Title : Human
factor IX has
a tetrasaccharide O-glycosidically linked to
serine 61 through
the fucose residue.
Abstract :
- We have recently discovered unusual sugar chains (xylose (Xyl)-glucose (Glc) and (Xyl)2-Glc) linked to a serine residue in the epidermal growth factor ( EGF )-like domains of human and bovine clotting factors VII ( Ser-52 ), IX ( Ser-53 ), and protein Z ( Ser-53 ), in addition to bovine platelet glycoprotein thrombospondin
- We now have evidence of another modification in the first EGF-like domain of human factor IX , which proved to be a tetrasaccharide O-fucosidically linked to Ser-61
- Two large peptides containing Ser-61 ( positions 44-63), named hIX-GP1 and hIX-GP2, were first isolated from the lysyl endopeptidase-digest of human factor IX , by reversed-phase high performance liquid chromatography (HPLC)
- Data on the component sugar analysis after pyridylamination (PA) and sialic acid analysis of the isolated peptides indicated that they contained 1 mol each of galactose ( Gal ), fucose (Fuc), N-acetylglucosamine (GlcNAc), and N-acetylneuraminic acid (NeuAc), in addition to Glc and Xyl.
- hIX-GP1 was further digested with asparaginyl endopeptidase , and two glycopeptides containing Ser-61 , named N-3 ( positions 59-63) and N-9 ( positions 55-63), were isolated, respectively
- These glycopeptides were both composed of 1 mol each of Gal, Fuc, GlcNAc, Gal, Fuc, GlcNAc, and NeuAc NeuAc but did not contain Xyl and Glc.
- Moreover, the data on beta-elimination for N-9 and of the fast atom bombardment mass spectrometric analysis on peptide N-3 suggested the presence of a tetrasaccharide linked to Ser-61
- An analysis of the PA-oligosaccharide released from hIX-GP1 by hydrazinolysis followed by pyridylamination revealed that the reducing end was PA-Fuc.
- All the results support the proposal that human factor IX has a novel tetrasaccharide consisting of 1 mol each of Gal , Fuc, GlcNAc , and NeuAc , which is O-glycosidically linked to Ser-61 through the Fuc residue