SINGLE-STEP ISOLATION METHOD FOR 6 GLYCOFORMS OF HUMAN ALPHA(1)-ACID GLYCOPROTEIN BY HYDROXYLAPATITE CHROMATOGRAPHY AND STUDY OF THEIR BINDING-CAPACITIES FOR DISOPYRAMIDE

A single-step isolation method for the glycoforms of human serum alpha (1)-acid glycoprotein (AAG) using a hydroxylapatite column under a gra dient elution program was developed. The concentrations of N-acetylneu raminic acid and monosaccharides (fucose, N-acetylglucosamine, galacto se and mannose) of six AAG glycoforms were determined by the pulsed am perometric detection method, For each AAG glycoform, significant sex-r elated differences in carbohydrate content have been observed only for AAG glycoforms two and six, and not for each AAG glycoform. The relat ionship between the extent of the branch in the glycan chain and the b inding capacity to disopyramide were examined. Female AAG contained hi ghly sialylated AAG glycoforms compared to male glycoforms. Conversely , male AAG was rich in the lower sialylated AAG glycoform. Furthermore , it was found that the drug binding capacity decreases with increasin g branching of the glycan chain. This suggests that the binding sites of AAG are hindered by a relatively large carbohydrate moiety, such as tetraantennary structures.