Structural elucidation of the disulfated oligosaccharide from bovine lutropin

The Asn-linked oligosaccharides of the pituitary hormone lutropin (LH) contain both sulfate and GalNAc. Bovine pituitary explants incorporate [3H]glucosamine, [3H]mannose, [3H]fucose, and [35S]sulfate into the Asn-linked oligosaccharides of LH. Endoglycosidase F or N-glycanase releases the [3H]glucosamine- and [3H]mannose-labeled oligosaccharides from the protein, which resolve on anion-exchange high pressure liquid chromatography as neutral (S-0), mono- (S-1), and disulfated (S-2) species. Based on sequential enzyme digestion, methylation, periodate oxidation, and nuclear magnetic resonance studies, the proposed structure for S-2 is as follows: formula see text. Sulfate is confined to position 3 or 4 of GalNAc based on periodate and methylation data and can be removed by methanolysis. The presence of beta-linked GalNAc at a position typically occupied by Gal has not previously been observed.