Immunochemistry of highly branched N-glycans. Terminal N-acetyl-D-glucosamine (GlcNAc) cluster antigens contain epitopes composed of terminal GlcNAc residues linked to mannose.
We have previously demonstrated by the immunoperoxidase method the presence of a chicken heterophile antigenic determinant (CHAD-1) in medullary lymphocytes of the bursa of Fabricius and thymus as well as in some nonlymphoid cells. It has been found that the anti-CHAD-1 antibody could be neutralized by absorption with several glycoproteins or glycopeptides containing highly branched, asparagine-linked oligosaccharides terminating in N-acetylglucosamine residues. In the present study, fetuin, desialo-fetuin, and a series of 27 highly purified oligosaccharides with well-defined structures were used to investigate the chemical composition and fine structure of the CHAD-1 epitope. It was shown that anti-CHAD-1 antibody binds to oligosaccharides with at least three terminal N-acetyl glucosamine residues at the nonreducing end. These residues may be linked beta 1-2, beta 1-4, or beta 1-6 to one, two, or three different mannose residues. The antibody combining site accommodates at least four carbohydrate residues. Oligosaccharides containing five or six terminal N-acetylglucosamine residues at the nonreducing end demonstrated the highest immunoreactivity with the anti-CHAD-1 antibody. Substitution of terminal N-acetylglucosamine residues with galactose, or with galactose and sialic acid, masks CHAD-1. On the basis of this work, epitopes that react with the anti-CHAD-1 antibody will be renamed terminal N-acetylglucosamine cluster antigens (TGCA). Anti-TGCA antibody has potential use in the monitoring of biosynthetic processing of asparagine-linked oligosaccharides and in studies of their cellular distribution and functions.
Chechik
B E
BE
Research Institute, Mount Sinai Hospital, Toronto, Ont., Canada.
Brockhausen
I
I
D000117:Acetylglucosamine / Q000276:immunology*; D000818:Animals; D000939:Epitopes / Q000032:analysis*; D005944:Glucosamine / Q000031:analogs & derivatives*; D006023:Glycoproteins / Q000138:chemical synthesis; D007124:Immunoenzyme Techniques; D008358:Mannose / Q000378:metabolism*; D009844:Oligosaccharides / Q000138:chemical synthesis; D011134:Polysaccharides / Q000032:analysis*; D011817:Rabbits
D000939:Epitopes; D006023:Glycoproteins; D009844:Oligosaccharides; D011134:Polysaccharides; D005944:Glucosamine; D008358:Mannose; D000117:Acetylglucosamine