title: Control of glycoprotein synthesis. Characterization of (1-->4)-N-acetyl-beta-D-glucosaminyltransferases acting on the alpha-D-(1-->3)- and alpha-D-(1-->6)-linked arms of N-linked oligosaccharides.
abstract: Hen oviduct membranes contain at least three N-acetyl-beta-D-glucosaminyltransferases (GlcNAc-T) that attach a beta GlcNAc residue in (1-4)-linkage to a D-Man p residue of the N-linked oligosaccharide core, i.e., (1-->4)-beta-D-GlcNAc-T III which adds a "bisecting" GlcNAc group to form the beta-D-GlcpNAc-(1-->4)-beta-D-Man p-(1-->4)-D-GlcNAc moiety; (1-->2)-beta-D-GlcNAc-T IV which adds a GlcNAc group to the (1-->3)-alpha-D-Man arm to form the beta-D-GlcpNAc-(1-->4)-[beta-D- GlcpNAc-(1-->2)]-alpha-D-Man p-(1-->3)-beta-D-Man p-(1-->4)-D-GlcpNAc component; and (1-->4)-beta-D-GlcNAc-T VI which adds a GlcNAc group to the alpha-D-Man p residue of beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpNAc- (1-->2)]-alpha-D-Man p-R to form beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpNAc-(1-->4)]-[beta-D-GlcpNAc- (1-->2)]-alpha-D-Man p-R. We now report a novel (1-->4)-beta-D-GlcNAc-T activity (GlcNAc-T VI') in hen oviduct membranes that transfers GlcNAc to beta-D-GlcpNAc-(1-->2)-alpha-D-Man p-(1-->6)-beta-D-Man p-R to form beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p-(1-->6)- beta-D-Man p-R. The structure of the enzyme product was confirmed by 1H NMR spectroscopy, FAB-mass spectrometry and methylation analysis. Previous work with GlcNAc-T IV was carried out with biantennary substrates; we now show that hen oviduct membrane GlcNAc-T IV can also transfer GlcNAc to monoantennary beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->3)-beta-D-Man p-R to form beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p- (1-->3)-beta-D-Man p-R. The findings that GlcNAc-T VI' and IV have similar kinetic characteristics and that hen oviduct membranes can convert methyl beta-D-GlcpNAc-(1-->2)-alpha-D-Man p to methyl beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p suggest that these two activities may be due to the same enzyme. The R-group of the beta-D-GlcpNAc-(1-->2)-alpha-D-Man p-(1-->6)-beta-D-Man p (or Glcp)-R substrate has an important influence on GlcNAc-T VI' enzyme activity.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: I
authors.initials: I
authors.lastname: Brockhausen
authors.forename: G
authors.initials: G
authors.lastname: Möller
authors.forename: J M
authors.initials: JM
authors.lastname: Yang
authors.forename: S H
authors.initials: SH
authors.lastname: Khan
authors.forename: K L
authors.initials: KL
authors.lastname: Matta
authors.forename: H
authors.initials: H
authors.lastname: Paulsen
authors.forename: A A
authors.initials: AA
authors.lastname: Grey
authors.forename: R N
authors.initials: RN
authors.lastname: Shah
authors.forename: H
authors.initials: H
authors.lastname: Schachter
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002645:Chickens; D005260:Female; D006023:Glycoproteins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D009844:Oligosaccharides; D014166:Transferases