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  • 1
    Electronic Resource
    Electronic Resource
    Control of mucin synthesis: the peptide portion of synthetic O-glycopeptide substrates influences the activity of O-glycan core 1 uridine 5'-diphospho-galactose:N-acetyl-.alpha.-galactosaminyl-.alpha.-R .beta.3-galactosyltransferase (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 10206-10212 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00496a008
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  • 2
    Electronic Resource
    Electronic Resource
    Conformation of .alpha.-D-idopyranose pentaacetate (1968)
    s.l. : American Chemical Society
    The @journal of organic chemistry 33 (1968), S. 2484-2487 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo01270a068
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  • 3
    Electronic Resource
    Electronic Resource
    'Wave-type' structure of a synthetic hexaglycosylated decapeptide: A part of the extracellular domain of human glycophorin A (1999)
    Springer
    Journal of biomolecular NMR 14 (1999), S. 33-45 
    Details
    ISSN: 1573-5001
    Keywords: glycophorin A ; glycopeptide ; MD simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The three-dimensional structure of a glycopeptide, His-Thr*-Ser*-Thr*-Ser*-Ser*-Ser*-Val-Thr-Lys, with 2-acetamido-2-deoxy-α-D-galactose (GalNAc) residues linked to six adjacent amino acids from Thr-10 to Ser-15, was studied by NMR spectroscopy and molecular dynamics (MD) simulations. The hexaglycosylated decapeptide is part of the extracellular domain of human glycophorin A and shows an extended structure of the peptide backbone due to O-glycosylation. Furthermore, each GalNAc residue exhibits one and only one NOE contact from the NHAc proton to the backbone amide proton of the amino acid that the sugar is directly bound to. This indicates a strong preference for the orientation of all GalNAc residues towards the N-terminus. NOE build-up curves were used to determine 42 inter-proton distances that, in connection with φ angles of the peptide backbone obtained from 3J-coupling constants, resulted in constraints for a MD simulation in water. The NMR data and the MD simulations show a preference for an extended backbone structure. The GalNAc residues are located alternatingly on opposite sides of the backbone and reduce the flexibility of the peptide backbone. The conformation of the molecule is relatively rigid and shows a 'wave-type' 3D structure of the peptide backbone within the glycosylation cluster. This new structural element is also supported by the unusual CD spectrum of the glycopeptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008397304851
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  • 4
    Electronic Resource
    Electronic Resource
    Bausteine von Oligosacchariden, CIX. Synthese von modifizierten Oligosacchariden der N-Glycoproteine zur Untersuchung der Substratspezifität der N-Acetylglucosaminyltransferase I (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 53-66 
    Details
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Saccharides ; Glycosyltransferases ; Trichloroacetimidates ; Transferases ; Enzymes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Building Units of Oligosaccharides, CIX.  -  Synthesis of Modified Oligosaccharides of N-Glycoproteins for Substrate Specificity Studies of N-Acetylglucosaminyltransferase IA series of modified derivatives of the trisaccharide octyl α-D-Man(1→3)-[α-D-Man(1→6)]-β-D-Man were synthesized for substrate specificity studies of N-acetylglucosaminyltransferase I (GlcNAc-T I). The hydroxyl groups at C-3, C-4 and C-6 of the α(1→3)-linked Mannose were replaced by hydrogen and methoxy groups. At the α(1→6)-linked mannose the hydroxyl group at C-2 was deoxygenated and the hydroxyl groups at C-3, C-4 and C-6 were replaced by methoxy groups. The syntheses of the ten trisaccharides were carried out by the interchangeable combination of modified building blocks. The trichloroacetimidate method was favourable for all glycosylation steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950109
