Locations of oligosaccharide chains in human alpha 1-protease inhibitor and oligosaccharide structures at each site.

Previous studies in this laboratory had shown that the alpha 1-protease inhibitor (alpha 1-PI) molecule contained two types of oligosaccharides, biantennary and triantennary. Cleavage of human alpha 1-protease inhibitor with CNBr resulted in three carbohydrate-containing fragments, I-III. Composition data revealed that each of these CNBr fragments contained one oligosaccharide chain. The oligosaccharide structure at each glycosylation site on each purified CNBr fragment was determined by compositional analysis, behavior on Con A affinity chromatography, and methylation analysis. From the results of these studies, we propose that fragment I contains one carbohydrate chain that can be of either the biantennary or triantennary type. On the other hand, fragments II and III each contain one carbohydrate chain exclusively by the biantennary type of complex N-glycoside.