The action of N-acetylglucosaminyltransferase-V is prevented by the bisecting GlcNAc residue at the catalytic step.
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.
Sasai
Ken
K
Department of Biochemistry, Osaka University Medical School, 2-2 Yamadaoka, Suita, Japan.
Ikeda
Yoshitaka
Y
Eguchi
Hironobu
H
Tsuda
Takeo
T
Honke
Koichi
K
Taniguchi
Naoyuki
N
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
D009844:Oligosaccharides; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase; D000117:Acetylglucosamine