Elongation of both branches of biantennary backbones of oligo-(N-acetyllactosamino)glycans by human serum (1----3)-N-acetyl-beta-D- glucosaminyltransferase

• Published in: Carbohydrate research Vol. 226; no. 1; p. 155
• Main Authors: Vilkman, A, Niemelä, R, Penttilä, L, Helin, J, Leppänen, A, Seppo, A, Maaheimo, H, Lusa, S, Renkonen, O
• Format: Journal Article
• Language: English
• Published: Netherlands 16-03-1992
• Subjects: Acetylglucosamine - metabolism; Amino Sugars - metabolism; Carbohydrate Sequence; Galactosidases - metabolism; Glucosyltransferases - blood; Glucosyltransferases - metabolism; Glycosaminoglycans - biosynthesis; Humans; Molecular Sequence Data; Oligosaccharides - chemistry; Oligosaccharides - metabolism
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(92)84061-V

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.