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:2.4.99.7 (sialyltransferase)
1,534 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human alpha1,3-fucosyltransferase, Fuc-TVII, a key enzyme in the biosynthesis of selectin ligands, was expressed as a soluble protein-A chimeric form in a human B cell lymphoma cell line, Namalwa KJM-1, and purified using IgG-Sepharose. The enzymatic properties of recombinant soluble Fuc-TVII were then examined. Its enzyme activity was highest at pH 7.5, and the presence of 25 mM Mn2+ was required for full activity. Fuc-TVII exhibits an acceptor specificity restricted to alpha2,3-sialylated type 2 oligosaccharides, and the apparent Km values for alpha2,3-sialyl lacto-N-neotetraose and GDP-fucose were 3.08 mM and 16.4 microM, respectively. The inhibitory effects of various nucleotides on the activity of Fuc-TVII reflected its donor specificity for the nucleotide portion of GDP. Fuc-TVII was demonstrated to be useful for the synthesis of a sialyl Lewis x hexasaccharide from lacto-N-neotetraose in combination with an alpha2, 3-sialyltransferase, ST3Gal IV. Polyethylene glycols enhanced the thermal stability of Fuc-TVII, leading to increased formation of the reaction product.
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PMID:Enzymatic characterization of human alpha1,3-fucosyltransferase Fuc-TVII synthesized in a B cell lymphoma cell line. 940 91

Galactosyltransferase, sialyltransferase, and fucosyltransferase were used to create a panel of complex oligosaccharides that possess multiple terminal sialyl-Le(x) (NeuAc alpha 2-3Gal[Fuc alpha 1-3] beta 1-4GlcNAc) and GalNAc-Le(x) (GalNAc[Fuc alpha 1-3]beta 1-4GlcNAc). The enzymatic synthesis of tyrosinamide biantennary, triantennary, and tetraantennary N-linked oligosaccharides bearing multiple terminal sialyl-Le(x) was accomplished on the 0.5 mumol scale and the purified products were characterized by electrospray MS and 1H NMR. Likewise, biantennary and triantennary tyrosinamide oligosaccharides bearing multiple terminal GalNAc-Le(x) determinants were synthesized and similarly characterized. The transfer kinetics of human milk alpha 3/4-fucosyltransferase were compared for biantennary oligosaccharide acceptor substrates possessing Gal beta 1-4GlcNAc, GalNAc beta 1-4GlcNAc, and NeuAc alpha 2-3Gal beta 1-4GlcNAc which established NeuAc alpha 2-3Gal beta 1-4GlcNAc as the most efficient acceptor substrate. The resulting complex oligosaccharides were chemically tethered through the tyrosinamide aglycone to the surface of liposomes containing phosphatidylthioethanol, resulting in the generation of glycoliposomes probe which will be useful to study relationships between binding affinity and the micro- and macro-clustering of selectin ligand.
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PMID:Enzymatic synthesis of N-linked oligosaccharides terminating in multiple sialyl-Lewis(x) and GalNAc-Lewis(x) determinants: clustered glycosides for studying selectin interactions. 964 47

The preparation of a series of sialylated and fucosylated N,N'-diacetyllactosediamine-type diantennary glycopeptides is reported. By sequential enzymatic action of jack bean beta-galactosidase, snail beta 4-N-acetyl-galactosaminyltransferase, bovine colostrum alpha 6-sialyltransferase and human milk alpha 3-fucosyltransferase, a diantennary glycopeptide obtained from asialo fibrinogen was converted at a 5-mumol scale to a series of structures occurring on the glycoprotein glycodelin A, which potentially inhibit human sperm-egg binding.
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PMID:Enzyme-assisted synthesis of Asn-linked diantennary oligosaccharides occurring on glycodelin A. 964 64

