Uniformity of glycans within molecular variants of alpha-protease inhibitor with distinct affinity for concanavalin A.

Human alpha 1-protease inhibitor contains four asparagine-linked carbohydrate chains per molecule. Three types of carbohydrate chains were released from the polypeptide backbone by hydrazinolysis: (a) biantennary (80%), (b) biantennary with an intercalated N-acetylglucosamine residue (14%), and (c) triantennary (6%). Using concanavalin-A-affinity chromatography, native and S-carboxymethylated alpha 1--protease inhibitor were fractionated into three distinct molecular variants which were shown to contain only one type (a, b, or c, respectively) of glycan per molecule. This and previous observations on other serum glycoproteins support the proposal of uniformity of glycan type within individual molecular variants of glycoproteins.