UNUSUAL ANIONIC N-LINKED OLIGOSACCHARIDES FROM BOVINE LUNG

We previously described a diverse family of sulfated anionic N-linked oligosaccharides released by peptide: N-glycosidase F (PNGaseF) from c alf pulmonary artery endothelial (CPAE) cells (Roux, L., Holoyda, S,, Sundblad, G,, Freeze, H.H., and Varki, A, (1988) J. Biol. Chem. 263, 8 879-8889), Since a major fraction of the intact lung consists of endot helial cells, we reasoned that bovine lung might be a rich source of s imilar molecules, Total N-linked oligosaccharides from bovine lung ace tone powder were released by PNGaseF, labeled by [H-3]NaBH4 reduction, and the anionic fractions were studied with a variety of techniques, The sugar chains with lesser negative charge (designated Class I) shar e several properties of conventional multiantennary complex-type chain s, However, unlike the case with CPAE cells, sialic acids account only for a minority of the anionic properties and only a small proportion carry sulfate esters, A variety of different treatments indicate that most of the unexplained negative charge is due to multiple carboxylic acid groups, Resistance to beta glucuronidase and alpha-iduronidase su ggests that these may be previously undescribed modifications of mamma lian oligosaccharides. The most highly charged N-linked chains (design ated Class II) are more similar in general structure to the correspond ing ones from CPAE cells, although relatively more abundant, Their hig h charge is primarily due to chondroitin sulfate, heparin/heparan sulf ate, or keratan sulfate glycosaminoglycan chains, Sequential digestion studies suggest that a significant proportion of these molecules have more than one type of glycosaminoglycan chain associated with them, C ompositional analysis indicates the presence of xylose residues in Cla ss II, but not Class I molecules, However, unlike the case with conven tional glycosaminoglycans, these residues are not at the reducing term inus. Most previously reported structures of complex-type N-linked oli gosaccharides are derived from the glycoproteins of blood cells, plasm a, or the secretions of cultured mammalian cells, This library of N-li nked oligosaccharides from an intact mammalian organ (lung) contains a high proportion of novel anionic sugar chains whose structures are di fferent from conventional complex-type sialylated chains and only part ially related to those from CPAE cells, Further exploration of the N-l inked chains of intact mammalian tissues seems warranted.