N-linked neutral sugar chains of aminopeptidase N purified from rat small intestinal brush-border membrane

Neutral oligosaccharides, which accounted for 74% of the total N-linked sugar chains released by hydrazinolysis of rat small intestinal aminopeptidase N, were investigated on a structural basis. They are mainly composed of complex-type sugar chains with tri- and tetraantennary structures, and small amounts of high mannose type sugar chains (7% of the total neutral sugar chains) are also included. The unique feature of the complex-type sugar chains is the most of them contain terminal N-acetylglucosamine residues and blood group H antigenic determinants in their outer chain moieties, and bisecting N-acetylglucosamine residues in their trimannosyl cores. Both the type 1H and type 2H determinants are found, but the former is mainly expressed at the distal portions of the outer chain moieties of the oligosaccharides.