound to parasites, lysed metacyclic forms, and recognized several components from lysates of cell-derived trypomastigotes. The sera from six human volunteers reacted with cell-cultured trypomastigotes in vitro, lysed these forms, and recognized glycoconjugates migrating diffusely on the top of immunoblots. One serum also reacted with the isolated mucin-like glycoconjugate carrying the Ssp-3 epitope from cell-derived trypomastigotes, but treatment with sialidase did not abolish this reactivity. The anti-AC human antiserum also protected against HeLa cell infection and markedly decreased the number of parasites liberated after cell burst. The polyclonal response that resulted from human immunization with N. meningitidis polysaccharides A and C comprised trypanolytic antibodies that recognized nonsialylated epitopes expressed on infective forms of the parasite. It is suggested that human AC vaccination could be potentially helpful as an adjuvant to a specific immunotherapy of Chagas disease, developed with native or recombinant antigens of the parasite.
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PMID:Polyclonal B-cell activation by Neisseria meningitidis capsular polysaccharides elicit antibodies protective against Trypanosoma cruzi infection in vitro. 881 66

In Trypanosoma cruzi a cell surface enzyme with trans-sialidase (TS) activity has been implicated as an important factor in establishing infection. The enzyme is encoded by genes belonging to a large super-family which on the basis of sequence has been subdivided into 4 groups. TS mediates the transfer of sialic acid residues from host glycoconjugates to acceptor molecules on the parasite surface. To study the organisation of the TS genes we isolated several distinct cosmids from a library constructed with DNA from the T. cruzi X10.6 clone. In these cosmids, the TS genes (group I) were present either as single copies or as a direct tandem repeat. A common feature of the cosmids was the presence of a related group III gene located 10-12kb downstream of the TS gene(s) and arranged in the same orientation. In several of the cosmids we also identified a mucin-like glycoprotein gene located between the group I and group III genes. The mucin-like genes are part of a large polymorphic family and contour clamped homogeneous electric field electrophoresis (CHEFE) analysis showed that they were linked to members of the TS super-family at multiple sites in the X10.6 genome. Screening of a second cosmid library made with DNA from the CL-Brener clone confirmed this multiple linkage suggesting that it is a common feature of the species. This genetic organisation may have important functional significance since the mucin-like glycoproteins are the major cell surface acceptors of sialic acid.
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PMID:Mucin-like glycoprotein genes are closely linked to members of the trans-sialidase super-family at multiple sites in the Trypanosoma cruzi genome. 881 83

A new sialic acid-specific lectin from the colonic parasite of squirrel monkeys Tritrichomonas mobilensis (TML) was tested on human and mouse tissues for histochemical staining properties. There were no substantial differences in reactivity between frozen and formalin fixed paraffin sections. TML staining was blocked by preincubation with sialic acid or by sialidase digestion. TML/anti-TML antibody histochemistry was identical with the TML-gold technique. The staining pattern was not blood group dependent. TML stained strongly the luminal membranes of normal vascular endothelium as well as endothelial neoplasms. Lymphatic vessels and capillaries of kidney glomeruli and lung alveolar septi were negative or only slightly positive. In parenchymatous organs luminal membrane positivity was dominant, preferably of cells lining ducts. Weak fine-granular cytoplasmic and basolateral membrane staining was also observed. Umbrella cells in transitional epithelium and basal layers of squamous epithelia showed strong reactivity with cell membranes. Mucin in respiratory epithelium was positive whereas gastrointestinal mucins failed to stain uniformly. Erythrocytes and most white blood cell types showed distinct membrane positivity. Acetylation or alkaline O-deacetylation of tissue sections did not substantially change TML reactivity. Oxidation, however, completely blocked TML staining except for respiratory epithelium and colonic mucin.
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PMID:Histochemical localization of sialylated glycoconjugates with Tritrichomonas mobilensis lectin (TLM). 883 52

Sialidases possessing enzyme activity were solubilized from mouse-adapted influenza viruses A/PR/8/34 (A/PR8, H1N1), A/Guizhou/54/89 (A/Guizhou, H3N2) and B/Ibaraki/2/85 (B/Ibaraki) by proteolytic digestion and purified by affinity chromatography and/or sucrose density gradient centrifugation. The purified sialidases were observed as a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum pH of purified sialidases from A/PR8, A/Guizhou and B/Ibaraki against sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate were 6.5, 7.5 and 5.5, respectively. The purified sialidase (N1) from A/PR8 and its original virus showed enzyme activity with similar substrate specificity, and preferentially hydrolyzed alpha (2-->3)sialyllactose and bovine submaxillary mucin (BSM). Purified sialidase from B/Ibaraki hydrolyzed alpha (2-->3)sialyllactose, alpha (2-->6)sialyllactose and most glycoproteins, especially BSM, but the intact virus showed higher sialidase activity against sialyllactoses than against glycoproteins and gangliosides. These results indicate that the purified enzyme and the original virus of B/Ibaraki have different substrate specificities of sialidase activity. Purified A/Guizhou sialidase (N2) hydrolyzed alpha (2-->3)sialyllactose and porcine stomach mucin but not alpha (2-->6)sialyllactose and BSM. The original virus of A/Guizhou showed substrate specificity similar to its purified enzyme, except that the virus was active against BSM.
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PMID:Comparison of substrate specificities of sialidase activity between purified enzymes from influenza virus A (H1N1 and H3N2 subtypes) and B strains and their original viruses. 884 16

The 35/50 kDa mucin-like surface glycoprotein (gp35/50) of Trypanosoma cruzi metacyclic trypomastigotes has been implicated in mammalian cell invasion. In this study we investigated whether the sialyl residues of gp35/50 are required for interaction of parasites with target cells. After treatment with bacterial neuraminidase, the metacyclic forms (G strain) remained reactive with the monoclonal antibody (mAb) 10D8 but lost their reactivity with mAb 3C9, that recognizes sialic acid-containing epitopes on gp35/50, and entered HeLa cells in significantly higher numbers as compared to untreated controls. Resialylation of gp35/50, by incubation of parasites with T. cruzi trans-sialidase and sialyl lactose, restored the reactivity with mAb 3C9 as well as the affinity for sialic acid specific lectin. Accordingly, the rate of invasion of resialylated parasites was reduced to levels similar to those observed before desialylation. Purified G strain gp35/50, desialylated by neuraminidase treatment, bound to HeLa cells more than its sialylated counterpart. The Ca2+ signaling activity, which has been associated with cell invasion, was also determined by measuring the cytosolic Ca2+ concentration ([Ca2+]i), in HeLa cells upon interaction with sonicated extracts from untreated or neuraminidase-treated parasites, or with purified gp35/50 in its sialylated or desialylated form. Consistent with the results of cell invasion assay, the desialylated parasite preparations, as well as the sialic acid free gp35/50, induced an average elevation in [Ca2+]i significantly higher than that triggered by untreated controls. None of these effects, namely the increase in infectivity and Ca2+ signaling activity, was observed with neuraminidase-treated CL strain metacyclic trypomastigotes, which express a variant form of sialic acid gp35/50 molecule that is not recognized by mAb 10D8 and apparently is not involved in target cell invasion.
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PMID:Removal of sialic acid from mucin-like surface molecules of Trypanosoma cruzi metacyclic trypomastigotes enhances parasite-host cell interaction. 904 21


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