Sialyl-Lex (sLex) antigen expression recognized by KM93 monoclonal antibody was significantly down-regulated during differentiation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in human pre-B lymphocytic leukemia cell line KM3. The sLex determinants were almost exclusively expressed on O-linked oligosaccharide chains of an O-glycosylated 150-kDa glycoprotein (gp150). A low shear force cell adhesion assay showed that TPA treatment significantly inhibited E-selectin-mediated cell adhesion. Transcript and/or enzyme activity levels of alpha1-->3-fucosyltransferase, alpha2-->3-sialyltransferase, beta1-->4-galactosyltransferase, and elongation beta1-->3-N-acetylglucosaminyltransferase did not correlate with sLex expression levels. However, transcript and enzyme activity levels of core 2 GlcNAc-transferase (C2GnT) were significantly down-regulated during TPA treatment. Following transfection and constitutive expression of full-length exogenous C2GnT transcript, C2GnT enzyme activities were maintained at high levels even after TPA treatment and down-regulation of cell surface sLex antigen expression by TPA was completely abolished. Furthermore, in the transfected cells, the KM93 reactivity of gp150 was not reduced by TPA treatment, and the inhibition of cell adhesion by TPA was also blocked. These results suggest that sLex expression is critically regulated by a single glycosyltransferase, C2GnT, during differentiation of KM3 cells.
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PMID:Single glycosyltransferase, core 2 beta1-->6-N-acetylglucosaminyltransferase, regulates cell surface sialyl-Lex expression level in human pre-B lymphocytic leukemia cell line KM3 treated with phorbolester. 975 22

Structures of N-linked sugar chains are species and tissue specific and change in the course of tumorigenesis. Sialyl linkages of human placental glycoproteins are exclusively Neu5Ac alpha2-->3Gal, whereas Fuc alpha1-->2Gal and Neu5Ac alpha2-->6Gal residues are expressed in human chorionic gonadotropin and alkaline phosphatase, which are produced in human choriocarcinoma JEG-3 and BeWo cells. In the present study, to elucidate the enzymological and molecular biological basis of the structural changes that occur in the course of tumorigenesis, alpha1-->2 fucosyltransferase, alpha2-->3 and alpha2-->6 sialyltransferase activities, and the expression levels of the corresponding mRNAs were measured. The alpha2-->3 sialyltransferase activity did not change as a result of tumorigenesis; however, the alpha2-->6 siayltransferase activity and alpha1-->2 fucosyltransferase activity in JEG-3 and BeWo cells increased to levels several times higher than those in placenta Competitive PCR analysis showed that the expression levels of mRNA encoding alpha1-->2 fucosyltransferase and mRNA encoding alpha2-->6 sialyltransferase increased significantly as a result of tumorigenesis, indicating that such structural changes are regulated at the level of transcription of these glycosyltransferase genes.
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PMID:Elevation of alpha2-->6 sialyltransferase and alpha1-->2 fucosyltransferase activities in human choriocarcinoma. 976 57

A series of methyl hexopyranosiduronic acids are coupled to type I disaccharide amines to give 'trisaccharides' which have the natural N-acetyl group of the type I disaccharides replaced by uronic acids (-->saccharopeptides). These saccharopeptides are surprisingly good substrates for alpha-2,3,-sialyltransferase and fucosyltransferase III. The enzymes transfer N-acetylneuraminic acid and fucose, respectively, onto these acceptor substrates, despite the far reaching alterations, regio- and stereospecifically in the expected manner to yield sialyl-Lewis(a)-saccharopeptides.
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PMID:Glycosyltransferase catalyzed assemblage of sialyl-Lewis(a)-saccharopeptides. 983 51

Carbohydrate composition changes of glycoconjugates constituting the glycocalix of microvascular cells could be involved in the alterations of cell-cell interactions observed in diabetic retinopathy. In this field, we have recently reported that advanced glycation end products (AGEs) modify galactose, fucose and sialic acid contents of specific cellular glycoproteins. To better understand the mechanisms involved in glycoprotein modifications in diabetes, we now investigate whether glucose and AGEs could affect the activities of enzymes involved in galactose, fucose and sialic acid metabolism : glycosyltransferases (synthesis) and glycosidases (catabolism). For this, bovine retinal endothelial cells (BREC) and pericytes (BRP) were cultured in the presence of high glucose concentration or AGEs, and cell glycosidase and glycosyltransferase activities were measured. The same enzymatic activities were studied in the whole retina from streptozotocin-treated rats. The results show that high glucose concentration did not affect glycosidases and glycosyltransferases neither in BRP nor in BREC except for galactosyltransferase activities in BREC. Concerning BRP, only galactosyltransferase activities were altered by AGEs. In contrast, in BREC, AGEs increased beta-D galactosidase, alpha-L fucosidase and neuraminidase activities (+37%, +56%, 36% respectively) whereas galactosyltransferase, fucosyltransferase and sialyltransferase activities were decreased (-11%, -24% and -23% respectively). In the retina from diabetic rats, beta-D galactosidase, alpha-L fucosidase and neuraminidase activities increased (+70%, +57%, +78% respectively) whereas fucosyl and sialyltransferase decreased (-7% and -15% respectively). The possible consequence of these enzymatic activity changes could be a defect in the carbohydrate content of some glycoproteins that might participate in the endothelial cell dysfunctions in diabetic microangiopathy.
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PMID:In vitro and in vivo alterations of enzymatic glycosylation in diabetes. 1035 22

