Structural Analysis of N-Linked Sugar Chains of Human Blood Clotting Factor IX

The structures of N-glycans of human blood clotting factor IX were studied. N-Glycans liberated by hydrazinolysis were N-acetylated and the reducing-end sugar residues were tagged with 2-aminopyridine. The pyridylamino (PA-) sugar chains thus obtained were purified by HPLC. Each PA-sugar chain was analyzed by two-dimensional sugar mapping combined with glycosidase digestion. The major structures of the N-linked sugar chains of human factor IX were found to be sialotetraantennary and sialotrianten-nary chains with or without fucose residues. These highly sialylated sugar chains are located on the activation peptide of the protein.