Heifetz A, Watson C, Johnson A R, Roberts M K
J Biol Chem. 1982 Nov 25;257(22):13581-6.
Endothelial cells incorporate 35SO4 into a class of glycoproteins which are released from the cell layer into the culture medium. The incorporated 35SO4 was localized on intact oligosaccharide chains which were released from the protein either chemically by hydrazinolysis or enzymatically by a peptide: N-glycosidase activity; thus these 35S-oligosaccharides are presumably N-glycosidically linked to protein. These 35S-oligosaccharides were also isolated and analyzed as labeled glycopeptides and found to contain the terminal trisaccharide sequence sialic acid leads to galactose leads to N-acetylglucosamine. After removal of these carbohydrate residues, the remainder of this 35S-glycopeptide was susceptible to alpha-mannosidase digestion yielding a smaller 35 S-glycopeptide containing GlcNAc35SO4. Monensin (10(-8) M), a monovalent cation ionophore, inhibited the sulfation (greater than 80%) and synthesis (greater than 60%) of endothelial cell-sulfated proteoglycans which were released into the culture medium. However, neither the synthesis nor sulfation of cell-released 35S-glycoproteins was affected at similar monensin concentrations. Higher concentrations of monensin (greater 5 X 10(-8) M) inhibited the incorporation of both [3H]glucosamine and 35SO4 into cell-released glycoproteins.U
内皮细胞将35SO4掺入一类糖蛋白中，这类糖蛋白会从细胞层释放到培养基中。掺入的35SO4定位于完整的寡糖链上，这些寡糖链可通过肼解化学方式或通过肽：N-糖苷酶活性酶促方式从蛋白质上释放；因此，这些35S-寡糖可能以N-糖苷键与蛋白质相连。这些35S-寡糖也作为标记糖肽被分离和分析，发现含有末端三糖序列唾液酸导致半乳糖导致N-乙酰葡糖胺。去除这些碳水化合物残基后，这种35S-糖肽的其余部分易受α-甘露糖苷酶消化，产生一种较小的含GlcNAc35SO4的35S-糖肽。莫能菌素（10(-8)M），一种单价阳离子离子载体，抑制释放到培养基中的内皮细胞硫酸化蛋白聚糖的硫酸化（大于80%）和合成（大于60%）。然而，在类似的莫能菌素浓度下，细胞释放的35S-糖蛋白的合成和硫酸化均未受影响。更高浓度的莫能菌素（大于5×10(-8)M）抑制[3H]葡糖胺和35SO4掺入细胞释放的糖蛋白中。
