title: Elongation of both branches of biantennary backbones of oligo-(N-acetyllactosamino)glycans by human serum (1----3)-N-acetyl-beta-D- glucosaminyltransferase.
abstract: Partial reactions catalyzed by a (1----3)-N-acetyl-beta-D- glucosaminyltransferase (EC2.4.1.149), known to be present in human serum, were studied by use of biantennary "backbone" saccharides of oligo-N-acetyllactosamine-type as acceptors. Incubation of the radiolabeled blood-group I-active hexasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp- (1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-GlcNAc (1) and UDP-GlcNAc with serum gave first a transient 1:1 mixture of two isomeric heptasaccharides, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D- GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D- Galp-(1----4)-D-GlcNAc (2) and beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-GlcpNAc-(1----3)- beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-Glc NAc (3), showing that both branches of 1 react equally well. The two heptasaccharides reacted further in the incubation mixture to form the radiolabeled octasaccharide, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[be ta-D- GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Ga lp- (1----4)-D-GlcNAc (4); during this second reaction, the composition of the heptasaccharide mixture remained unchanged, indicating that 2 and 3 reacted at approximately equal rates. The heptasaccharides 2 and 3 could not be separated from each other, but they could be detected, identified, and quantitatively determined by stepwise enzymic degradations. Partial (1----3)-N-acetyl-beta-D-glucosaminylation reactions, carried out with another acceptor, the branched pentasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta- D- GlcpNAc-(1----6)]-beta-D-Gal (11), revealed that it reacted also equally well at both branches.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Institute of Biotechnology, University of Helsinki, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Vilkman
authors.forename: R
authors.initials: R
authors.lastname: Niemelä
authors.forename: L
authors.initials: L
authors.lastname: Penttilä
authors.forename: J
authors.initials: J
authors.lastname: Helin
authors.forename: A
authors.initials: A
authors.lastname: Leppänen
authors.forename: A
authors.initials: A
authors.lastname: Seppo
authors.forename: H
authors.initials: H
authors.lastname: Maaheimo
authors.forename: S
authors.initials: S
authors.lastname: Lusa
authors.forename: O
authors.initials: O
authors.lastname: Renkonen
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000606:Amino Sugars / Q000378:metabolism*; D002240:Carbohydrate Sequence; D005696:Galactosidases / Q000378:metabolism; D005964:Glucosyltransferases / Q000097:blood / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000096:biosynthesis*; D006801:Humans; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000606:Amino Sugars; D006025:Glycosaminoglycans; D009844:Oligosaccharides; C000458:N-acetyllactosamine; D005964:Glucosyltransferases; D005696:Galactosidases; D000117:Acetylglucosamine