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  • 5
    Electronic Resource
    Electronic Resource
    Bausteine von Oligosacchariden, CX. Synthese von potentiellen Inhibitoren für die N-Acetylglucosaminyltransferase I (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 67-76 
    Details
    ISSN: 0947-3440
    Keywords: Carbohydrates ; Saccharides ; Trichloroacetimidates ; Glycosyltransferases ; Enzymes ; Transferases ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Building Units of Oligosaccharides, CX.  -  Synthesis of Potential Inhibitors of N-Acetylglucosaminyltransferase IModified derivatives of the trisaccharide octyl α-D-Man-(1→3)-[α-D-Man(1→6)]-β-D-Man were synthesized by attaching reactive groups via a pentyl spacer to the 4′-OH and 6′-OH group. Glycosylation steps were carried out by using the trichloroacetimidate method with suitable building blocks. The compounds substituted at 6′-OH are of special interest. The epoxide 27 and the diazirine 25 are reversible inhibitors of N-acetylglucosaminyltransferase I (GlcNAc-T I). Product 26 with a spacer-linked iodoacetamide is an irreversible inhibitor of GlcNAc-T I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950110
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  • 6
    Electronic Resource
    Electronic Resource
    Specificity of O-glycosylation by bovine colostrum UDP-GalNAc: polypeptide α-N-acetylgalactosaminyltransferase using synthetic glycopeptide substrates (1996)
    Springer
    Glycoconjugate journal 13 (1996), S. 849-856 
    Details
    ISSN: 1573-4986
    Keywords: polypeptide GalNAc-transferase ; substrate specificity ; glycopeptides ; O-glycosylation ; mucin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The factors determining glycosylation of mucin type glycoproteins are not well understood. In the present work, we investigated the role of the peptide moiety and of the presence of O-glycan chains on O-glycosylation by UDP-GalNAc: polypeptide α-N-acetylgalactosaminyl-transferase (ppGalNAc-T). We used purified ppGalNAc-T from bovine colostrum and a series of synthetic glycopeptide and peptide substrates most of which contained sequences derived from the tandem repeat region of MUC2 mucin. The rate of incorporation of GalNAc into Thr was significantly greater than toward Ser residues. The presence of one or two GalNAc-Thr moieties in the substrate significantly reduced enzyme activity, and this effect was more pronounced when the disaccharide Galβ1–3GalNAc was present. Thus the sequential attachment of a second GalNAc residue in the vicinity of a pre-existing GalNAc-Thr or Galβ1–3GalNAc-Thr occurs at a slower rate than primary glycosylation of carbohydrate-free peptide. Analysis of products by HPLC showed that the enzyme was selective in glycosylating peptides or glycopeptides with the PTTTPIST sequence in that the preferred primary glycosylation site was the third Thr from the aminoterminal end; secondary glycosylation depended on the site of the primary glycosylation. Negatively but not positively charged amino acids on the carboxy-terminal side of the putative secondary glycosylation site resulted in high activity suggesting charge-charge interactions of substrates with the enzyme. These studies indicate that O-glycosylation by bovine colostrum ppGalNAc-T is a selective process dependent on both the amino acid sequence and prior glycosylation of peptide substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702349
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  • 7
    Electronic Resource
    Electronic Resource
    Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme (1994)
    Springer
    Glycoconjugate journal 11 (1994), S. 210-216 
    Details
    ISSN: 1573-4986
