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)

Sialoglycoconjugates were investigated in the bovine sublingual gland by direct visualization of sialic acid with specific lectins (LPA, SNA) and by histochemical procedures combined with sialidase digestion and lectins. The most reactive histological structures were found to be acini which contained glycoconjugates with terminal disaccharides consisting of sialic acid linked to galactose or N-acetylgalactosamine. Resistance to periodate oxidation was interpreted as demonstrating a relevant presence of C7, C8 and C9 acetylated sialic acids. KOH-Sialidase-DBA and KOH-Alcian blue sequences allowed the identification of C4 acetylated sialic acids.
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PMID:Variety of sialic acids occurring in the bovine sublingual gland. 789 45

Exoglycosidases remove peripheral monosaccharides from oligosaccharides and hence are capable of altering respiratory epithelial cell surface carbohydrates. We obtained saliva and tracheal secretions from 34 critically ill patients and saliva from 23 healthy subjects. Compared with the normal subjects, the ill patients had large amounts of mannosidase, fucosidase, hexosaminidase, and sialidase activity. Sialidase increased adherence of several gram-negative bacteria to epithelial cell monolayers and pure glycoproteins. Pretreatment of glycoproteins with some of the patients' saliva samples also increased bacterial adherence to the glycoproteins. We conclude that respiratory tract exoglycosidase activity increases during critical illness. By altering normal cell surface carbohydrates, exoglycosidases may facilitate bacterial adherence and respiratory tract colonization.
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PMID:Increased salivary exoglycosidase activity during critical illness. 802 47

Sialidase L releases 2,7-anhydro-NeuAc from sialoglycoconjugates (Li, Y.-T., Nakagawa, H., Ross, S. A., Hansson, G., and Li, S.-C. (1990) J. Biol. Chem. 265, 21629-21633). This enzyme has been purified more than 10,000-fold from Macrobdella leech. The final preparation gives a single protein band on SDS-polyacrylamide gel electrophoresis with the molecular mass of 84 kDa. The pI is determined to be 6.0 using isoelectric focusing. With 4-methylumbelliferyl-alpha-NeuAc as substrate, the pH optimum is between pH 5.5-7.0. Unlike regular sialidases, sialidase L is not inhibited by 2-deoxy-2,3-dehydro-NeuAc. Two of the seven tryptic peptides derived from sialidase L contain the consensus repeat S-X-D-X-G-X-T-W that has been found in the regular sialidases. Among various sialoglycoconjugates tested, sialidase L cleaves only the NeuAc alpha 2-->3Gal linkage. NeuAc alpha 2-->6Gal, NeuAc alpha 2-->6GalNAc, NeuAc alpha 2-->6GlcNAc, NeuAc alpha 2-->8-NeuAc, and NeuAc alpha 2-->9NeuAc linkages are not hydrolyzed. At pH 7.0, sialidase L and Clostridial sialidase release 46 and 92% of sialic acid, respectively, from bovine fetuin, indicating that sialidase L selectively cleaves NeuAc alpha 2-->3Gal linkages in fetuin. Sialidase L is the first sialidase found to exhibit a strict specificity toward the hydrolysis of the NeuAc alpha 2-->3Gal linkage, and it should become useful for the selective cleavage of NeuAc alpha 2-->3Gal linkages in sialoglycoconjugates without destroying other sialosyl linkages.
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PMID:Purification and characterization of sialidase L, a NeuAc alpha 2-->3Gal-specific sialidase. 803 34

Sialidase from influenza virus A (Tokyo/3/67, N2) is inhibited in slow-binding fashion by 2,3-didehydro-2,4-dideoxy-4-guanidino-N-acetyl-D-neuraminic acid. The Ki observed for the tightly-bound form at steady-state is 3 x 10(-11) M. Slow-binding, which is a consequence of the guanidinyl moiety of the inhibitor, is observed only for influenza virus A sialidase and not for influenza virus B or any other viral, bacterial, or mammalian sialidase investigated. The different results obtained for sialidases from influenza virus A and B, whose active sites are conserved, point to the involvement of the expulsion of a structural water molecule in the slow-binding mechanism.
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PMID:Slow-binding inhibition of sialidase from influenza virus. 806 34

