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H Schachter - One of the best experts on this subject based on the ideXlab platform.

  • Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme.
    Glycoconjugate journal, 1995
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, H Schachter
    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 (Ki=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 (Ki=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 (Ki=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.

  • Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme
    Glycoconjugate Journal, 1994
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, R Wilkens, G Möller, Johannes A. L. M. Dorst, H Schachter
    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 complex N -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 attaches N -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=0.13 mm ). 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=1.0–2.5 mm ). 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 bisecting N -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=0.9 mm ). 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.

  • Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme.
    Glycoconjugate journal, 1994
    Co-Authors: F Reck, Inka Brockhausen, E Meinjohanns, M Springer, R Wilkens, J A Van Dorst, H Paulsen, G Möller, H Schachter
    Abstract:

    UDP-GlcNAc:Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complex N-glycans. We have tested a series of synthetic analogues of the substrate Man"'alpha 1-6(GlcNAc"beta 1-2Man'alpha 1-3)Man beta-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attaches N-acetylglucosamine in beta 1-2 linkage to the 2"'-OH of the Man"'alpha 1-6 residue. The 2"'-deoxy analogue is a competitive inhibitor (Ki = 0.13 mM). 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 (Ki = 1.0-2.5 mM). 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"'alpha 1-6 residue are essential for binding although the 2"'- and 3"'-OH face the catalytic site of the enzyme. The 4-OH Group of the Man beta-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.(ABSTRACT TRUNCATED AT 250 WORDS)

Inka Brockhausen - One of the best experts on this subject based on the ideXlab platform.

  • Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme.
    Glycoconjugate journal, 1995
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, H Schachter
    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 (Ki=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 (Ki=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 (Ki=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.

  • Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme
    Glycoconjugate Journal, 1994
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, R Wilkens, G Möller, Johannes A. L. M. Dorst, H Schachter
    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 complex N -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 attaches N -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=0.13 mm ). 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=1.0–2.5 mm ). 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 bisecting N -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=0.9 mm ). 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.

  • Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme.
    Glycoconjugate journal, 1994
    Co-Authors: F Reck, Inka Brockhausen, E Meinjohanns, M Springer, R Wilkens, J A Van Dorst, H Paulsen, G Möller, H Schachter
    Abstract:

    UDP-GlcNAc:Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II (GlcNAc-T II; EC 2.4.1.143) is a key enzyme in the synthesis of complex N-glycans. We have tested a series of synthetic analogues of the substrate Man"'alpha 1-6(GlcNAc"beta 1-2Man'alpha 1-3)Man beta-O-octyl as substrates and inhibitors for rat liver GlcNAc-T II. The enzyme attaches N-acetylglucosamine in beta 1-2 linkage to the 2"'-OH of the Man"'alpha 1-6 residue. The 2"'-deoxy analogue is a competitive inhibitor (Ki = 0.13 mM). 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 (Ki = 1.0-2.5 mM). 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"'alpha 1-6 residue are essential for binding although the 2"'- and 3"'-OH face the catalytic site of the enzyme. The 4-OH Group of the Man beta-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.(ABSTRACT TRUNCATED AT 250 WORDS)

  • Synthese von modifizierten Oligosacchariden der N-Glycoproteine als Substrate für N-Acetylglucosaminyltransferase I☆☆☆
    Carbohydrate Research, 1992
    Co-Authors: Hans Paulsen, Folkert Reck, Inka Brockhausen
    Abstract:

    Abstract In the synthesis of modified derivatives of octyl O -(α- d -mannopyranosyl)-(1 → 3)- O -[(α- d -mannopyrasonyl)-(1 → 6)-β- d -mannopyranoside, a 4,5-epoxyPentyl, a 4-diazirinoPentyl, and a 5-(iodoacetamido)Pentyl Group were attached to the 3″-OH of the trisaccharide. The diazirino derivative may be especially suitable for photolabeling of the active site of N -acetylglucosaminyltransferase I (GlcNAcT-I). In addition, the 2′-OH Group of the above-mentioned trisaccharide was reduced to a 2′-deoxy Group and substituted 2′- O -methyl Group.

Loïc Toupet - One of the best experts on this subject based on the ideXlab platform.

  • Resorcinarene-Functionalised Imidazolium Salts as Ligand Precursors for Palladium-Catalysed Suzuki-Miyaura Cross-Couplings.
    ChemCatChem, 2013
    Co-Authors: Neslihan Sahin, David Semeril, Eric Brenner, Dominique Matt, Ismail Ozdemir, Cemal Kaya, Loïc Toupet
    Abstract:

    Three imidazolium salts based on a rigid resorcinarene platform (1-3) were synthesised and used as catalyst precursors in the Suzuki-Miyaura cross-coupling of aryl halides with phenylboronic acid. In these pro-carbene ligands, the heterocyclic moiety has one N atom connected to a C2 atom of a resorcinolic ring, and the other is substituted by an alkyl Group (R=n-propyl, iso-propyl, benzyl). The methinic C atoms of the macrocyclic core are all substituted by a Pentyl Group. The best catalytic performances were obtained by using an imidazolium/Pd ratio of 1:1. The catalytic systems displayed high activities, which increased in the order R=n-propyl (1)