    Keywords: Synthetic oligosaccharides ; inhibitors ; N-glycans ; N-acetylglucosaminyltransferase ; biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complexN-glycans. We have tested a series of synthetic analogues of the substrate Man‴α1-6(GlcNAc″β1-2Man′α1-3)Manβ-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attachesN-acetylglucosamine in β1-2 linkage to the 2‴-OH of the Man‴α1-6 residue. The 2‴-deoxy analogue is a competitive inhibitor (K i=0.13mm). The 2‴-O-methyl compound does not bind to the enzyme presumably due to steric hindrance. The 3‴-, 4‴- and 6‴-OH groups are not essential for binding or catalysis since the 3‴-, 4‴- and 6‴-deoxy and -O-methyl derivatives are all good substrates. Increasing the size of the substituent at the 3‴-position to pentyl and substituted pentyl groups causes competitive inhibition (K i=1.0–2.5mm). We have taken advantage of this effect to synthesize two potentially irreversible GlcNAc-T II inhibitors containing a photolabile 3‴-O-(4,4-azo)pentyl group and a 3‴-O-(5-iodoacetamido)pentyl group respectively. The data indicate that none of the hydroxyls of the Man‴α1-6 residue are essential for binding although the 2‴- and 3‴-OH face the catalytic site of the enzyme. The 4-OH group of the Manβ-O-octyl residue is not essential for binding or catalysis since the 4-deoxy derivative is a good substrate; the 4-O-methyl derivative does not bind. This contrasts with GlcNAc-T I which cannot bind to the 4-deoxy-Manβ- substrate analogue. The data are compatible with our previous observations that a ‘bisecting’N-acetylglucosamine at the 4-OH position prevents both GlcNAc-T I and GlcNAc-T II catalysis. However, in the case of GlcNAc-T II, the bisectingN-acetylglucosamine prevents binding due to steric hindrance rather than to removal of an essential OH group. The 3′-OH of the Man′α1-3 is an essential group for GlcNAc-T II since the 3′-deoxy derivative does not bind to the enzyme. The trisaccharide GlcNAcβ1-2Manα1-3Manβ-O-octyl is a good inhibitor (K i=0.9mm). The above data together with previous studies indicate that binding of the GlcNAcβ1-2Manβ1-3Manβ- arm of the branched substrate to the enzyme is essential for catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731220
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  • 8
    Electronic Resource
    Electronic Resource
    Control of glycoprotein synthesis: substrate specificity of rat liver UDP-GlcNAc:Manα3R β2-N-acetylglucosaminyl-transferase I using synthetic substrate analogues (1992)
    Springer
    Glycoconjugate journal 9 (1992), S. 180-190 
    Details
    ISSN: 1573-4986
    Keywords: GlcNAc-transferase I ; substrate specificity ; glycoprotein biosynthesis ; N-linked glycans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc: Manα3R β2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) is the key enzyme in the synthesis of complex and hybrid N-glycans. Rat liver GlcNAc-T I has been purified more than 25,000-fold (M r 42,000). TheV max for the pure enzyme with [Manα6(Manα3)Manα6](Manα3)Manβ4GlcNAcβ4GlcNAcβ-Asn as substrate was 4.6 µmol min−1 mg−1. Structural analysis of the enzyme product by proton nuclear magnetic resonance spectroscopy proved that the enzyme adds anN-acetylglucosamine (GlcNAc) residue in β1–2 linkage to the Manα3Manβ-terminus of the substrate. Several derivatives of Manα6(Manα3)Manβ-R, a substrate for the enzyme, were synthesized and tested as substrates and inhibitors. An unsubstituted equatorial 4-hydroxyl and an axial 2-hydroxyl on the β-linked mannose of Manα6(Manα3)Manβ-R are essential for GlcNAc-T I activity. Elimination of the 4-hydroxyl of the α3-linked mannose (Man) of the substrate increases theK M 20-fold. Modifications on the α6-linked mannose or on the core structure affect mainly theK M and to a lesser degree theV max, e.g., substitutions of the Manα6 residue at the 2-position by GlcNAc or at the 3- and 6-positions by mannose lower theK M, whereas various other substitutions at the 3-position increase theK M slightly. Manα6(Manα3)4-O-methyl-Manβ4GlcNAc was found to be a weak inhibitor of GlcNAc-T I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731163
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  • 9
    Electronic Resource
    Electronic Resource
