Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.99.6 (sialyltransferase)
 1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A beta-D-galactoside alpha 2 leads to 6 sialyltransferase was purified 500-fold in 14% yield from 14-day embryonic chicken liver. Characterization of the product of the sialyltransferase catalysis was accomplished by separation and permethylation of double-labelled ([14C]NeuAc, [3H]Gal) oligosaccharides following their release from the glycoprotein fetuin by hydrazinolysis. The enzyme transfers NeuAc to Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to)R-terminated oligosaccharides; no activity was found towards Gal(beta 1 leads to 3)GalNAc(alpha 1 leads to)R structures. The trisaccharide. NeuAc(alpha 2 leads to 6)Gal(beta 1 leads to 4)Glc, was shown to be a good inhibitor of the sialyltransferase. Kinetic investigations of the enzyme indicate it to have a sequential, random bi-bi mechanism.
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PMID:Kinetic parameters of a beta-D-galactoside alpha 2 leads to 6 sialyltransferase from embryonic chicken liver. 675 14

Rat liver Golgi was found to contain a sialyltransferase activity which would convert lacto-N-tetraose (Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc) to LS-tetrasaccharide a (NeuAc alpha 2 goes to 3Gal beta 1 goes to 3GlcNAc beta 1 goes to 3Gal beta 1 goes to 4Glc). The enzyme has been partially purified by affinity chromatography on CDP-hexanolamine agarose. Of the glycoprotein substrates examined, it utilizes the Gal beta 1 goes to 3GlcNAc sequence found on the asparagine-linked oligosaccharides of prothrombin as its preferred acceptor substrate, and thus has been tentatively designated a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase. The partially purified enzyme has an acceptor specificity distinct from other purified mammalian sialyltransferases which synthesize the NeuAc alpha 2 goes to 3Gal beta 1 goes to 3 GalNAc and NeuAc alpha 2 goes to 6 GalNAc sequences common to oligosaccharides O-linked to threonine or serine and the NeuAc alpha 2 goes to 6Gal beta 1 goes to 4GlcNAc sequence found on oligosaccharides N-linked to asparagine.
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PMID:Identification of a Gal beta 1 goes to 3GlcNAc alpha 2 goes to 3 sialyltransferase in rat liver. 706 22

High-pressure liquid chromatography was used to identify the sialo-oligosaccharide products obtained after sialylation of [14C]Gal-GalNAc-protein in vitro by an ovine submaxillary-gland microsomal fraction. Among other products, two isomeric trisaccharides could be identified. NeuAc alpha 2 leads to 3Gal beta 1 leads to 3GalNAcol and Gal beta 1 leads to 3-(NeuAc alpha 2 leads to 6)GalNAcol respectively, indicating that ovine submaxillary gland contains two sialyltransferases acting on mucin-type acceptors, a beta-galactoside alpha 2 leads to 3 sialyltransferase and a N-acetylgalactosaminide alpha 2 leads to 6 sialyltransferase. This conclusion was fully supported by methylation analysis of the two trisaccharide products.
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PMID:Specificity of ovine submaxillary-gland sialyltransferases. Application of high-pressure liquid chromatography in the identification of sialo-oligosaccharide products. 708 99

A sialyltransferase activity present in 7- to 12-day-old embryonic chicken brain catalyzes the transfer of sialic acid from CMP-sialic acid to the terminal galactose residue of [3H]nLcOse4Cer ([3H]Gal(beta 1-4).GlcNAc(beta 1-3)Gal(beta 1-4)Glc-Cer) to form NeuAc(alpha 2-3)-[3H]nLcOse4Cer (LM1 ganglioside). The product is sialidase-labile (96%), and the NeuAc group is linked to O-3 of the terminal galactose residue. The (alpha 2-3) linkage between sialic acid and the terminal galactose was determined on the basis of identification of 2,4,6-tri-O-methyl[3H]galactose obtained after hydrolysis of the permethylated enzymatic product. The CMP-sialic acid:nLcOse4Cer (alpha 2-3)sialyltransferase activity sediments (90%) at the junction of 1.2 M and 1.5 M on a discontinuous sucrose density gradient when still membrane bound (insoluble in 0.2% Triton X-100). The enzyme preparation also catalyzes the transfer of sialic acid from CMP-sialic acid to O-3 of GgOse4Cer (Gal(beta 1-3)GalNAc(beta 1-4)Gal(beta 1-4)Glc-Cer) to form NeuAc (alpha 2-3)GgOse4Cer (GM1b). Substrate inhibition studies indicate that these two reactions are probably catalyzed by the same enzyme.
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PMID:Biosynthesis in vitro of sialyl(alpha 2-3)neolactotetraosylceramide by a sialyltransferase from embryonic chicken brain. 713 Jan 78

A Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferse and a Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase have been purified 23,000- and 860,000-fold to homogeneity from Triton CF-54 extracts of rat liver membranes. The two enzymes were concentrated by affinity chromatography on CDP-hexanolamine-agarose and resolved by NaCl gradient elution from the same adsorbent. Final purification of the Gal beta 1 to 4GlcNAc alpha 2 to 6 sialytransferase, the most abundant enzyme, was achieved by specific elution from CDP-agarose with CDP. The Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase was also purified further by CDP elution from CDP-agarose, but final purification required affinity chromatography on an adsorbent prepared by coupling asialoprothrombin to cyanogen bromide-activated agarose. Asialoprothrombin contains the terminal sequence Gal beta 1 to 3GlcNAc on N-linked oligosaccharides and is the best acceptor substrate of the enzyme (Km congruent to 6 microM). The Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase was found to bind to asialoprothrombin-agarose in the presence of CDP and could be eluted with a solution containing 0.2 M lactose and no CDP. Sodium dodecyl sulfate-gel electrophoresis of the Gal beta 1 to 4GlcNAc alpha 2 to 6 and Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferases revealed a single major protein band for each enzyme with apparent molecular weights of 40,500 and 44,000, respectively. Rabbit antibodies raised to the Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferase inhibit its enzymatic activity greater than 99% but caused little or no inhibition of Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialytransferase. Moreover, the Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferase quantitatively bound to a column containing antibody adsorbed to Protein A-agarose, while the Gal beta 1 to 3(4) GlcNAc alpha 2 to 3 sialyltransferase did not bind. This demonstrated that the two sialyltransferases are antigenically unrelated and formed the basis for removal of contaminating Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferase from solutions of the Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase. Enzymatic characterization of the two sialyltransferases suggests that their major biological roles are in the terminal glycosylation of N-linked oligosaccharides of glycoproteins. (Weinstein, J., de Souza-e-Silva, U., and Paulson J. C. (1982) J. Biol. Chem. 257, 13845-13853. The alpha 2 to 6 sialyltransferase efficiently forms the NeuAc alpha 2 to 6Gal beta 1 to 4GlcNAc sequence, and the alpha 2 to 3 sialyltransferase forms the NeuAc alpha 2 to 3Gal beta 1 to 3GlcNAc and NeuAc alpha 2 to 3Ga; beta 1 to 4GlcNAc sequences.
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PMID:Purification of a Gal beta 1 to 4GlcNAc alpha 2 to 6 sialyltransferase and a Gal beta 1 to 3(4)GlcNAc alpha 2 to 3 sialyltransferase to homogeneity from rat liver. 714 79

Smooth membrane preparations of 13-day embryonic chicken livers, characterized by electron microscopy and marker enzyme analyses, have been found to contain sialyltransferase activity which displayed precise acceptor specificity. One sialyltransferase transferred N-acetyl-neuraminic acid (NANA) and gal beta 1 leads to 4glycNAc beta 1 leads R structures. Evidence based on competition studies suggests that a second enzyme is present transferring this sugar to a gal beta 1 leads to 3gal-NAc alpha 1 leads to R structure. The enzyme capable of adding NANA to gal beta 1 leads to 4glcNAc beta 1 leads to R structures has a pH optimum of 5.5, a temperature optimum of 30 degrees C, and half-saturating values of 17 muM for CMP-NANA and 180 muM for galactoside termini on desialyzed alpha 1-acid glycoprotein. It is activated about 10-fold by Triton X-100, has no exogenous divalent cation requirement, and is inhibited by CTP, CDP, and CMP. The enzyme requires carbohydrate structures underlying the gal beta 1 leads to 4glcNAc terminus for maximal catalytic activity; the necessity of such precise specificities of sialyltransferases is discussed in the light of recent structural evidence for the carbohydrate moieties of several glycoproteins.
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PMID:The specificity of sialyltransferase activity in smooth membrane fractions of embryonic chicken liver. 722 24

Three melanomas of C57BL/6 mice (BL6, JB/MS, and JB/RH) share several phenotypic properties. All these cells contain melanoma-specific ecotropic C-type retrovirus that encodes melanoma-associated antigen recognizable by MM2-9B6 mAb. They do not express H-2Kb molecules, and the alpha-galactosyl epitopes (Gal alpha 1-3Gal beta 1-4GlcNAc-R) they fail to react with soybean agglutinin (SBA), peanut agglutinin (PNA), and vicia villosa (VV) lectins. Previously, we found that failure of BL6 melanoma cells to express alpha-galactosyl epitopes is due to down-regulation of alpha 1,3 galactosyltransferase (alpha 1,3GT) gene expression. To evaluate the possible role of alpha-galactosyl cell membrane carbohydrates in regulation of metastatic properties, individual clones isolated from BL6, JB/MS, and JB/RH melanomas were transfected with alpha 1,3GT cDNA. This resulted in appearance of alpha-galactosyl epitopes, as well as of carbohydrates reacting with SBA, PNA, or VV lectins, but did not affect expression of H-2 class I molecules or melanoma-associated antigen. Appearance of SBA, PNA, and VV lectin binding carbohydrates in the alpha 1,3GT gene-transfected melanoma cells is a result of reduction of cell membrane sialylation and unmasking of these carbohydrates. Reduction in cell membrane sialylation in the alpha 1,3GT gene-transfected melanoma cells is probably due to the competition between alpha 1,3GT with alpha 2,3 sialyltransferase or alha 2,6 sialyltransferase for the common acceptor N-acetyllactosamine in the Golgi apparatus. As a result of this competition, cell membranes of alpha 1,3GT gene-transfected melanoma cells became galactosylated and less sialylated. In parallel with alteration of cell membrane carbohydrates, transfection of the alpha 1,3GT gene leads to the loss of metastatic properties of the transfected melanoma cells in the immunocompetent and immunosuppressed C57BL/6 mice. Thus, the use of specific glycosyltransferase cDNA transfection presents direct experimental confirmation of the importance of cell membrane carbohydrates in the regulation of metastatic properties of tumor cells.
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PMID:Alterations of cell surface carbohydrates and inhibition of metastatic property of murine melanomas by alpha 1,3 galactosyltransferase gene transfection. 754 89

