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:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The growth of diploid human fibroblasts has previously been shown to be regulated mainly by the extent of cell-cell contacts [R. J. Wieser and F. Oesch (1986) J. Cell Biol. 103, 361], these contacts being effective only when terminal, beta-glycosidically linked galactose residues were present on plasma membrane glycoproteins. These studies, in which a high cell density in sparse cell cultures has been mimicked by the addition of immobilized plasma membrane glycoproteins, have been further extended to investigate the role of terminal galactose residues directly in cell cultures. The studies presented herein show that (i) culturing human fibroblasts in the presence of beta-galactosidase resulted in an approximately twofold higher saturation density, as well as a twofold higher proliferation rate at high cell densities when compared to the rates found in control cultures. (ii) The presence of alpha-lactalbumin in the culture medium, which acts as a modifier of the activity of galactosyltransferase, had the same effect as beta-galactosidase. (iii) Addition of the lectin I from Bandeiraea simplicifolia (BS I), which is specific for terminal galactose residues, resulted in an increase in the proliferation rate of cell cultures at high cell densities, while the proliferation was not affected at low cell densities. These data show that the presence of terminal, beta-glycosidically linked galactose is vital for the efficient growth control of normal cells.
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PMID:Contact-dependent regulation of growth of diploid human fibroblasts is dependent upon the presence of terminal galactose residues on plasma membrane glycoproteins. 313 Nov 53

We investigated the structure of glycoconjugates contained within the secretory end-pieces and ductal segments in the rabbit submandibular and sublingual glands. Glycosidic sequences were examined by means of enzymatic degradation with specific glycosidases (sialidase, alpha-fucosidase, beta-galactosidase, alpha-mannosidase) followed by lectin binding with PNL-HRP, WPL-HRP, WGL-HRP, SBL-HRP, Con A-HRP. It was found that this procedure represents a valid tool for studying carbohydrates, in so far as their characterization and localization were based only on colour reactions. In particular, this research showed that sialic acid was present in the terminal dimers sialic acid-beta-galactose and sialic acid-N-acetyl-D-galactosamine within the submandibular gland, whereas in the sublingual gland it was only present as the sequence sialic acid-beta-galactose. Conversely, fucose had as the subterminal sugar N-acetyl-D-glucosamine in both glands. Also, elucidations about structural sequences concerning other non-terminal sugars were obtained.
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PMID:Visualization of carbohydrate chains in rabbit salivary glands by means of enzymatic degradation and plant lectins. 314 37

Two monoclonal antibodies, HH8 and HH9, have been established after immunization of mice with galactosyl-A glycolipid antigen having the terminal structure, Gal beta 1----3GalNAc alpha 1----3[Fuc alpha 1----2]Gal beta 1----R, which is the precursor for type 3 chain A (repetitive A) and type 3 chain H (A-associated H). Both antibodies react strongly and specifically with galactosyl-A, but HH8 (IgM) showed strong hemagglutination of blood group A1, A2, O and B erythrocytes after sialidase treatment, while HH9 (IgG1) did not react with human erythrocytes even after sialidase treatment. HH8 and anti-T antibody, but not HH9, reacted with glycophorin A after sialidase treatment. The reactivity of HH8 with glycophorin A was abolished by beta-galactosidase and was inhibited by liposomes containing galactosyl-A, but not other glycolipids. In addition, anti-T antibody and peanut lectin reacted specifically with galactosyl-A glycolipids. These findings indicate that HH8 recognizes the terminal disaccharide Gal beta 1----3GalNAc alpha 1----R, which is the same sequence as the classically known Thomsen-Friedenreich antigen (T-antigen), whereas HH9 does not cross-react with T-antigen but recognizes the entire galactosyl-A structure. The T-antigen was also demonstrated by immunohistology with HH8 after neuraminidase treatment in a subset of cells in stratified epithelium.
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PMID:Monoclonal antibodies directed to the blood group A associated structure, galactosyl-A: specificity and relation to the Thomsen-Friedenreich antigen. 328 40

Affinity-purified antibodies directed against carbohydrate-binding protein 35 (CBP35), a galactose-specific lectin, were used to screen a lambda gt 11 expression library derived from mRNA of 3T3 fibroblasts. This screening yielded several putative clones containing cDNA for CBP35, one of which was characterized in terms of its expression of a fusion protein containing beta-galactosidase and CBP35 sequences. Limited proteolysis of lysates containing the fusion protein, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with anti-CBP35, yielded a peptide mapping pattern comparable to that obtained from parallel treatment of authentic CBP35. Such a limited proteolysis followed by affinity chromatography on a Sepharose column coupled with galactose also yielded a 30-kDa polypeptide that exhibited carbohydrate-binding activity. This polypeptide can be immunoblotted with anti-CBP35, but not with antibodies directed against beta-galactosidase. These results indicate that we have identified a cDNA clone for CBP35 that yields a recombinant polypeptide with lectin activity produced in Escherichia coli. Using this cDNA clone as a probe, Northern-blot analysis showed an increased expression of the CBP35 gene when quiescent 3T3 cells were activated by the addition of serum growth factors.
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PMID:Carbohydrate-binding protein 35: molecular cloning and expression of a recombinant polypeptide with lectin activity in Escherichia coli. 332 49

