[Prediction of glycan structures of human N-glycoproteins]

By adding the sequence beta-(1 leads to 4)-GlcNAc-beta-(1 leads to)-Asn or alpha Fuc-(1 leads to 6 or 3)-beta-(1 leads to 4)-GlcNAc-beta-(1 leads to)-Asn to the oligosaccharides isolated from human urines of mannosidosis, fucosidosis and sialidosis, we are able to reconstitute numerous structures of asparaginyl-glycans. We postulate i) that these structures which have not yet been characterized pre-exist in glycans of human glycoproteins, probably in the cytoplasm or/and the cell membrane; ii) that they are products of the action of endo-beta-N-acetyl-glucosaminidases which are protected because of the lack of exoglycosidases and accumulate in the cells, and then in the urine.