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)

Sialidase has been purified from rat liver cytosol 83,000-fold by sequential chromatography on DEAE-cellulose, CM-cellulose, Blue-Sepharose, Sephadex G-200, and heparin-Sepharose. When subjected to sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis, the purified cytosolic sialidase moved as a single protein band with Mr = 43,000, a value similar to that obtained by sucrose density gradient centrifugation. The purified enzyme was active toward all of the sialooligosaccharides, sialoglycoproteins, and gangliosides tested except for submaxillary mucins and GM1 and GM2 gangliosides. Those substrates possessing alpha 2----3 sialyl linkage were hydrolyzed much faster than those with alpha 2----6 or alpha 2----8 linkage. The optimum pH was 6.5 for sialyllactose and 6.0 for orosomucoid and mixed brain gangliosides. The activity toward sialyllactose was lost progressively with the progress of purification but restored by addition of proteins such as bovine serum albumin. In contrast, neither reduction by purification nor restoration by albumin was observed for the activity toward orosomucoid. When mixed gangliosides were the substrate, bile acids were required for activity and this requirement became almost absolute after the enzyme had been purified extensively. Intracellular distribution study showed that about 15% of the neutral sialidase activity was in the microsomes. The enzyme could be released by 0.5 M NaCl; the released enzyme was indistinguishable from the cytosolic sialidase in properties.
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PMID:Purification and characterization of cytosolic sialidase from rat liver. 399 46

The effects of the sequential application of specific glycosidases on surfaces of living mammalian cells were studied with respect to their ability to bind the beta-galactoside-specific lectin, Ricinus communis agglutinin (RCA). Sialidase and beta-galactosidases from different sources were tested for their actions on two strains of mouse lymphoma cells differing markedly in their metastatic potential. Binding studies were performed by quantitative flow cytometry with fluorescent RCA, and numbers of specific binding sites and equilibrium association constants for the lectin on living cells were determined before and after the various enzyme treatments. Although the number of binding sites for native and sialidase-treated cells were almost identical for both cell strains, differences in the apparent affinity constants could be detected. Differences between the two strains became even more pronounced, also with respect to the number of binding sites, after treatment with beta-galactosidases from S. pneumoniae and from bovine testis. It is suggested that such combined strategies provide valuable tools for the differentiation of surface carbohydrate moieties on intact living cells, especially for comparative purposes.
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PMID:The effect of specific glycosidases on Ricinus communis agglutinin binding to cell surfaces of two tumor sublines. A comparative flow-cytometric study. 621 Jan 45

The ability of specific gangliosides to function as host cell receptors for Sendai virus was investigated by using Madin-Darby bovine kidney cells which become resistant to infection upon treatment with Vibrio cholerae sialidase. Sialidase-treated cells were incubated for 20 min at 37 degrees C with individual, highly purified gangliosides containing homogeneous carbohydrate moieties and then inoculated with virus for 10 min. Susceptibility of the cells to infection was monitored by hemagglutination titer of the virus produced 48 hr after inoculation. Incubation of the cells with gangliosides containing the sequence NeuAc alpha 2,3Gal beta 1,3GalNAc (i.e., GD1a, GT1b, and GQ1b) fully restored susceptibility to infection to the cells. However, the ganglioside GQ1b in which the sequence ends with two sialic acids in a NeuAc alpha 2,8NeuAc linkage instead of a single sialic acid as in GD1a and GT1b, was effective as a receptor at a concentration 1/100th that of any of the other gangliosides tested. Incubation with gangliosides similar in structure to GD1a, GT1b, and GQ1b but lacking the sialic acid attached to the terminal galactose (i.e., GM1 and GD1b) had no effect. The results from control experiments in which gangliosides were incubated at 0 degrees C with cells or in which trypsin was used to remove gangliosides adsorbed to cells were consistent with the premise that the gangliosides must actually insert into the cellular membrane to function as Sendai virus receptors. Addition of 4 X 10(6) molecules of 14C-labeled GD1a per cell made the cells fully susceptible to infection. Analysis of the ganglioside content of cell membranes showed that gangliosides GD1a, GT1b, and GQ1b are natural components of these cells and are present in quantities sufficient to act as receptors. These results demonstrate that gangliosides with the proper carbohydrate sequence, such as GD1a, GT1b, and GQ1b, function as natural receptors for Sendai virus in host cells.
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PMID:Specific gangliosides function as host cell receptors for Sendai virus. 627

