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 gene(s) encoding the Trypanosoma cruzi shed-acute-phase-antigen (SAPA) has a 5' end encoding a region containing two totally and two partially conserved Ser-X-Asp-X-Gly-X-Thr-Trp motifs which are present in bacterial neuraminidases, and a 3' end encoding tandemly repeated units of 12 amino acids. It is now reported that 54-87% of the total neuraminidase activity present in the parasite could be immunoprecipitated with polyclonal or monoclonal antibodies against the repeated amino acid units of SAPA. These immunoprecipitates also had greater than 80% of the trans-sialidase activity of the parasite. SAPA used sialyllactose, fetuin and 4-methylumbelliferyl-sialic acid as substrate donors. In the presence of a suitable acceptor molecule (lactose) the sialic acid residues were transferred to the disaccharide, whereas in the absence of acceptors the residues were transferred to water. If relatively inefficient acceptors (maltose or cellobiose) were added to the incubation mixtures, the sialic acid units were transferred both to the disaccharides and to water. It is concluded that a major T. cruzi antigen has both the trans-sialidase and the neuraminidase activities of the parasite. Both activities are probably located on the N-terminus of SAPA since antibodies directed against the C-terminus, which contains the repeated amino acid units, do not affect the enzymatic activities.
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PMID:Identification of the gene(s) coding for the trans-sialidase of Trypanosoma cruzi. 137 11

Trypomastigotes, the blood stage form of the human parasite Trypanosoma cruzi, contain an enzyme on their surface, trans-sialidase, which catalyses the transfer of sialic acid from host glycoconjugates to acceptors on its own cell surface. At least a subset of the sialic acid-bearing acceptor molecules are involved in parasite invasion of host cells, an essential step in the life cycle of the parasite. Another trypomastigote surface enzyme that affects host cell invasion is neuraminidase and recent evidence suggests that both trans-sialidase and neuraminidase activities may be expressed by the same proteins on the parasite surface. We describe here the isolation and expression of several members of a trans-sialidase--neuraminidase gene family from T.cruzi. One of the isolated genes does indeed encode a protein with both trans-sialidase and neuraminidase activities, while other members of the gene family encode closely related proteins that express neither enzymatic activity. Chimeric protein constructs combining different portions of active and inactive genes identified a region of the gene necessary for enzymatic activity. Sequence analysis of this portion of the gene revealed a limited number of amino acid differences between the predicted active and inactive gene products.
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PMID:Only some members of a gene family in Trypanosoma cruzi encode proteins that express both trans-sialidase and neuraminidase activities. 139 77

Influenza virus type C (Johannesburg/1/66) was used as a source for the enzyme O-acetylesterase (EC 3.1.1.53) with several natural sialoglycoconjugates as substrates. The resulting products were immediately employed as substrates using influenza virus type A [(Singapore/6/86) (H1N1) or Shanghai/11/87 (H3N2)] as a source for sialidase (neuraminidase, EC 3.2.1.18). A significant increase in the percentage of sialic acid released was found when the O-acetyl group was cleaved by O-acetylesterase activity from certain substrates (bovine submandibular gland mucin, rat serum glycoproteins, human saliva glycoproteins, mouse erythrocyte stroma, chick embryonic brain gangliosides and bovine brain gangliosides). A common feature of all these substrates is that they contain N-acetyl-9-O-acetylneuraminic acid residues. By contrast, no significant increase in the release of sialic acid was detected when certain other substrates could not be de-O-acetylated by the action of influenza C esterase, either because they lacked O-acetylsialic acid (human glycophorin A, alpha 1-acid glycoprotein from human serum, fetuin and porcine submandibular gland mucin) or because the 4-O-acetyl group was scarcely cleaved by the viral O-acetylesterase (equine submandibular gland mucin). The biological significance of these facts is discussed, relative to the infective capacity of influenza C virus.
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PMID:Increased influenza A virus sialidase activity with N-acetyl-9-O-acetylneuraminic acid-containing substrates resulting from influenza C virus O-acetylesterase action. 141 91

This study deals with the development of the human conjunctival goblet cells. Fifty-six eyes of human embryos and fetuses ranging from 5 to 41 weeks of gestational stage were used. The distribution of glycosaminoglycans in the goblet cells was investigated with 1% alcian blue (pH 2.5) staining. For identifying the types of glycosaminoglycans, enzyme digestion methods were carried out with streptomyces hyaluronidase, chondroitinase AC, chondroitinase ABC, or sialidase (neuraminidase). At 9 weeks of gestational age, goblet cells appeared in the fornix region of the conjunctiva and extended toward the palpebral and bulbar regions. Histochemical studies with enzyme digestion methods revealed the existence of sialomucin in the goblet cells from 9 weeks. This finding suggested that the goblet cells first appeared in the fornix area, extending toward the palpebral region, then toward the bulbar region, and containing sialomucin from their early stage of development.
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PMID:Morphological and histochemical studies of goblet cells in developing human conjunctiva. 151 64

