Carbohydrate structures of human interleukin 5 expressed in Chinese hamster ovary cells

The asparagine-linked sugar chains of recombinant human interleukin 5 produced by Chinese hamster ovary cells were released quantitatively as oligosaccharides by hydrazinolysis. After N-acetylation followed by NaB3H4 reduction, each oligosaccharide was isolated by paper electrophoresis and serial lectin column chromatography. Study of their structures by sequential exoglycosidase digestion in combination with methylation analysis, revealed that they are bi-, tri-, and tetraantennary complex-type with fucosylated and non-fucosylated trimannosyl cores and high mannose type sugar chains. More than 80% of the sugar chains occur as biantennary complex-type sugar chains. Although acidic oligosaccharides amount to only 14% of the total oligosaccharides, their sialic acid residues occur exclusively as the Sia alpha 2----3Gal group. Removal of the sugar moiety from intact recombinant human interleukin 5 produced a 2.5-fold increase of its activity to induce IgM secretion.