A sialidase (neuraminidase, acylneuraminosyl hydrolase, EC 3.2.1.18) has been discovered and isolated from Gardnerella vaginalis (ex. Haemophilus vaginalis), a possibly pathogenic inhabitant of the female genital tract. Bacteria were grown in peptone-yeast-extract medium with 2.0 mM N-acetylmannosamine as enzyme inductor under CO2 atmosphere. Sialidase activity was found in the bacterial sediment and in the culture medium. The enzyme was liberated from the cells by ultrasonic treatment. Purification was performed by 60-80% ammonium sulfate precipitation and by column chromatography on Sepharose CL-6B and Sephadex G 200. The enzyme revealed a molecular weight in the range of Mr 75 000 and a pH optimum at 5.5. Among the different types of NeuAc-containing glycoconjugates, the enzyme exhibits its highest activities towards the globular glycoproteins alpha 1-acid glycoprotein and fetuin. Taking their cleavage rate as 100, it is around 55 for II3NeuAc-Lac, 45 for bovine submaxillary mucin, 35 for II6NeuAc-Lac and IV3, III6NeuAc2-LcOse4. The rates for III8,II3NeuAc2-Lac, gangliosides and colominic acid are below 20. Due to its specificity pattern, the enzyme may play a role in the pathogenic process of G. vaginalis infections.
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PMID:A newly discovered sialidase from Gardnerella vaginalis. 633 32

We analyzed the subcellular localization of sialidases in human lymphocytes from a patient with adult type sialidosis with partial beta-galactosidase deficiency and normal controls. Sialidase activities were measured with alpha,2 leads to 3 NeuAc-lactitol, 4-methylumbelliferyl-NeuAc and GM3 ganglioside as substrates. Sialidases in the lysosomes were sonication-labile and hydrolyzed mainly hydrophilic substrates such as NeuAc-lactitol and 4-methylumbelliferyl-NeuAc, but hydrolyzed subsidiarily GM3 ganglioside. On the other hand, sialidases in the plasma membrane were sonication-stable and hydrolyzed both hydrophilic substrates and GM3 ganglioside. In sialidosis with partial beta-galactosidase deficiency, the sialidases of the lysosomes showed 3-5% activity toward hydrophilic substrates and 25% activity toward GM3 ganglioside as compared with sialidase activities of the controls. However, there are no differences in the activities of the sialidases in the plasma membrane. These results demonstrate that the essential defect in this disease is the deficiency of a lysosomal sialidase.
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PMID:Lysosomal sialidase deficiency in sialidosis with partial beta-galactosidase deficiency. 640 33

Rat kidney cortex sialidase was studied using alpha-sialyl-(2----3)-[3H]lactitol and alpha-sialyl-(2----6)-[3H]lactitol as substrates. The enzyme was found mainly in the lysosomal fraction. Only 23% of the sialidase activity of this fraction could be solubilized by a combination of freezing-thawing, sonication and Triton X-100 treatment. The optimal pH for the lysosomal enzyme activity was 4.2 and the enzyme's Km values for alpha-sialyl-(2----3)-lactitol and alpha-sialyl-(2----6)-lactitol were 0.28 and 0.41 mM, respectively. The specific activity was twice as high with the former substrate than with the latter. Sialidase activities in dialyzed kidney cortex homogenates of streptozotocin-diabetic rats and of age-matched control rats were compared. The specific activity was found to be significantly increased in the diabetic animals when using both substrates 5950 +/- 720 (S.E.) dpm/h per mg protein (n = 7) vs. 3970 +/- 370 in the controls (n = 8) with alpha-sialyl-(2----3)-lactitol (P less than 0.025) and 2870 +/- 300 vs. 1820 +/- 170 with alpha-sialyl-(2----6)-lactitol (P less than 0.02). The activities were also found to be increased when expressed per whole kidney cortex (P less than 0.005 and P less than 0.001, respectively). The elevated sialidase activity in diabetic kidney cortex may be related to the reported decrease in sialic acid content of the glomerular basement membrane, which lowers its negative charges and which may contribute to an increased permeability to proteins.
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PMID:Studies on kidney sialidase in normal and diabetic rats. 646 10