trans-Sialidase isolated from trypomastigote forms of Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, is multimeric and heterogeneous in size. We show here that limited proteolysis of tans-sialidase with papain yields a single monomeric polypeptide chain of 70 kDa that conserves full enzymatic activity on soluble and membrane-bound substrates. The papain fragment lacks most of the 12-amino acid repeats of the carboxyl-terminal domain that comprises about 50% of the native trans-sialidase. When injected into rabbits, the papain-generated fragment induces antibodies that inhibit trans-sialidase activity and trypomastigote sialylation. The repeats are also not required for the stability of the enzyme or for the correct folding during the biosynthesis in Escherichia coli, but seem essential for trans-sialidase oligomerization. We conclude that trans-sialidase is composed of two structurally and functionally independent domains.
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PMID:A proteolytic fragment of Trypanosoma cruzi trans-sialidase lacking the carboxyl-terminal domain is active, monomeric, and generates antibodies that inhibit enzymatic activity. 813 17

Sialidase activities of rabbit blood cells and serum were measured. The leucocyte particulate fraction showed the highest specific activity of sialidase towards mixed gangliosides and sialyllactose, and the cytosolic fraction showed for fetuin. Predominant sialidase activity in the blood was detected in erythrocyte particulate fraction when mixed gangliosides were used as substrate. The sialidase for ganglioside was solubilized from the erythrocyte ghosts by using Triton X-100. The solubilized sialidase was purified 1886-fold by sequential chromatographies on DEAE-cellulose, EAH-Sepharose 4B, Octyl-Sepharose CL-4B, Sephadex G-100, concanavalin-A--Sepharose, N-(p-aminophenyl)oxamic acid-agarose and Heparin-Sepharose CL-6B. The optimum pH of purified sialidase was 4.5 for ganglioside mixture, and this enzyme exhibited M(r) = 48,000 by gel filtration. When the purified sialidase was subjected to SDS/PAGE, a major sialidase-active protein band at M(r) = 54,000 and another fainter inactive protein band with M(r) = 115,000 were observed. The purified enzyme was active towards oligosaccharides, gangliosides, fetuin glycopeptide and 4-methylumbelliferyl alpha-D-N-acetylneuraminic acid except for glycoproteins tested. Fe2+, Fe3+ and dithiothreitol significantly inhibited the enzyme activity, while Triton X-100 activated the enzyme. Inside-out vesicles and unsealed ghosts of rabbit erythrocyte showed the sialidase activity for mixed gangliosides but not for resealed ghosts or intact erythrocytes. These results indicate that the active site of this sialidase is oriented mainly on the inside of the erythrocyte membrane and not on the outside. Treatment of rabbit erythrocyte unsealed ghosts with phosphatidylinositol-specific phospholipase C liberated no sialidase activity toward mixed gangliosides from the ghosts.
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PMID:Sialidase in rabbit blood. Characterization of sialidase purified from rabbit erythrocyte membrane. 817 46

Sialidase activity in normal faecal extracts showed a preference for mucin-related glycoprotein and oligosaccharide substrates, but the presence of two or more O-acetyl esters at positions C7-C9 on the sialic acids retarded the rate of hydrolysis. A specific sialate O-acetyl esterase was detected with a lower total activity relative to sialidase with mucin substrates and having a pH optimum of 7.8 and a KM of approximately 1 mM sialate O-acetyl ester. A specific glycosulfatase activity was found in faecal extracts using the substrate lactit-[3H]ol 6-O-sulfate with a pH optimum of pH 5.0 and a KM of approximately 1 mM. Faecal extracts from ulcerative colitis (UC) patients had higher sialate O-acetyl esterase and glycosulfatase activity, while mucin sialidase activity was unchanged. Metabolically labelled mucin isolated from UC patients contained less sulfate and had lower sialic acid O-acetylation compared with normal mucin. Colonic mucin was degraded more efficiently by faecal extracts from UC patients compared with normal extracts. The UC mucin was degraded more rapidly than the normal mucin by faecal enzyme extracts from both normal and UC subjects.
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PMID:The roles of enteric bacterial sialidase, sialate O-acetyl esterase and glycosulfatase in the degradation of human colonic mucin. 835 29

