Recognition of the acceptor beta-D-GlcpNAc-(1-->2)-alpha-D-Manp- (1-->6)-beta-D-Glcp-OR by N-acetyl-glucosaminyltransferase-V: none of the hydroxyl groups on the Glc-residue are important.
The enzyme, N-acetylglucosaminyltransferase-V (GlcNAcT-V, E.C. 2.4.1.155), transfer a beta-D-GlcpNAc residue, from UDP-GlcNAc, to the OH-6 group of the Man residue in the synthetic acceptor beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->6)-beta-D-Glcp-O(CH2)7 CH3 (3). Trisaccharide 3 is an excellent substrate for the enzyme from hamster kidney with a Km value of 26 microM. In this paper we examine the contribution of the Glc residue in 3 to acceptor recognition by this enzyme. beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-O(CH2)7CH3 where the Glc residue in 3 has been deleted, was synthesized and found to be a very poor substrate with a Km value elevated to almost 2 mM. Two other analogues of 3, where the Glc residue was O-trimethylated (6) or O-tribenzylated (7), respectively, possessed Km values very near to those of 3. The Glc residue in 3 is thereby shown to present an important recognition element for GlcNAcT-V, but none of the free hydroxyl groups are required. This observation should facilitate the design of more hydrophobic and membrane-permeable analogues of 3 that are expected to function as specific glycosylation inhibitors.
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Department of Chemistry, University of Alberta, Edmonton, Canada.
Crawley
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Hindsgaul
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D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006224:Cricetinae; D007202:Indicators and Reagents; D007668:Kidney / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism*; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000378:metabolism
D007202:Indicators and Reagents; D009844:Oligosaccharides; D014537:Uridine Diphosphate N-Acetylglucosamine; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase