Mega T, Lujan E, Yoshida A
J Biol Chem. 1980 May 10;255(9):4057-61.
Human alpha 1-protease inhibitor has three oligosaccharide side chains attached to 3 separate asparaginyl residues of the protein by N-glycosyl linkages. Two of the three asparaginyl residues link mostly to the A-type oligosaccharide chains which consist of Man3, Gal2, (GlcNAc)4 and (NeuAc)2. One of the three asparaginyl residues also attaches to a B-type oligosaccharide chain, which consists of Man3, Gal3, (GlcNAc)5, and (NeuAc)3. The ratio of A-chain to B-chain in this particular position is about 2:1. The structures of A- and B-chains of the glycoprotein were examined by periodate oxidation, sequential glycosidase digestion, and permethylation. The results unequivocally revealed the following structure for A-chains. (Formula: see text). B-type oligosaccharide chains have an additional trisaccharide, i.e. NeuAc 2 alpha leads to 3 Gal 1 beta leads to 4 GlcNAc attached to mannose at the (a) and/or (b) position of A-type chains by a beta 1 leads to 4 linkage. The sialic acid of human alpha 1-protease inhibitor was determined to be N-acetylneuraminic acid.
人α1-蛋白酶抑制剂有三条寡糖侧链，通过N-糖基键与该蛋白质的3个不同天冬酰胺残基相连。三个天冬酰胺残基中的两个主要连接到A型寡糖链上，A型寡糖链由甘露糖3、半乳糖2、（N-乙酰葡糖胺）4和（N-乙酰神经氨酸）2组成。三个天冬酰胺残基中的一个还连接到一条B型寡糖链上，该B型寡糖链由甘露糖3、半乳糖3、（N-乙酰葡糖胺）5和（N-乙酰神经氨酸）3组成。在这个特定位置上A链与B链的比例约为2:1。通过高碘酸氧化、顺序糖苷酶消化和全甲基化研究了该糖蛋白A链和B链的结构。结果明确揭示了A链的以下结构。（分子式：见正文）。B型寡糖链有一个额外的三糖，即N-乙酰神经氨酸2α→3半乳糖1β→4 N-乙酰葡糖胺，通过β1→4键连接到A型链（a）和/或（b）位置的甘露糖上。人α1-蛋白酶抑制剂的唾液酸被确定为N-乙酰神经氨酸。