    Substrate specificity and inhibition of UDP-GlcNAc:GlcNAcβ1-2Manα1-6R β1,6-N-acetylglucosaminyltransferase V using synthetic substrate analogues (1995)
    Springer
    Glycoconjugate journal 12 (1995), S. 371-379 
    Details
    ISSN: 1573-4986
    Keywords: GlcNAc-transferase V ; substrate specificity ; inhibition ; leukaemia ; N-linked glycans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc:GlcNAc β1-2Manα1-6R (GlcNAc to Man) β1,6-N-acetylglucosaminyltransferase V (GlcNAc-T V) adds a GlcNAcβ1-6 branch to bi- and triantennaryN-glycans. An increase in this activity has been associated with cellular transformation, metastasis and differentiation. We have used synthetic substrate analogues to study the substrate specificity and inhibition of the partially purified enzyme from hamster kidney and of extracts from hen oviduct membranes and acute myeloid leukaemia leukocytes. All compounds with the minimum structure GlcNAcβ1-2Manα1-6Glc/Manβ-R were good substrates for GlcNAc-T V. The presence of structural elements other than the minimum trisaccharide structure affected GlcNAc-T V activity without being an absolute requirement for activity. Substrates with a biantennary structure were preferred over linear fragments of biantennary structures. Kinetic analysis showed that the 3-hydroxyl of the Manα1-3 residue and the 4-hydroxyl of the Manβ- residue of the Manα1-6(Manα1-3)Manβ-RN-glycan core are not essential for catalysis but influence substrate binding. GlcNAcβ1-2(4,6-di-O-methyl-)Manα1-6Glcβ-pnp was found to be an inhibitor of GlcNAc-T V from hamster kidney, hen oviduct microsomes and acute and chronic myeloid leukaemia leukocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731340
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  • 10
    Electronic Resource
    Electronic Resource
    Synthetic substrate analogues for UDP-GlcNAc: Manα1-3R β1-2-N-acetylglucosaminyltransferase I. Substrate specificity and inhibitors for the enzyme (1995)
    Springer
    Glycoconjugate journal 12 (1995), S. 747-754 
    Details
    ISSN: 1573-4986
    Keywords: Synthetic oligosaccharides ; inhibitors ; N-glycans ; N-acetylglucosaminyltransferase ; biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UDP-GlcNAc:Manα1-3R β1-2-N-acetylglucosaminyltransferase I (GlcNAc-T I; EC 2.4.1.101) catalyses the conversion of [Manα1-6(Manα1-3)Manα1-6][Manα1-3]Manβ-O-R to [Manα1-6(Manα1-3)Manα1-6] [GlcNAcβ1-2Manα1-3]Manβ-O-R (R=1-4GlcNAcβ1-4GlcNAc-Asn-X) and thereby controls the conversion of oligomannose to complex and hybrid asparagine-linked glycans (N-glycans). GlcNAc-T I also catalyses the conversion of Manα1-6(Manα1-3)Manβ-O-octyl to Manα1-6(GlcNAcβ1-2Manα1-3)Manβ-O-octyl. We have therefore tested a series of synthetic analogues of Man″α1-6(Man′α1-3)Manβ-O-octyl as substrates and inhibitors for rat liver GlcNAc-T I. The 2″-deoxy and the 3″-, 4″- and 6″-O-methyl derivatives are all good substrates confirming previous observations that the hydroxyl groups of the Man″α1-6 residue do not play major roles in the binding of substrate to enzyme. In contrast, all four hydroxyl groups on the Man′α1-3 residue are essential since the corresponding deoxy derivatives either do not bind (2′- and 3′-deoxy) or bind very poorly (4′- and 6′-deoxy) to the enzyme. The 2′- and 3′-O-methyl derivatives also do not bind to the enzyme. However, the 4′-O-methyl derivative is a substrate (K m =2.6mm) and the 6′-O-methyl compound is a competitive inhibitor (K i=0.76mm). We have therefore synthesized various 4′- and 6′-O-alkyl derivatives, some with reactive groups attached to anO-pentyl spacer, and tested these compounds as reversible and irreversible inhibitors of GlcNAc-T I. The 6′-O-(5-iodoacetamido-pentyl) compound is a specific time dependent inhibitor of the enzyme. Four other 6′-O-alkyl compounds showed competitive inhibition while the remaining compounds showed little or no binding indicating that the electronic properties of the attachedO-pentyl groups influence binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00731234
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