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)

Gangliosides are sialo-glycosphingolipids that play important roles in the interaction of cells with their environment and are thus involved in the regulation of many cellular events. Sialic acid residues are important for the conformation of a glycomolecule, their structural stability and their functions. Although decreased brain ganglioside sialic acid has been previously reported as a result of chronic ethanol treatment in rats, no reports are available on the sialylation of specific gangliosides and/or the mechanism leading to depletion of their sialic acid residues. Therefore, in this investigation, we have examined the effects of chronic ethanol treatment on (1) incorporation of [4,5-3H]N-acetylmannosamine (ManNAc) into specific rat brain gangliosides, GD3, GD1a, GT1a, and GT1b; and (2) enzymatic activities of brain sialyltransferase and sialidase at specific subcellular levels. The experiments were done in male Wistar rats pair-fed with either ethanol or control liquid diets for a period of 8 weeks. The rats were intracerebroventricularly injected with labeled ManNAc (30 microCi/rat) and killed after 90 min. Radioactivity was determined in respective ganglioside bands separated on a thin layer chromatography system. Specific activities of sialyltransferase and sialidase were assessed using GM3 and GD3 as substrates, respectively. The results showed significant decreases of 57.7% (p < 0.001) and 68.9% (p < 0.001), respectively, in the labeled ManNAc incorporation into GD3 and GD1a fractions in rats of the ethanol group, compared with rats of the control group. No significant changes were noted in the incorporation of labeled ManNAc into GT1a or GT1b ganglioside fractions between the ethanol and control groups. Concomitantly, compared with control rats, a decrease of 18.9% (p < 0.05), 20.6% (p < 0.05), and 15.8% (p < 0.001) was found in the sialyltransferase activity, respectively, at the whole brain, and brain Golgi and synaptosomal levels. However, dramatic increases of 32.4% (p < 0.05), 105% (p < 0.001), and 150% (p < 0.001) in sialidase activity were found, respectively, at the whole brain and brain cytosol and synaptosomal fractions of rat treated chronically with ethanol. Thus, we conclude that the deleterious actions of ethanol on the sialylation of rat brain gangliosides is specific, and the reduced sialic acid label found in GD3 and GD1a in this study is mainly due to increased activity of brain sialidase. Furthermore, the study reaffirms our tenet that, regardless of whether it is the liver or the brain, glycosylation cascade is one of the main target of the deleterious attacks of ethanol.
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PMID:Long-term ethanol consumption selectively impairs ganglioside pathway in rat brain. 975 36

We previously demonstrated that transfection of a sialidase cDNA into B16-BL6 cells, a highly metastatic and invasive cell line derived from the mouse B16 melanoma, resulted in a marked suppression of metastasis accompanied by decreased cellular content of the GM3 that is one of the target molecules of the sialidase expressed (Tokuyama et al., 1997 Int. J. Cancer, 73, 410-415). To obtain further insight into the involvement of sialidase in metastasis, we made a comparison of the levels of sialidase activity and GM3 content between B16 melanoma cell lines with low (B16-F1) and high (B16-F10 and -BL6) metastatic potential. The cells exhibited sialidase activity towards 4-methylumbelliferyl N-acetylneuraminic acid (4MU-Neu5Ac) and gangliosides at acidic pH in the particulate fractions, but not in the cytosol. The activity toward 4MU-NeuAc was significantly lower in highly metastatic cells. The activity toward gangliosides, on the other hand, varied independently of metastatic potential: B16-F10 cells with a high potential for experimental metastasis showed the lowest level and B16-BL6 cells having high invasiveness had rather a higher level of ganglioside sialidase along with a much greater GM3 synthase activity than the other two cell lines. Flow cytometric analysis with anti-GM3 antibody revealed that highly metastatic cell lines were higher in the binding affinity as compared to B16-F1 cells, B16-BL6 cells containing twice as much cellular GM3 as B16-F1 cells on thin-layer chromatography.
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PMID:Comparative study of sialidase activity and G(M3) content in B16 melanoma variants with different metastatic potential. 982 65

