Carbohydrate structures of a normal counterpart of the carcinoembryonic antigen produced by colon epithelial cells of normal adults

Normal Faecal antigen-2 (NFA-2) and non-specific crossreactingantigen-2 (NCA-2), cross-reacting with anticarcinoembryonicantigen (CEA) antibodies, were found in normal human faececand meconium, respectively. Because NFA-2, NCA-2 and CEA areconsidered as the same gene products, NFA-2 and NCA-2 shouldbe normal counterparts of CEA produced by colon epithelial cellsof normal adults and fetuses, respectively. Comparison of sugarchain structures of these three antigens is indispensable inorder to unravel the stnaural alteration induced by malignanttransformation and development of colon epithelial cells. Thesugar chain structures of CEA (Yamashita,K. et al., Cancer Res.,47,3451–3459,1987) and NCA-2 (Yarnashita,K. et al., J.Bid Chem, 264,17873-17881,1989) were previously reported. Inthis paper, the structures of the oligosaccharides releasedfrom four NFA-2 samples by hydrazinolysis were studied by meansof lectin-affinity column chromatography, endo- and em-glycosidasedigestion, methylation analysis, hydrazinolys-nitrous acid deaminationand electrospray ionization mass spectrometry. NFA-2 contains24–27 mol of N-linked sugar chains/molecule, which issimilar to NCA-2 (27 mol) and CEA (24–27 mol). In contrastto CEA, which contains {small tilde} 8% high-mannose-type sugarchains all sugar chains of NFA-2 are mono- to tetra-antennarycomplex-type chains having four types of tri-mannosyl cores,with or without bisecting N-acetylglucosamine and fucose residues.The structures of their outer chain moieties comprise Galß1