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)

Dipeptidyl aminopeptidase IV was purified 350 fold from pig kidney by chromatographic procedures including affinity chromatography with conjugates of Gly-Pro linked to Sepharose 4.B. Purified enzyme existed in a dimeric form as determined by sodium dodecyl sulfate polyacrylamide-gel electrophoresis using dimethyl suberimidate (a cross-linking reagent). The molecular weight of the subunit was estimated to be 100 000 by gel filtration with 6 M guanidine hydrochloride and to be 94 000 based on analysis of N-terminal residue (dinitrophenyl-serine). The amino acid composition of the purified enzyme was also determined. The enzyme contained 18.3% of carbohydrate consisting of mannose, galactose, fucose, glucosamine and sialic acid. The enzyme desialized with sialidase was found to still possess full enzyme activity.
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PMID:Dipeptidyl aminopeptidase IV, a glycoprotein from pig kidney. 66 15

P-selectin (CD62, GMP-140, PADGEM), a Ca(2+)-dependent lectin on activated platelets and endothelium, functions as a receptor for myeloid cells by interacting with sialylated, fucosylated lactosaminoglycans. P-selectin binds to a limited number of protease-sensitive sites on myeloid cells, but the protein(s) that carry the glycans recognized by P-selectin are unknown. Blotting of neutrophil or HL-60 cell membrane extracts with [125I]P-selectin and affinity chromatography of [3H]glucosamine-labeled HL-60 cell extracts were used to identify P-selectin ligands. A major ligand was identified with an approximately 250,000 M(r) under nonreducing conditions and approximately 120,000 under reducing conditions. Binding of P-selectin to the ligand was Ca2+ dependent and was blocked by mAbs to P-selectin. Brief sialidase digestion of the ligand increased its apparent molecular weight; however, prolonged digestion abolished binding of P-selectin. Peptide:N-glycosidase F treatment reduced the apparent molecular weight of the ligand by approximately 3,000 but did not affect P-selectin binding. Western blot and immunodepletion experiments indicated that the ligand was not lamp-1, lamp-2, or L-selectin, which carry sialyl Le(x), nor was it leukosialin, a heavily sialylated glycoprotein of similar molecular weight. The preferential interaction of the ligand with P-selectin suggests that it may play a role in adhesion of myeloid cells to activated platelets and endothelial cells.
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PMID:Identification of a specific glycoprotein ligand for P-selectin (CD62) on myeloid cells. 137 49

Post-translational modification of the scrapie prion protein (PrP) is thought to account for the unusual features of this protein. Molecular cloning of a PrP cDNA identified two potential Asn-linked glycosylation sites. Both the scrapie (PrPSc) and cellular (PrPC) isoforms were susceptible to digestion by peptide N-glycosidase F (PNGase F) but resistant to endoglycosidase H as measured by migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PNGase F digestion of PrPC yielded two proteins of Mr26K and 28K; however, the 26-k species was only a minor component. In contrast, PNGase F digestion of PrPSc yielded equimolar amounts of two proteins of Mr26K and 28K. The significance of this altered stoichiometry between the 26- and 28-kDa deglycosylated forms of PrP during scrapie infection remains to be established. Both isoforms as well as PrP 27-30, which is produced by limited proteolysis of PrPSc, exhibited a reduced number of charge isomers after PNGase F digestion. The molecular weight of PrP 27-30 was reduced from 27K-30K by PNGase F digestion to 20K-22K while anhydrous hydrogen fluoride or trifluoromethanesulfonic acid treatment reduced the molecular weight to 19K-21K and 20K-22K, respectively. Denatured PrP 27-30 was radioiodinated and then assessed for its binding to lectin columns. PrP 27-30 was bound to wheat germ agglutinin (WGA) or lentil lectins and eluted with N-acetylglucosamine or alpha-methyl-mannoside, respectively. Digestion of PrP 27-30 with sialidase prevented its binding to WGA but enhanced its binding to Ricinus communis lectin. These findings argue that PrP 27-30 probably possesses Asn-linked, complex oligosaccharides with terminal sialic acids, penultimate galactoses, and fucose residues attached to the innermost N-acetyl-glucosamine. Whether differences in Asn-linked oligosaccharide structure between PrPC and PrPSc exist and are responsible for the distinct properties displayed by these two isoforms remain to be established.
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PMID:Asparagine-linked glycosylation of the scrapie and cellular prion proteins. 250 74

