title: The action of N-acetylglucosaminyltransferase-V is prevented by the bisecting GlcNAc residue at the catalytic step.
abstract: Using a purified protein and bisected acceptor oligosaccharides, we demonstrate that N-acetylglucosaminyltransferase (GnT)-V transfers a N-acetylglucosamine residue via a beta1,6-linkage to the bisected oligosaccharides. We also kinetically characterized the substrate specificity of GnT-V with respect to the bisected oligosaccharide. Although the K(m) values for the bisected acceptors were comparable to that for a non-bisected acceptor, the V(max) values for the bisected acceptors were much lower than that for the non-bisected acceptor. These findings suggest that the acceptor specificity of GnT-V is determined by the catalytic process rather than by its binding to the substrate. It was also found that the presence of the 2-N-acetyl group in the bisecting monosaccharide moiety plays a critical role in determining the catalytic efficiency of the enzyme.
authors.affiliation: Department of Biochemistry, Osaka University Medical School, 2-2 Yamadaoka, Suita, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Sasai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Hironobu
authors.initials: H
authors.lastname: Eguchi
authors.forename: Takeo
authors.initials: T
authors.lastname: Tsuda
authors.forename: Koichi
authors.initials: K
authors.lastname: Honke
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002384:Catalysis; D004789:Enzyme Activation; D017351:N-Acetylglucosaminyltransferases / Q000037:antagonists & inhibitors*; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009844:Oligosaccharides; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase; D000117:Acetylglucosamine