5,9-Diacetamido-2,6-anhydro-O-4-carbamoylmethyl-3,5,9-trideo xy-D-glycero- D-galacto-non-2-enonic acid (1) was synthesized via a key intemediate 2 through the Neu5Ac aldolase [E.C.4.1.3.3]-catalyzed aldol reaction of 2-acetamido-2,6-dideoxy-6-azido-D-glucose with sodium pyruvate operating under alkaline conditions (pH 10.5) in order to accelerate epimerization C-2 of N-acetyl-D-glucosamine (D-GlcNAc) derivatives. Compound 1 showed inhibitory activity against sialidase.
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PMID:Chemoenzymatic synthesis of an N-acetylneuraminic acid analogue having a carbamoylmethyl group at C-4 as an inhibitor of sialidase from influenza virus. 986 96

Intramolecular trans-sialidase from leech (Macrobdella decora) is the first member of the sialidase superfamily found to exhibit strict specificity towards the cleavage of terminal Neu5Acalpha2-->3Gal linkage in sialoglycoconjugates. Its release of 2,7-anhydro-Neu5Ac instead of Neu5Ac indicates that it catalyzes an intramolecular trans-sialosyl reaction. Crystal structures of its complexes with an inactive substrate analogue 2-propenyl-Neu5Ac, and with the product 2,7-anhydro-Neu5Ac, have been determined to 1.8 A resolution. The boat conformation of the pyranose observed in the complexes supports the proposed enzymatic mechanism that O7 of an axial 6-glycerol group attacks the positively charged C2 of the intermediate. A generalized mechanism is proposed for the sialidase superfamily.
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PMID:The 1.8 A structures of leech intramolecular trans-sialidase complexes: evidence of its enzymatic mechanism. 987 9

Sialic acids from the liver and serum of guinea-pig are composed of N-acetylneuraminic acid (Neu5Ac; 85% and 61%, respectively), N-acetyl-4-O-acetylneuraminic acid (Neu4,5Ac2; 10% and 32%, respectively) and N-glycolylneuraminic acid (Neu5Gc; 5% and 7%, respectively), besides traces of N-glycolyl-4-O-acetylneuraminic acid in serum. The analysis was carried out using thin-layer chromatography, high-performance liquid chromatography, electron impact ionization mass spectrometry, and different enzymes (sialidase, sialate esterase, and sialate-pyruvate lyase after hydrolysis and purification of the sialic acids by ion-exchange chromatography). We showed that this O-acetylation of sialic acids is due to the activity of an acetyl-coenzyme A:sialate-4-O-acetyltransferase (EC 2.3.1.44), which occurs together with sialyltransferase activity in Golgi-enriched membrane fractions of guinea-pig liver. The enzyme operates optimally at 30 degrees C in 70 mM potassium phosphate buffer at pH 6.7 and in the presence of 90 mM KCI with an apparent KM for AcCoA of 0.6 1microM and a Vmax of 20 pmol/mg protein x min. The enzyme is inhibited by coenzyme A in a mixed-competitive manner (Ki = 4.2 microM), as well as by parachloromercuribenzoate, MnCl2, saponin and Triton X-100.
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PMID:Enzymatic 4-O-acetylation of N-acetylneuraminic acid in guinea-pig liver. 1005 93

To understand the reason why, in the absence of GM2 activator protein, the GalNAc and the NeuAc in GM2 (GalNAcbeta1-->4(NeuAcalpha2-->3)Galbeta1-->4Glcbet a1-1'Cer) are refractory to beta-hexosaminidase A and sialidase, respectively, we have recently synthesized a linkage analogue of GM2 named 6'GM2 (GalNAcbeta1-->6(NeuAcalpha2-->3)Galbeta1-->4Glcbet a1-1'Cer). While GM2 has GalNAcbeta1-->4Gal linkage, 6'-GM2 has GalNAcbeta1-->6Gal linkage (Ishida, H., Ito, Y., Tanahashi, E., Li, Y.-T., Kiso, M., and Hasegawa, A. (1997) Carbohydr. Res. 302, 223-227). We have studied the enzymatic susceptibilities of GM2 and 6'GM2, as well as that of the oligosaccharides derived from GM2, asialo-GM2 (GalNAcbeta1-->4Galbeta1--> 4Glcbeta1-1'Cer) and 6'GM2. In addition, the conformational properties of both GM2 and 6'GM2 were analyzed using NMR spectroscopy and molecular mechanics computation. In sharp contrast to GM2, the GalNAc and the Neu5Ac of 6'GM2 were readily hydrolyzed by beta-hexosaminidase A and sialidase, respectively, without GM2 activator. Among the oligosaccharides derived from GM2, asialo-GM2, and 6'GM2, only the oligosaccharide from GM2 was resistant to beta-hexosaminidase A. Conformational analyses revealed that while GM2 has a compact and rigid oligosaccharide head group, 6'GM2 has an open spatial arrangement of the sugar units, with the GalNAc and the Neu5Ac freely accessible to external interactions. These results strongly indicate that the resistance of GM2 to enzymatic hydrolysis is because of the specific rigid conformation of the GM2 oligosaccharide.
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PMID:Structural basis for the resistance of Tay-Sachs ganglioside GM2 to enzymatic degradation. 1018 78

Tritrichomonas foetus is an obligate parasite of the bovine urogenital tract producing infection associated with inflammatory changes, abortion, and infertility, Tritrichomonas mobilensis was isolated from squirrel monkey colon, and symptoms involve diarrheal complications. Both tritrichomonads produced hemagglutinins with the properties of sialic acid-specific lectins. Assays on the adherence of these protozoans to Chinese hamster ovary (CHO) cells and to bovine cervical and monkey colon mucus were performed to assess the function of the lectins in adhesion. Sialic acid at concentration as low as 2 mM inhibited the adhesion to CHO cells, less effectively to the mucus. Predigestion with Clostridium perfringens sialidase prevented the adhesion to both epithelial cells and the mucus. Inhibition of endogenous sialidases with 2,3-dehydro-2-deoxy-NeuAc increased the adhesion of T. mobilensis to CHO cells. Specific anti-T. foetus lectin (TFL) and anti-T. mobilensis lectin (TML) antibodies inhibited adhesion of the trichomonads to the epithelial cells and to the mucus. TFL histochemistry disclosed the presence of lectin ligands on keratinized vaginal epithelia, cervical mucosa, and mucin and on endometrial glands and their secretions. TML histochemistry showed reactivity with the luminal membranes of colonic glandular epithelium and less with the colonic mucin. Both lectins bound to the surface membrane of CHO cells. Anti-lectin antibodies showed granular cytoplasmic and strong membrane localization of the lectins in both tritrichomonads. Although the 2 tritrichomonads have different habitats, the results indicate that both these protozoa use lectins with sialic acid specificity for adhesion to mucosal surfaces.
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PMID:Sialic acid-specific lectin-mediated adhesion of Tritrichomonas foetus and Tritrichomonas mobilensis. 1020 60

N-Acetylneuraminic acid (Neu5Ac) was converted into the methyl ester methyl ketoside-8,9-epoxy derivative (8). Methylation of 8 followed by deprotection gave 4,7-di-O-methyl-Neu5Ac (10). Compound 10 was converted into the corresponding methyl ester-chloroacetate derivative, which was subsequently coupled to 5-bromo-indol-3-ol to give the chromogenic product (13). Deprotection of 13 gave 5-bromo-indol-3-yl 4,7-di-O-methyl-Neu5Ac (5). The product 5 was specifically cleaved by sialidase from either influenza A or influenza B virus to give an indigo-blue precipitate, but was not cleaved by several bacterial or viral sialidases tested. The properties of product 5 relative to a fluorescent substrate for sialidase were also documented.
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PMID:Synthesis of bromoindolyl 4,7-di-O-methyl-Neu5Ac: specificity toward influenza A and B viruses. 1046 15