The adherence of Actinomyces naeslundii to human epithelial (KB) cells is mediated by the interaction of a fimbrial lectin on this oral bacterium with epithelial cell receptors exposed by sialidase. The D-galactose- and N-acetyl-D-galactosamine-reactive plant lectins from peanut and from Bauhinia purpurea inhibit this interaction. This report describes the partial purification and characterization of a 160-kilodalton (kDa) cell surface glycoprotein which is the principal receptor for these lectins. Radioiodinated lectins detected a band of 160 kDa on sialidase-treated Western blots of epithelial cell extracts but did not detect bands on nontreated filters. However, wheat germ agglutinin was reactive with the 160-kDa band on filters that were not treated with sialidase, suggesting that this lectin recognizes the sialic acid residues of this molecule. The 160-kDa component was partially purified from n-octylglucoside extracts of the epithelial cells by wheat germ agglutinin affinity chromatography. This molecule was metabolically labeled with D-[14C]glucosamine and labeled at the cell surface by lactoperoxidase-catalyzed iodination or periodate oxidation followed by sodium borotritide reduction. Incubation of epithelial cells with sialidase before extraction resulted in the loss of the 160-kDa band and the appearance of a band at 200 kDa which was directly reactive with 125I-labeled peanut agglutinin. These results indicate that the 160-kDa glycoprotein on the surface of the epithelial cell serves as a receptor for the agglutinins from the peanut and B. purpurea and presumably the fimbrial lectin of actinomyces.
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PMID:A 160-kilodalton epithelial cell surface glycoprotein recognized by plant lectins that inhibit the adherence of Actinomyces naeslundii. 287 66

Microfilament-associated proteins and membrane-microfilament interactions are being investigated in microvilli isolated from 13,762 rat mammary ascites tumor cells. "Phalloidin shift" analyses on velocity sedimentation gradients of Triton X-100 extracts of [3H]-glucosamine-labeled microvilli identified a 120-kDa cell-surface glycoprotein associated with the microvillar microfilament core. The identification was verified by concanavalin A (Con A) blots of one- and two-dimensional (2D) electrophoresis gels of sedimented microfilament cores. By 2D-electrophoresis and lectin analyses the 120-kDa protein appeared to be a fraction of ASGP-2, the major Con A-binding glycoprotein of the sialomucin complex of the 13,762 cells. This identity was confirmed by immunoblot analyses using immunoblot-purified anti-ASGP-2 from anti-membrane serum prepared against microvillar membranes. Proteolysis of the microvilli with subtilisin or trypsin resulted in an increase in the amount of ASGP-2 associated with the microfilament cores. An increase was also observed with sialidase treatment of the microvilli, suggesting that negative charges, probably present on the highly sialated sialomucin ASGP-1 of the ASGP-1/ASGP-2 sialomucin complex, reduce ASGP-2 association with the microfilament core. Proteolysis of isolated microvillar membranes, which contain actin but not microfilaments, also increased the association of ASGP-2 with a Triton-insoluble, actin-containing membrane fraction. Purified ASGP-2 does not bind to microfilaments in sedimentation assays. Since the Triton-insoluble membrane residue is enriched in an actin-containing transmembrane complex, which contains a different glycoprotein, we suggest that the ASGP-2 is binding indirectly via this complex to the microfilament core in the intact microvilli.
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PMID:Microfilament association of ASGP-2, the concanavalin A-binding glycoprotein of the cell-surface sialomucin complex of 13,762 rat mammary ascites tumor cells. 304 20

The carbohydrate structures of two membrane glycoproteins (HANA protein and F protein) of HVJ have been determined on materials purified from virions grown in the allantoic sac of embryonated chicken eggs. Both glycoproteins contain fucose, mannose, galactose, and glucosamine but not galactosamine, indicating that their sugar chains are exclusively of the asparagine-linked type. The radioactive oligosaccharide fractions obtained from the two glycoproteins by hydrazinolysis followed by NaB[3H]4 reduction gave quite distinct fractionation patterns after paper electrophoresis. More than 75% of the oligosaccharides from F protein were acidic and separated into at least four components by paper electrophoresis. Only 18% of the oligosaccharide from HANA protein was an acidic single component. These acidic oligosaccharides could not be converted to neutral oligosaccharides by sialidase digestion. Structural studies of the neutral oligosaccharide fractions from HANA and F proteins revealed that both of them are mixtures of a series of high mannose type oligosaccharides and of complex type oligosaccharides with Gal beta 1 leads to (Fuc alpha 1 leads to 3) GlcNAc group in their outer chain moieties.
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PMID:Carbohydrate structures of HVJ (Sendai virus) glycoproteins. 626 75