The conditions of a linear assay for 4-methylumbelliferyl-alpha-D-N-acetyl-neuraminic acid (4-MU-NeuAc) sialidase activity in human lymphocytes, granulocytes, platelets and red cells plasma membranes have been determined. Lymphocytes and granulocytes have the same pH curve with two maximums at pH 4.0 and 4.8; however lymphocytes show a higher specific activity and a higher Km value. Sialidase activity detected in red cells plasma membranes has again a double-peak pH curve with maximums at pH 4.2 and pH 4.6, and specific activity levels less than one/30 compared to the other blood cells preparations. Platelets have a sialidase activity of the same magnitude as granulocytes, with an optimum pH at 4.2.
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PMID:Human blood cells sialidases. 647 94

Sialidase activities have been studied in bovine thyroid using sialoglycolipids, sialoglycoproteins, sialo-oligosaccharides and fluorogenic 4-methylumbelliferyl-alpha-D-N-acetylneuraminate as substrates. No sialidase activity could be detected towards native glycoprotein substrates. From enzyme kinetics, effector data and more convincingly from subcellular studies it became clear that in bovine thyroid at least two sialidase activities were present, a sialyllactitol sialidase confined to the lysosomal membrane and a glycolipid sialidase residing in the plasma membrane and displaying the features of a true ectoenzyme. The lipid requirement for full enzyme activity supported the membrane bound character of both sialidase activities. A soluble sialidase activity could not be demonstrated. After solubilization by CHAPS treatment, partial purification of the sialyllactitol sialidase could be achieved by affinity chromatography (Sepharose diamino dipropylamino-N-acetylneuraminic acid). The purified enzyme was extremely labile. Titration of the sialidase preparation with amino acid modifying agents revealed that sulfhydryl- and tryptophanyl groups were essential for the sialidase action.
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PMID:Characterization, purification, and subcellular localization of bovine thyroid sialidases. 652 Jan 26

gpL115 is a lymphocyte surface component that is deficient in patients with the X-chromosome-linked immune deficiency Wiskott-Aldrich syndrome (6). The glycoprotein nature of gpL115 is demonstrated through labeling in carbohydrate moieties by [3H]NaBH4 and its synthesis by lymphocytes through labeling with [35S]methionine. Native gpL115 adheres to wheat germ lectin-Sepharose and sialidase-treated gpL115 does not adhere, indicating that native gpL115 adheres via clusters of sialic acid residues. When tested on peanut lectin, which shows specificity for the disaccharide Gal beta 1-3GalNAc, gpL115 is nonadherent and sialidase-treated gpL115 is adherent, indicating the presence of the sequence sialic acid-Gal beta 1-3GalNAc, which is characteristic for O-linked (mucin-type, acidic-type) carbohydrates. A surface glycoprotein with all the above characteristics was found on the lymphoblastoid cell line CEM. CEM cells were used as immunogen to generate the monoclonal antibody L10, an IgG1, which binds native and sialidase-treated gpL115 . Sialidase-treatment of gpL115 significantly alters its physical properties, reducing its electrophoretic mobility and changing its behavior on isoelectrofocusing. Cumulatively, these findings indicate that gpL115 , like glycophorin of erythrocytes and GPIb of platelets, is a sialoglyco protein with significant quantities of O-linked carbohydrate. On treatment with limiting sialidase concentrations, gpL115 of normal lymphocytes is transformed into a series of partially desialylated species of decreasing electrophoretic mobility. This finding resembles the situation with lymphocytes of some Wiskott-Aldrich syndrome patients. Lymphocytes of eight Wiskott-Aldrich syndrome patients were found to be deficient in 125I-labeled gpL115 . Lymphocytes from three of these patients displayed an abnormal 125I-component of apparent mol wt 135,000.
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PMID:Characterization of a human lymphocyte surface sialoglycoprotein that is defective in Wiskott-Aldrich syndrome. 654 60

A further patient with a presumed primary deficiency of sialidase N-acetylneuraminic acid hydrolase EC 3.2.1.18) is described. Clinically the patient falls into the sialidosis type 2 category of the recent classification of Lowden & O'Brien (1979), i.e. he manifests coarse facies, mental retardation and skeletal changes of dysostosis multiplex as well as myoclonus and a cherry-red spot at the macula. Sialidase activity in fibroblasts was 4% of control values using a methylumbelliferone substrate. The father of the patient was found to have 50% activity. Abnormal amounts of sialyloligosaccharides were found in the urine. The electrophoretic mobility of known glycosylated enzymes and proteins was found to be altered (more anodal than usual), but could be corrected by incubation of the cell extracts with bacterial neuraminidase. The relationship of the present patient to the Lowden & O'Brien classification is discussed.
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PMID:Sialidosis type 2 (acid neuraminidase deficiency): clinical and biochemical features of a further case. 677 97


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