The Salmonella typhimurium LT2 sialidase (neuraminidase, EC 3.2.1.18) structural gene, nanH, has been cloned and sialidase overproduced from multicopy plasmids in Escherichia coli. Sialidase expression was regulated positively by cAMP. In contrast, certain Tn1000 insertions located upstream of nanH coding sequences reduced sialidase activity. A nanH chromosomal insertion mutation constructed by marker exchange demonstrated a single sialidase gene copy in S. typhimurium LT2. The complete nucleotide sequence of nanH, encoding a 41,300 dalton polypeptide, was determined and the derived primary structure was similar to sialidases from Clostridium perfringens, Clostridium sordellii, Bacteroides fragilis, and Trypanosoma cruzi. Comparative sequence analysis, including codon usage and secondary structure predictions, indicated that the S. typhimurium and clostridial sialidases are homologous, strongly suggestive of an interspecies gene transfer event. At least two primary sequence motifs of the bacterial enzymes were detected in influenza A virus sialidases. The predicted secondary structure of the bacterial enzymes was strikingly similar to viral sialidase. From the population distribution of nanH detected within a collection of salmonellae, it was apparent that S. typhimurium obtained its nanH copy most recently from Salmonella arizonae. S. typhimurium LT2 is thus a genetic mosaic that differs from other strains of even the same serotype by nanH plus potentially additional characters linked to nanH. These results have relevance to the evolution and function of sialidases in pathogenic microbes, and to the origin of the sialic acids.
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PMID:Cloning, sequencing and distribution of the Salmonella typhimurium LT2 sialidase gene, nanH, provides evidence for interspecies gene transfer. 160 67

In this study, neuraminidase (sialidase) and 6 different lectins, wheat germ agglutinin (WGA), Limax flavus agglutinin (LFA), Sambucus nigra agglutinin (SNA), Maackia amurensis agglutinin (MAA), peanut agglutinin (PNA), and Amaranthin, were used to histochemically characterize the carbohydrate structure of glycoconjugate in the murine eustachian tube pharyngeal orifice. A microwave irradiation technique was used to reduce the incubation time and background staining. After neuraminidase treatment, WGA, LFA, MAA, Amaranthin, and PNA stained epithelial goblet cells, glandular mucous cells, cell surfaces, and the mucous blanket. Without neuraminidase treatment, SNA and PNA did not stain any secretory cells. These results revealed that sialoglycoconjugates in the murine eustachian tube pharyngeal orifice are produced from epithelial goblet cells and glandular mucous cells, are present on cell surfaces and within the mucous blanket, and that their terminal trisaccharide linkage appears to be the sequence Neu5Ac (alpha 2-3) Gal (beta 1-3) GalNAc.
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PMID:[Carbohydrate structure of glycoconjugate in the murine eustachian tube pharyngeal orifice]. 161 8

A procedure for the detection of low activities of sialidase (= neuraminidase) is described. Natural substrates for sialidase (human erythrocytes, fetuin or gangliosides) were coated onto the wells of microplates and incubated at 37 degrees C with the enzyme. Sialidase-induced desialylation of these natural substrates unmasks saccharides that are specifically recognized by the peanut agglutinin lectin (PNA). The use of a peroxidase-conjugated PNA (Po-PNA) allowed the binding of the lectin to the desialylated substrate to be quantified. The amount of bound Po-PNA correlated directly with the amount of sialic acid released from the substrate, and therefore with the sialidase activity. With this method, it was possible to detect sialidase activity associated with bacteria, myxoviruses and cells from higher organisms. This method may have important clinical implications as the use of ELISA allows automation and concurrent analysis of numerous samples.
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PMID:An enzyme-linked lectin assay for sialidase. 171 84

Trans-sialidase and neuraminidase activities have been detected on the surface membrane of trypomastigotes of Trypanosoma cruzi, and both have been implicated in the parasite's invasion of host cells. We show here that these enzymes are structurally related. They are recognized by two independently derived monoclonal antibodies, are anchored to the membrane by glycosylphosphatidylinositol, copurify by ion exchange, molecular sieving, and hydrophobic chromatography, have maximal activities between pH 6.5 and 7.5, and are inactivated by heating at 56 degrees C. Furthermore, the neuraminidase and trans-sialidase reactions are coupled. An increase of the concentration of acceptors of the transfer reaction decreases the amount of free sialic acid released through the neuraminidase reaction. We conclude that a single enzyme can catalyze the transfer or the hydrolysis of macromolecular-bound sialic acid. The predominant direction of the reaction will depend on the availability of appropriate oligosaccharide acceptors of sialic acid.
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PMID:Trypanosoma cruzi trans-sialidase and neuraminidase activities can be mediated by the same enzymes. 173 17

N-Acetylneuraminic, 2-deoxy-2,3-didehydro-N-acetylneuraminic acid and the beta anomer of methoxyneuraminic acid (Neu5Ac, Neu5Ac2en, MeONeu) have been used as probes for the catalytic mechanism of the activities of the outer membrane-bound haemagglutinin-neuraminidase (HN) from newcastle disease virus (NDV). Neu5Ac and Neu5Ac2en produced a competitive inhibition of the sialidase (= neuraminidase) activity, whereas MeONeu had no effect on this activity. This lack of inhibition can be explained by the free amino-acid group lacking the acetyl substituent in the MeONeu. Neu5Ac2en produced the highest inhibition. Based on the effect of the inhibitors, a reaction mechanism is suggested. On the other hand, the above mentioned inhibitors of the sialidase activity had no effect on haemagglutinating activity, suggesting different active sites for the both activities.
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PMID:On the inhibition mechanism of the sialidase activity from Newcastle disease virus. 177 91

Rimantadine-resistant and -sensitive influenza A variants were assayed for their sialidase (neuraminidase, EC 3.2.1.18) activity. The kinetic parameters determined (pH optimum, stability against different pH values, thermal stability, activity on methylumbelliferyl-alpha-D-N-acetylneuraminic acid, N-acetylneuraminyl-lactose, fetuin and bovine submandibular gland mucin as substrates, Km with the former substrate, inhibition by two competitive inhibitors, and behavior towards amantadine) revealed the same results for both variants of the virus. Thus, it can be deduced that resistance to rimantadine does not influence the sialidase activity of influenza A virus.
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PMID:Sialidase activity in rimantadine-resistant and -sensitive influenza A viruses. 210


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