A stable, sialyltransferase-deficient mutant of Neisseria gonorrhoeae strain F62 totally defective in CMP-NANA-dependent lipopolysaccharide (LPS) sialylation was isolated by insertion mutagenesis with transposon Tn 1545-delta 3 and screened for unlabelled colonies following incubation with CMP-14C-NANA. In contrast to the parental strain which became serum resistant on incubation with CMP-NANA or blood cell extracts, the mutant, JB1, remained serum sensitive. French press extracts of strain F62 catalysed LPS sialylation, but corresponding extracts of the mutant were inactive. Five LPS components were detected by SDS-PAGE in the parental strain. Five components of the same Mr were also found in the mutant. Three identical components were detected by Western blotting using MAb 3F11, which recognizes the Gal beta 1-4GlcNAc groups in the conserved LPS components of F62 which can be sialylated. The mutant, JB1, is therefore deficient in the sialyltransferase that is essential for both LPS sialylation and conversion of serum-sensitive gonococci to serum resistance by either CMP-NANA or blood cell extracts. No evidence was obtained for an LPS sialylation pathway by blood cell extracts that is independent of CMP-NANA.
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PMID:A serum-sensitive, sialyltransferase-deficient mutant of Neisseria gonorrhoeae defective in conversion to serum resistance by CMP-NANA or blood cell extracts. 756 13

Cell surface expressed lactosaminyl glycans were determined on live cells by flow cytometry using a sialyltransferase mediated labeling procedure. Fluorescent CMP-sialic acid and Gal beta 1,4GlcNAc alpha 2,6-sialyltransferase were applied to probe expression of acceptor glycans on untreated or sialidase pretreated erythrocytes. After enzymatic fluorescence labeling, erythrocytes were treated with endo-beta-galactosidase or trypsin to distinguish polylactosaminyl- and complex-type glycans. The expression of lactosaminyl sequences on cord- was 20% lower than on adult cells. After sialidase treatment fluorescence incorporation on both cell types increased twofold compared to untreated cells indicating a low sialylation extent. A recombinant alpha 2,3-sialyltransferase was preferentially labeling polylactosaminyl glycans. Taking advantage of the different fine specificity as determined here, alpha 2,6- and alpha 2,3-sialyltransferase can be applied to distinguish certain types of lactosaminyl glycans.
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PMID:Enzymatic analysis of cell surface lactosaminyl glycans by flow cytometry. 757 5

The product of the MUC1 gene, the polymorphic epithelial mucin (PEM) is aberrantly glycosylated in breast and other carcinomas, resulting in exposure of normally cryptic peptide epitopes. PEM expressed by breast cancer cells contains more sialylated O-glycans and has a lower GlcNAc content than that expressed by normal cells. The exposure of peptide epitopes is thus thought to be due to the sugar side chains being shorter on the tumour-associated mucin. To investigate possible mechanisms underlying the different pattern of glycosylation in breast cancer cells, we analysed the pathways involved in the biosynthesis of O-glycan chains of mucins in normal and cancerous mammary epithelial cells. An immortalized mammary epithelial cells line originating from normal human milk. MTSV1-7, and three human breast cancer cell lines, BT20, MCF-7 and T47D, were studied. Glycosyltransferase activities assembling, elongating and terminating O-glycan core-1 [Gal beta 1-3GalNAc alpha-R] and core-2 [GlcNac beta 1-6 (Gal beta 1-3) GalNAc alpha-R] were present in the normal mammary cell line. Many of the glycosyltransferase activities were also expressed at variable levels in breast cancer cells. However, a sialyltransferase activity (CMP-sialic acid Gal beta 1-3GalNAc alpha 3-sialyltransferase) was increased several fold in all three cancer cell lines. Moreover, mammary cancer cell lines BT20 and T47D have lost the ability to synthesize core-2, as shown by the lack of UDP-GlcNAc: Gal beta 1-3GalNAc (GlcNAc to GalNAc) beta 6-GlcNAc-transferase activity, which corresponded to the absence of the mRNA transcript. However, MCF-7 breast cancer cells expressed this enzyme. Thus, the mechanism for the exposure of peptide epitopes in BT20 and T47D cells is proposed to be the loss of core-2 branching leading to shorter, sialylated O-glycan chains. A different mechanism is proposed for MCF-7 breast cancer cells.
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PMID:Mechanisms underlying aberrant glycosylation of MUC1 mucin in breast cancer cells. 758 8


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