The initial steps of leukocyte adhesion depend on selectin/ligand interactions. Surface ligands on leukocytes are often modified by addition of the sialyl Lewis x (CD15s) determinant. Biosynthesis of CD15s is dependent upon alpha(2,3)sialyltransferases and alpha(1,3)fucosyltransferases. We report the isolation of an HL60 cell line variant, HL60A2, that no longer expresses CD15s. HL60A2 cells do not adhere to cytokine-stimulated endothelial cells. Enzymatic assays reveal that this cell line has normal alpha(2,3)sialyltransferase activity but is deficient in the alpha(1,3)fucosyltransferase responsible for biosynthesis of CD15s (FUT7). The fucosyltransferase that constructs the non-sialylated antigen, Lewis x (CD15), is expressed at high levels (FUT4). Transcript analyses show that FUT7 and FUT4 are inversely expressed in HL60 and variant cell lines. HL60A2 cells provide a tool to study the regulation of selectin ligands and corresponding human fucosyltransferase genes.
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PMID:A cloned CD15s-negative variant of HL60 cells is deficient in expression of FUT7 and does not adhere to cytokine-stimulated endothelial cells. 1041 54

Biosynthesis of carbohydrate structures is tissue-specific and developmentally regulated by glycosyltransferases like fucosyl-, sialyl- and N-acetylglucosaminyltransferases. During carcinogenesis, aberrant glycosylation leads to the development of tumor subpopulations with different adhesion properties. The aim of this contribution was to directly compare mRNA expression of several glycosyltransferases in surgical specimens of gastric carcinomas. Carcinoma specimens were classified and characterized according to the WHO/UICC system. In each case, the expression of 12 glycosyltransferase enzymes was studied simultaneously by RT-PCR. For semi-quantitative analysis, amplification of the sample sequence was compared with that of beta-actin, co-amplified within the same tube. Expression of N-acetylglucosaminyltransferase V in gastric carcinomas was significantly enhanced compared to normal tissue. Also, expression of sialyltransferase ST3Gal-IV and fucosyltransferase FT-IV was significantly enhanced in carcinoma tissue. No significant differences in glycosyltransferase expression were found in samples positive for Helicobacter pylori or between the different gastric regions. Thus, carcinogenesis is characterized by specific alterations in mRNA expression of several glycosyltransferases. Future studies will show whether RT-PCR detection of the expression of these enzymes could be helpful for prognostic purposes.
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PMID:Altered mRNA expression of glycosyltransferases in human gastric carcinomas. 1043 38

Activated Th1 CD4 T cells bind to P-selectin and migrate into inflamed tissue, whereas Th2 cells do not. We show that alpha(1, 3)-fucosyltransferase VII (FucT-VII) and alpha(2, 3)-sialyltransferase IV (ST3GalIV), which are crucial for the biosynthesis of functional P-selectin ligands, are absent in naive CD4 T cells, but are rapidly up-regulated upon activation. Th1 or Th2 differentiation in the presence of polarizing cytokines leads to down-regulation of FucT-VII mRNA selectively in Th2 but not in Th1 cells. Influencing the differentiation by varying the priming dose of antigenic peptide results in similar FucT-VII down-regulation only in Ag-specific Th2 cells. ST3GalIV levels remain elevated. FucT-VII and ST3GalIV mRNAs are also up-regulated by Th1 cells primed in vivo and recruited into the lymph nodes draining delayed-type hypersensitivity sites. We identify FucT-VII gene expression as a principal difference between Th1 and Th2 cells, and underscore the importance of FucT-VII and ST3GalIV expression for the biosynthesis of functional selectin ligands.
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PMID:Alpha(1,3)-fucosyltransferase VII and alpha(2,3)-sialyltransferase IV are up-regulated in activated CD4 T cells and maintained after their differentiation into Th1 and migration into inflammatory sites. 1049 Sep 70


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