Fetal cerebral neurons at the initiation of active neurite outgrowth in culture incorporate 4-fold more [3H]glucosamine into glycoproteins than into the cellular lipid fraction. After 8 days or longer, when a well-developed fiber network is apparent, lipids are labeled more extensively than the glycoproteins. Labeling of the latter is inhibited 95% and 89% by 0.5 microgram of tunicamycin per ml added to 1-day-old and 8-day-old cultures, respectively. Labeling of glycolipids is inhibited 30% in 1-day-old and 86% in 8-day-old cultures. Tunicamycin blocks incorporation of glucosamine label into practically all ganglioside species except for a resorcinol-positive, sialidase-sensitive band tentatively identified as GQ1b tetrasialoganglioside (Svennerholm ganglioside nomenclature). It also substantially reduces binding of 125I-labeled tetanus toxin to intact cells. There is 14% and 27% reduction in the total ganglioside sialic acid content in 1-day-old and 8-day-old cells treated for 24 hr with 0.5 microgram of tunicamycin per ml, but no substantial compositional changes are encountered. Tunicamycin blocks neurite outgrowth when added to cells soon after plating but causes no retraction or losses of fibers once the fiber network is established. Therefore, inhibition of neurite outgrowth by tunicamycin is not due to an effect on cellular gangliosides but can be correlated to an inhibition of protein glycosylation.
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PMID:Tunicamycin blocks neuritogenesis and glucosamine labeling of gangliosides in developing cerebral neuron cultures. 659 80

Both neutrophils and eosinophils have been shown to bind to the inducible endothelial cell adhesion molecule E-selectin. For neutrophils, one of the reported ligands for E-selectin is the sialylated Lewis X Ag (sLe(x)). To analyze the counterligands on eosinophils for E-selectin, adhesion assays were performed in which purified leukocytes were allowed to adhere to a soluble recombinant form of the molecule immobilized on plastic plates. Eosinophils, like neutrophils, bound to immobilized E-selectin, but significantly more neutrophils than eosinophils adhered in this assay. Consistent with the greater ability of neutrophils to bind E-selectin was the observation by flow cytometry that neutrophils expressed significant levels of sLe(x) and a sialylated dimeric form of the Le(x) Ag (sialyl-dimeric Le(x), or sialyl-stage-specific embryonic Ag-1, recognized by mAb FH6), whereas the expression of these epitopes on eosinophils was extremely low or undetectable. Expression was similar on eosinophils from allergic and nonallergic donors, and was not altered on eosinophils after induction of L-selectin shedding in vitro by treatment with platelet-activating factor. For both eosinophils and neutrophils, treatment with sialidase was associated with the complete elimination of sLe(x) and sialyl-dimeric Le(x) surface expression, and abolished leukocyte adhesion to E-selectin. Another glycosidase, endo-beta-galactosidase, which specifically cleaves the beta 1-4 galactose linkage to N-acetyl-glucosamine when it exists in an extended chain form such as that found in sialyl-dimeric Le(x), significantly inhibited eosinophil and neutrophil adhesion and expression of sialyl-dimeric Le(x). Such treatment also reduced sLe(x) expression on eosinophils, while having little effect on total neutrophil sLe(x) expression. For both eosinophils and neutrophils the sialylated ligand did not appear to be a glycoprotein because pretreatment of leukocytes with several proteases had no effect on adhesion to E-selectin or on expression of sLe(x) and sialyl-dimeric Le(x). These data suggest that eosinophils, like neutrophils, use sialylated, protease-resistant structures to bind to E-selectin, although the eosinophil expresses much lower levels of these structures on its surface. A major proportion of the sLe(x)-containing E-selectin ligand on the surface of eosinophils appears to be in the form of sialyl-dimeric Le(x), whereas this represents a minor proportion on the surface of neutrophils. Based on results using endo-beta-galactosidase, it appears that these cells may rely disproportionately upon the cell surface sialyl-dimeric Le(x) to bind to E-selectin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Differences between human eosinophils and neutrophils in the function and expression of sialic acid-containing counterligands for E-selectin. 750 34