Ram sperm, isolated from the caput, corpus, and cauda epididymidis, plus ejaculated cells were washed free of loosely bound components and tested for their ability to bind fluorescein-conjugated lectins (Con A, SBA, RCA, PNA, ECA and WGA) as assessed by epiluminescent-fluorescence light microscopy and flow cytometry. Detailed preliminary studies established an appropriate lectin-to-sperm ratio and incubation conditions for quantitative comparisons of sperm cell types and permitted a detailed analysis of both the amount of lectin bound as well as its distribution on the various aspects of the cell surface. Con A (mannose positive) bound weakly over the entire surface, with little change associated with maturation in the male tract. SBA (N-acetylgalactosamine positive) bound moderately strongly to caput sperm, with an emphasis on the apical ridge portion of the cell; during epididymal transit this binding was greatly diminished and was regained upon ejaculation. RCA, PNA, and ECA (galactose positive) gave generally equivalent results, where initially strong binding to the entire sperm surface decreased (over all parts of the surface except the anterior head) during epididymal maturation, with no change associated with ejaculation. WGA (sialic acid positive) binding initially was weak, but increased with epididymal transit and ejaculation. In vitro incubations with beta-galactosidase and neuraminidase confirmed the assignments given above. These data, when coupled with previous reports describing the heterogeneous distribution of proteins and lipids and changes in their distribution associated with epididymal maturation, serve to quantitatively describe changes in those aspects of the cell surface that are probably responsible for the acquisition of the capacity of the sperm to bind successfully to the oocyte.
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PMID:Changes in lectin-binding features of ram sperm surfaces associated with epididymal maturation and ejaculation. 337 79

We have investigated cell-cell and cell-substratum adhesion of Xenopus laevis neural crest cells at various stages of melanophore differentiation. Single-cell suspensions were obtained by trypsinization and aggregated in a cell-cell adhesion assay. Unpigmented cells did not adhere while the rate of adhesion of melanophores correlated with the degree of melanization. Melanophore cell-cell adhesion decreased significantly in the presence of beta-galactosidase, which suggests that cell-surface galactose is involved. Beta-galactoside-binding lectin has been isolated and purified from embryos at the stage of neural crest migration. When added to aggregating cells smaller, looser clusters formed compared to controls. When lectin was added to cells in stationary culture to test cell-substratum adhesion, melanophores spread more smoothly and formed more regular spacing patterns. These results suggest that this lectin can modulate receptors used in cell-cell and cell-substratum adhesion of melanophores.
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PMID:Studies on cellular adhesion of Xenopus laevis melanophores: modulation of cell-cell and cell-substratum adhesion in vitro by endogenous Xenopus galactoside-binding lectin. 350 76

We recently reported marked differences in insulin binding properties in Chinese hamster ovarian cell mutants with genetic defects in protein N-glycosylation. To further characterize the role of insulin receptor carbohydrates, we have now studied the effect of lectins on [125I]insulin binding to wild type (WT) Chinese hamster ovarian cells and to two mutant cell lines: B4-2-1, to which insulin was previously shown to bind with higher affinity than normal, and Lec 1, to which insulin binds with much lower affinity. The results show that of four lectins that bound to WT cells; only wheat germ agglutinin and phytohemagglutinin-E competed with insulin binding to these cells, while Concanavalin A (ConA) and Erythrina cristagalli agglutinin (ECA) did not. After solubilization of the cells, however, a potent inhibition of insulin binding was also seen with ConA and ECA. This suggests that sugar determinants for ConA and ECA are present on the insulin receptor, but are not accessible at the surface of the cells. Mutant B4-2-1 cells, which are deficient in mannosylphosphoryldolichol synthase and beta-galactosidase, differed from WT cells in that ECA and ConA potently inhibited insulin binding in intact cells. This suggests that these lectin binding sites of or near the insulin receptor are more accessible at the cell surface in this mutant cell line. Mutant Lec 1 cells, deficient in N-acetylglucosaminyl-transferase I, cannot process N-linked carbohydrates from their oligomannose to their complex forms. In these cells, marked differences in the pattern of lectin inhibition were observed compared to that in WT or B4-2-1 cells. ConA exerted a strong inhibition of insulin binding to solubilized cell preparations. Its effect on intact cells was modest however, suggesting that in this mutant line exposure of the insulin receptor at the cell surface is not different from that in the WT cells. Neither ECA nor PHA inhibited [125I]insulin binding to either intact or solubilized Lec 1 cells, suggesting that the absence of sugar determinants for these two lectins may play a role in the very low insulin binding affinity previously reported in this cell line. In conclusion, these indirect studies with lectins suggest that the carbohydrate units of the insulin receptor are heterogeneous. While some may be important for proper exposure of the receptor at the cell surface, others may play a role in more intrinsic receptor properties.
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PMID:Lectins as probes of insulin receptor carbohydrate composition: studies in glycosylation mutants of Chinese hamster ovarian cells with altered insulin binding. 351 53