Sialidase L is a NeuAcalpha2-->3Gal linkage-specific sialidase that releases 2,7-anhydro-NeuAc instead of NeuAc from sialoglycoconjugates (Chou, M.-Y., Li, S.-C., Kiso, M., Hasegawa, A., and Li, Y.-T.(1994) J. Biol. Chem. 269, 18821-18826). A 2. 5-kilobase cDNA of sialidase L was cloned by a combination of methods based on polymerase chain reactions. The composite cDNA sequence reveals an open reading frame coding for 762 amino acids, including a putative 28-residue signal peptide at the N terminus that is similar to the signal sequence of the Clostridium septicum sialidase. The result suggests that sialidase L is a secretory enzyme. The coding sequence excluding the putative signal peptide of sialidase L was overexpressed in Escherichia coli. The purified recombinant enzyme was characterized to be as active as the enzyme isolated from the leech. It also possessed the strict NeuAcalpha2-->3Gal linkage specificity and released the unique cleavage product, 2,7-anhydro-NeuAc from sialoglycoconjugates. The deduced amino acid sequence of sialidase L exhibits little similarity with other reported sialidases. However, sialidase L contains a conserved "FRIP region" and four repeating "Asp box" motifs that align well with the corresponding positions of bacterial sialidases. The predicted beta-strand structures near the conserved motifs of sialidase L are similar to those of Salmonella typhimurium sialidase. Several conserved single amino acid residues of bacterial sialidases, including those known to be involved in the active site of Salmonella enzyme, are conserved in the deduced amino acid sequence of sialidase L. This observation suggests that part of the catalytic mechanism of sialidase L may be similar to the ordinary sialidase.
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PMID:Cloning and expression of sialidase L, a NeuAcalpha2-->3Gal-specific sialidase from the leech, Macrobdella decora. 870 1

Gangliosides of the plasma membrane are important modulators of cellular functions. Previous work from our laboratory had suggested that a plasma membrane sialidase was involved in growth control and differentiation in cultured human neuroblastoma cells (SK-N-MC), but its substrates had remained obscure. We now performed sialidase specificity studies in subcellular fractions and found ganglioside GM3 desialylating activity in presence of Triton X-100 to be associated with the plasma membrane, but absent in lysosomes. This Triton-activated plasma membrane enzyme desialylated also gangliosides GD1a, GD1b, and GT1b, thereby forming GM1; cleavage of GM1 and GM2, however, was not observed. Sialidase activity towards the glycoprotein fetuin with modified C-7 sialic acids and towards 4-methylumbelliferyl neuraminate was solely found in lysosomal, but not in plasma membrane fractions. The role of the plasma membrane sialidase in gangliosides desialylation of living cells was examined by following the fate of [3H]galactose-labelled individual gangliosides in pulse-chase experiments in absence and presence of the extracellular sialidase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid. When the plasma membrane sialidase was inhibited, radioactivity of all gangliosides chased at the same rate. In the absence of inhibitor, GM3, GD1a, GD1b, GD2, GD3 and GT1b were degraded at a considerably faster rate in confluent cultures, whereas the GM1-pool seemed to be filled by the desialylation of higher gangliosides. The results thus suggest that the plasma membrane sialidase causes selective ganglioside desialylation, and that such surface glycolipid modification triggers growth control and differentiation in human neuroblastoma cells.
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PMID:Selective ganglioside desialylation in the plasma membrane of human neuroblastoma cells. 872 44

Human colon sialidase has been characterized, and its activity levels in normal mucosa and colonic adenocarcinoma have been determined. Sialidase activity was maximal at pH 5.5, and was unstable with storage at 4 and -20 degrees C. The bulk of activity was pellet-associated, and could not be released with triton X-100 or 3-([3-cholamidopropyl]- dimethylammonio)-1-propanesulfonate. Using 2'-(4-methylumbelliferyl)alpha-D-N-acetylneuraminic acid as substrate, the Km and Vmax values were estimated to be 0.140 mmol/l and 63 mU/g, respectively. Furthermore, an inhibition by substrate concentrations above 1.5 mmol/l was detected. Neuraminic acid caused a competitive inhibition with a Ki of 3.5 mmol/l. A statistically significant increase (p < 0.001) in the sialidase specific activity was found in primary colonic adenocarcinoma (104.20 +/- 8.00 mU/g) compared to that of the normal mucosa (72.50 +/- 7.67 mU/g).
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PMID:Human colon sialidase: characterization and activity levels in normal mucosa and colonic adenocarcinoma. 879 73


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