This study deals with the acid phosphatase (AcPase) of the Kurloff body (KB), a large (10 microns diameter) periodic acid-Schiff-positive lysosomal inclusion body present in Kurloff cells (KC). KC AcPase were extracted, with similar yields, either with non-ionic detergent solution or after Dounce homogenization in low ionic strength buffer suggesting that they mainly correspond to hydrosoluble AcPase. After DEAE-cellulose chromatography of such crude Dounce-extracts, 97% of KC AcPase activity was recovered in the unbound glycoprotein fraction (peak I)1). The main protein content consisted of, as testified by SDS-PAGE analysis, major KC glycoproteins of 30-35 kDa. Thus, KC AcPase, and particularly sialoAcPase, may be assumed to correspond to these N-glycosylproteins among which the presence of alpha (2,6) sialoglycoproteins was previously established. Following electrophoresis on a 4-15% gradient native polyacrylamide gel or isoelectric focusing, the two size populations (200 kDa and 500 kDa) and up to 20 isoforms of KC AcPase were respectively detected by zymography in peak I. After Clostridium-derived sialidase digestion of peak I, the highly active bands observed at pH 3.5-5.2 disappeared. These zymographic patterns were similar to those obtained with crude extracts. After Concanavalin A (ConA)-Sepharose chromatography of peak I, the single ConA-bound glucosamine-labelled peak, eluted at 200 methyl-alpha-D-mannopyranose, contained the AcPase activity while the ConA-unbound peak was devoid of any acid phosphatase activity. After SDS-PAGE analysis, the ConA-bound fraction appeared to correspond only to a single broad protein band in the 30-35 kDa zone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Relationship between the acid phosphatases of the Kurloff body and the major 30-35 kDa glycoproteins of the Kurloff cell. 754 9

Lectin-carbohydrate recognition between the selectins and their ligands are among the earliest events in leukocyte recirculation, leukocyte recruitment into inflamed areas, and abnormal egress of leukocytes in diseases. Previously, we have described a dimeric sialoglycoprotein from myeloid cells with subunits of molecular mass = 120 kDa, which is selectively recognized by P-selectin (Moore, K.L., Stults, N.L., Diaz, S., Smith, D.F., Cummings, R.D., Varki, A., and McEver, R.P. (1992) J. Cell Biol. 188, 445-456). Here, we demonstrate that this P-selectin ligand carries alpha 2-3-linked sialic acids and the sialyl-Lewisx (SLex) tetrasaccharide motif. This glycoprotein contains < 1% of the total membrane-bound sialic acids and a very small fraction of the total SLex on neutrophil membranes. In spite of a relative resistance to sialidase digestion, the predominant form of sialic acid on the ligand is N-acetylneuraminic acid. Selective periodate oxidation of the side chain of sialic acids does not affect P-selectin binding and allows the introduction of tritium label into the truncated sialic acids. beta-Elimination with alkaline borohydride releases labeled O-linked oligosaccharides both from the labeled neutrophil ligand and from the ligand purified from HL-60 cells metabolically labeled with [3H]glucosamine. The ligand from both neutrophils and HL-60 cells is also susceptible to cleavage by the enzyme O-sialoglycoprotease from Pasteurella hemolytica. Analysis of the specificity of this enzyme suggests that the P-selectin ligand carries large numbers of closely spaced sialylated O-linked oligosaccharides. O-Sialoglycoprotease abolishes both direct binding of P-selectin to HL-60 cells and the adhesion of HL-60 cells to immobilized P-selectin, without significantly decreasing overall cell surface SLex expression. This indicates that the 120-kDa ligand may be the major determinant of P-selectin:myeloid cell interaction in vivo. Finally, based on the current and previous data, we hypothesize that the high affinity recognition site(s) of this P-selectin ligand may be derived from a "clustered saccharide patch" of sialylated fucosylated O-linked oligosaccharide sequences.
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PMID:Characterization of a specific ligand for P-selectin on myeloid cells. A minor glycoprotein with sialylated O-linked oligosaccharides. 768 50


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