KDN (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid), a sialic acid analog, has been found to be widely distributed in nature. Despite the structural similarity between KDN and Neu5Ac, alpha-ketosides of KDN are refractory to conventional sialidases. We found that the hepatopancreas of the oyster, Crassostrea virginica, contains two KDN-cleaving sialidases but is devoid of conventional sialidase. The major sialidase, KDN-sialidase, effectively cleaves alpha-ketosidically linked KDN and also slowly cleaves the alpha-ketosides of Neu5Ac. The minor sialidase, KDNase, is specific for alpha-ketosides of KDN. We were able to separate these two KDN-cleaving enzymes using hydrophobic interaction and cation-exchange chromatographies. The rate of hydrolysis of 4-methylumbelliferyl-alpha-KDN (MU-KDN) by KDN-sialidase is 30 times faster than that of MU-Neu5Ac in the presence of 0.2 M NaCl, whereas in the absence of NaCl this ratio is only 8. KDNase hydrolyzes MU-KDN over 500 times faster than MU-Neu5Ac and is not affected by NaCl. KDN-sialidase purified to electrophoretically homogeneous form was found to have a molecular mass of 25 kDa and an isoelectric point of 8.4. One of the three tryptic peptides derived from KDN-sialidase contains the consensus motif, SXDXGXTW, that has been found in all conventional sialidases. Kinetic analysis of the inhibition of the hydrolysis of MU-KDN and MU-Neu5Ac by 2, 3-dehydro-2-deoxy-KDN (KDN2-en) and 2,3-dehydro-2-deoxy-(Neu5Ac2-en) suggests that KDN-sialidase contains two separate active sites for the hydrolysis of KDN and Neu5Ac. Both KDN-sialidase and KDNase effectively hydrolyze KDN-G(M3), KDNalpha2-->3Gal beta1-->4Glc, KDNalpha2-->6Galbeta1-->4Glc, KDNalpha2-->6-N-acetylgalactosaminitol, KDNalpha2-->6(KDNalpha2-->3)N-acetylgalactosaminitol, and KDNalpha2-->6(GlcNAcbeta1-->3)N-acetylgalactosaminitol. However, only KDN-sialidase also slowly hydrolyzes G(M3), Neu5Acalpha2-->3Galbeta1-->4Glc, and Neu5Acalpha2-->6Galbeta1-->4Glc. These two KDN-cleaving sialidases should be useful for studying the structure and function of KDN-containing glycoconjugates.
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PMID:2-Keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN)- and N-acetylneuraminic acid-cleaving sialidase (KDN-sialidase) and KDN-cleaving hydrolase (KDNase) from the hepatopancreas of oyster, Crassostrea virginica. 1054 27

Sialidases (E.C.3.2.1.18) belong to a group of glycohydrolytic enzymes, widely distributed in nature, which remove sialic acid residues from glycoproteins and glycolipids. All of the sialidase so far characterized at the molecular level share an Asp block, repeated three to five times in the primary structure, and an F/YRIP sequence motif which is part of the active site. Using a sequence homology-based approach, we previously identified a human gene, named NEU2, mapping to chromosome 2q37. NEU2 encoded protein is a polypeptide of 380 amino acids with two Asp block consensuses and the YRIP sequence in the amino terminal part of the primary structure. Here we demonstrate that NEU2 encodes a functional sialidase. NEU2 was expressed in COS7 cells, giving rise to a dramatic increase in the sialidase activity measured in cell extracts with the artificial substrate 4-MU-NANA. Using a rabbit polyclonal antiserum, on Western blots a protein band with a molecular weight of about 42 kDa was detectable, and its cytosolic localization was demonstrated with cell fractionation experiments. These results were confirmed using immunohistochemical techniques. NEU2 expression in E.coli cells allowed purification of the recombinant protein. As already observed in the enzyme expressed in COS7 cells, NEU2 pH optimum corresponds to 5.6 and the polypeptide showed a K(m)for 4-MU-NANA of 0.07 mM. In addition, based on the detectable similarities between the NEU2 amino acid sequence and bacterial sialidases, a prediction of the three-dimensional structure of the enzyme was carried out using a protein homology modeling approach.
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PMID:Expression of a novel human sialidase encoded by the NEU2 gene. 1056 56


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