Structural analysis of the sugar chains of human urinary thrombomodulin

The sugar chains of human urinary thrombomodulin were studied. N- and O-lin ked sugar chains were simultaneously liberated by hydrazinolysis followed b y N-acetylation and were tagged with 2-aminopyridine. Then the structures o f the N- and O-linked pyridylamino (PA-) sugar chains were analyzed by two- dimensional sugar mapping combined with exoglycosidase digestion. The major N-linked sugar chains of human urinary thrombomodulin were found to be mon osialo- and disialofucosylbiantennary chains, while the major O-linked suga r chain was +/- Sia alpha2-3Gal beta1-3(+/- Sia alpha2-6)GalNAc. Thrombomod ulin also contained the reported structure SO4-3GlcA beta1-3Gal beta1-3(+/- Sia alpha2-6)Gal beta1-4Xyl [H. Wakabayashi, S. Natsuka, T. Mega, N. Otsuk i, AL Isaji, M. Naotsuka, S. Koyama, T. Kanamori, M Sakai, and S. Hase (199 9) J. Biol. Chem. 274, 5436-5442]. In addition to these sugar chains, a sin gle Glc was linked to Ser 287.