The immobilized lectin from the lentil (Lens culinaris) specifically binds two fractions out of the L. culinaris seed globulins. Both fractions are displaced from the lectin at low pH values. In addition, fraction I fails to interact at high ionic strengths, and fraction II in the presence of glucose or other lectin-specific sugars. The behaviour in zonal isoelectric precipitation and electrophoretical patterns indicate that both fractions represent subpopulations of the storage proteins. The interaction as demonstrated by affinity chromatography is corroborated by nephelometry: If the dissolved proteins (lectin plus fraction I or fraction II) are mixed under proper conditions the solutions become turbid. An even more pronounced interaction is observed if the lectin is reacted with both fractions at the same time. Seed albumins able to interact with the immobilized lectin include the dissolved lectin and two glycosidases (alpha-mannosidase, alpha-galactosidase) all of which are located in the protein bodies. A third glycosidase (beta-galactosidase) from outside of the protein bodies does not bind to the lectin. The results are discussed in view of the possibility that lectins may serve as packaging aids for other proteins in the protein bodies.
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PMID:In vivo binding partners of the Lens culinaris lectin. 367 73

The carbohydrate-binding properties of wheat-germ agglutinin (WGA) have been studied by using glycopeptides isolated from the cell surfaces of a cultured murine myeloid cell line (416B). The glycopeptides were passed through affinity columns of lentil lectin (LCA), concanavalin A (Con A) and WGA arranged in series so that material reaching the WGA column had failed to bind to LCA or Con A. WGA-binding glycopeptides were step-eluted with 0.01 M, 0.1 M and 0.5 M-N-acetylglucosamine (GlcNAc), to yield weak (WGA-W), intermediate (WGA-I) and strong (WGA-S) affinity fractions. WGA-W and WGA-I contained 'N'- and 'O'-linked oligosaccharides bound to separate polypeptides. WGA-S consisted almost entirely of N-linked components. Our analytical work was concentrated mainly on the N-linked fractions. In these carbohydrates WGA affinity was directly proportional to molecular size but inversely related to N-acetylneuraminic acid content. The binding of the weak-affinity fraction was dependent on N-acetylneuraminic acid, but the intermediate- and strong-binding species interacted with the lectin by N-acetylneuraminic acid-independent mechanisms. N-linked glycopeptides in each WGA-binding class were almost totally degraded to monosaccharides by the concerted action of the exoglycosidases neuraminidase, beta-galactosidase and beta-N-acetylglucosaminidase. Treatment with endo-beta-galactosidase caused partial depolymerization, yielding some disaccharides but also a heterogeneous population of partially degraded components. These findings suggest that WGA binds with high affinity to internal GlcNAc residues in large oligosaccharides containing repeat sequences of Gal beta(1----4)GlcNAc beta(1----3) (i.e. polylactosamine-type glycans). N-Acetylneuraminic acid is involved only in low-affinity interactions with WGA. WGA therefore displays an intricate pattern of saccharide specificities that can be profitably utilized for structural analysis of complex carbohydrates.
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PMID:Identification of two binding sites for wheat-germ agglutinin on polylactosamine-type oligosaccharides. 384 Jun 82

Previous studies have shown that the mechanism of spontaneous aggregation of Streptococcus mitis ATCC 903 depends on a lectin-ligand type interaction. To study the specificity of the ligand, the binding of a number of lectins of different sugar specificities to the surface of untreated, trypsin and beta-galactosidase-treated bacteria was studied by assessing aggregation. Untreated bacteria were rapidly aggregated by concanavalin A (Con A), wheat-germ agglutination (WGA) and helix pomatia lectin (HPL). Other lectins tested, e.g. peanut agglutinin and soy bean lectin, did not induce aggregation. Lectin-induced aggregation was distinguished from the spontaneous one by recording the course of aggregation and inhibition of lectins by specific sugars. Trypsin-treated bacteria lost their ability for both spontaneous and lectin-induced aggregation. beta-galactosidase-treated bacteria were aggregated only in the presence of Con A and HPL. The bacteria retained their ability for spontaneous aggregation after removal of lectins and inhibitory sugars. These findings suggest that ligand is of glycoprotein nature, since it was removed from the bacterial surface by treatment with trypsin, as shown by the inability of treated cells for both spontaneous and lectin-induced aggregation. Partial degradation of the carbohydrate part of the ligand is indicated by the ability of beta-galactosidase-treated bacteria to aggregate in the presence of Con A and HPL.
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PMID:Binding of lectins to Streptococcus mitis cells. Studies of the specificity of ligand mediated aggregation. 392 Aug 67


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