ABUNDANCE OF GAL-BETA-1,3GALNAC IN O-LINKED OLIGOSACCHARIDE ON HINGE REGION OF POLYMERIZED IGA1 AND HEAT-AGGREGATED IGA1 FROM NORMAL HUMAN SERUM

Gas-phase hydrazinolysis was used to analyze the glycoform of the O-li nked oligosaccharide of human serum IgA1. In our previous report, only one glycoform was obtained from the IgA1 of healthy individuals, Howe ver, it was found to be composed of heterogeneous IgA1 components havi ng mutually different glycoforms, First, the IgA1 was separated into t wo subfractions having different affinities toward jacalin, Among them , the high-affinity subfraction was mainly composed of polymerized IgA 1, Comparative study of the carbohydrate chain showed a relative abund ance of Ga1 beta 1,3GalNAc in the polymerized form. A simultaneous ana lysis of the N-glycan of these subfractions was also carried out, Thre e major components, two biantennary and one triantennary oligosacchari des, were obtained from both subfractions and the relative contents of these components were almost the same, On the other hand, IgA1 was ar tificially polymerized by heating at 63 degrees C for 2 h, The heat-st able IgA1 was separated from the heat-aggregated material on a Sephacr yl S-300 column, The obtained heat-stable IgA2 (approximately 20%) was not further aggregated by more beating under the same conditions. The heat-stable IgA1 contained a much higher amount of the sialylated Gal beta 1,3GalNAc. Thus, it was shown that the degree of completeness of the binge. O-linked oligosaccharide might be correlated with the stab ility and polymerization process of the IgA1 molecule.