Synthesis of a novel class of sulfated glycoproteins in embryonic liver and lung.

Slices from various organs and tissues of 14-day-old chick embryos synthesize a novel class of glycoproteins containing sulfated oligosaccharide chains that are not released from the polypeptides under conditions that cleave O-glycosidically linked chains. Of the tissues examined, embryonic lung and liver were the most active in incorporating [35S]O4 into these oligosaccharide chains, which were analyzed as glycopeptides following Pronase digestion. These low molecular weight sulfated glycopeptides were resistant to several chemical and enzymatic treatments that degrade a variety of high molecular weight sulfated glycosaminoglycans. The incorporation of both [3H]glucosamine and [35S]O4 into the glycopeptides was inhibited by tunicamycin, an antibiotic which inhibits the N-glycosylation of proteins. These observations, coupled with the finding that these chains were resistant to beta elimination, suggest that this novel type of sulfated oligosaccharide is N-glycosidically linked to protein. The sulfated glycopeptides from chick embryonic lung were characterized as containing terminal fucose and sialic acid residues as well as O-sulfated N-acetylglucosamine residues. Comparable studies with slices of adult liver and lung indicated that they were far less active in the synthesis of this class of sulfated glycopeptides, even though these organs, like those from the embryo, actively synthesize sulfated glycosaminoglycans.