  • Resorcinarene‐Functionalised Imidazolium Salts as Ligand Precursors for Palladium‐Catalysed Suzuki–Miyaura Cross‐Couplings
    ChemCatChem, 2013
    Co-Authors: Neslihan Sahin, David Semeril, Eric Brenner, Dominique Matt, Ismail Ozdemir, Cemal Kaya, Loïc Toupet
    Abstract:

    Three imidazolium salts based on a rigid resorcinarene platform (1-3) were synthesised and used as catalyst precursors in the Suzuki-Miyaura cross-coupling of aryl halides with phenylboronic acid. In these pro-carbene ligands, the heterocyclic moiety has one N atom connected to a C2 atom of a resorcinolic ring, and the other is substituted by an alkyl Group (R=n-propyl, iso-propyl, benzyl). The methinic C atoms of the macrocyclic core are all substituted by a Pentyl Group. The best catalytic performances were obtained by using an imidazolium/Pd ratio of 1:1. The catalytic systems displayed high activities, which increased in the order R=n-propyl (1)

Yong-ming Jiang - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of n-valeraldehyde modified chitosan as a matrix for hydrophobic interaction chromatography.
    Journal of chromatography. A, 2002
    Co-Authors: Yun Wang, Mingliang Guo, Yong-ming Jiang
    Abstract:

    The n-valeraldehyde modified Chitosan (Pentyl-Chitosan CL) was prepared by Schiff-base formation and hydrogenation. By studying the IR spectra of Chitosan and Pentyl-Chitosan CL, it is suggested that a Pentyl Group is linked to 2'-NH, by a C-N bond. The influence of temperature and ionic strength on the adsorption of protein on Pentyl-Chitosan CL were studied, and it was found that the behavior of adsorption met with the theory of hydrophobic interaction. The storage stability of these packing materials was also investigated, the results show storage in 20% ethanol at 4 degrees C is the most suitable condition. Alpha-amylase was purified successfully by hydrophobic interaction chromatography, using Pentyl-Chitosan CL as hydrophobic matrix. The purification factor is about 2.5 and the recovery is over 82%.

  • Evaluation of n-valeraldehyde modified chitosan as a matrix for hydrophobic interaction chromatography.
    Journal of Chromatography A, 2002
    Co-Authors: Yun Wang, Mingliang Guo, Yong-ming Jiang
    Abstract:

    Abstract The n-valeraldehyde modified Chitosan (Pentyl-Chitosan CL) was prepared by Schiff-base formation and hydrogenation. By studying the IR spectra of Chitosan and Pentyl-Chitosan CL, it is suggested that a Pentyl Group is linked to 2′-NH2 by a C–N bond. The influence of temperature and ionic strength on the adsorption of protein on Pentyl-Chitosan CL were studied, and it was found that the behavior of adsorption met with the theory of hydrophobic interaction. The storage stability of these packing materials was also investigated, the results show storage in 20% ethanol at 4 °C is the most suitable condition. α-Amylase was purified successfully by hydrophobic interaction chromatography, using Pentyl-Chitosan CL as hydrophobic matrix. The purification factor is about 2.5 and the recovery is over 82%.

Folkert Reck - One of the best experts on this subject based on the ideXlab platform.

  • Synthetic substrate analogues for UDP-GlcNAc: Man alpha 1-6R beta(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme.
    Glycoconjugate journal, 1995
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, H Schachter
    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 (Ki=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 (Ki=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 (Ki=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.

  • Synthetic substrate analogues for UDP-GlcNAc: Manα1-6R β(1-2)-N-acetylglucosaminyltransferase II. Substrate specificity and inhibitors for the enzyme
    Glycoconjugate Journal, 1994
    Co-Authors: Folkert Reck, Hans Paulsen, Inka Brockhausen, E Meinjohanns, M Springer, R Wilkens, G Möller, Johannes A. L. M. Dorst, H Schachter
    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 complex N -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 attaches N -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=0.13 mm ). 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=1.0–2.5 mm ). 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 bisecting N -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=0.9 mm ). 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.

  • Synthese von modifizierten Oligosacchariden der N-Glycoproteine als Substrate für N-Acetylglucosaminyltransferase I☆☆☆
    Carbohydrate Research, 1992
    Co-Authors: Hans Paulsen, Folkert Reck, Inka Brockhausen
    Abstract:

    Abstract In the synthesis of modified derivatives of octyl O -(α- d -mannopyranosyl)-(1 → 3)- O -[(α- d -mannopyrasonyl)-(1 → 6)-β- d -mannopyranoside, a 4,5-epoxyPentyl, a 4-diazirinoPentyl, and a 5-(iodoacetamido)Pentyl Group were attached to the 3″-OH of the trisaccharide. The diazirino derivative may be especially suitable for photolabeling of the active site of N -acetylglucosaminyltransferase I (GlcNAcT-I). In addition, the 2′-OH Group of the above-mentioned trisaccharide was reduced to a 2′-deoxy Group and substituted 2′- O -methyl Group.