Glaser C B, Karic L, Fallat R J, Stockert R
Biochim Biophys Acta. 1977 Nov 25;495(1):87-92. doi: 10.1016/0005-2795(77)90242-2.
Alpha-1-antitrypsin from normal individuals (Pi type MM) from those with an inherited deficiency of circulatory protein (Pi type ZZ) were labelled with 125I and plasma clearance rates measured in rats either prior to, or following treatment with neuraminidase to remove terminal sialic acid residues. In addition, these proteins and the derivatives were tested for their ability to bind to an hepatic binding protein obtained from rabbit liver membranes that has been shown to be responsible for the clearance of serum asialoglycoproteins. Finally, the two native forms of alpha-1-antitrypsin were treated with galactose oxidase followed by reduction with tritiated potassium borohydride and then analyzed for tritium incorporation in the neutral sugar fraction. The results indicate: (a) clearance from plasma for both forms of alpha-1-antitrypsin is dramatically enhanced upon the loss of terminal sialic acid residues to the liver membrane protein; (b) Z protein does not exhibit terminal galactosyl residues; (c) the low level of Z protein in plasma cannot be accounted for by a faster rate of clearance relative to M protein. The relevance of these findings to the alpha-1-antitrypsin deficiency state are discussed.
将来自正常个体（Pi型MM）和遗传性循环蛋白缺乏个体（Pi型ZZ）的α-1-抗胰蛋白酶用¹²⁵I标记，并在大鼠中测量其血浆清除率，测量时间为用神经氨酸酶处理以去除末端唾液酸残基之前或之后。此外，检测这些蛋白质及其衍生物与从兔肝细胞膜获得的肝结合蛋白结合的能力，该肝结合蛋白已被证明负责血清去唾液酸糖蛋白的清除。最后，将两种天然形式的α-1-抗胰蛋白酶用半乳糖氧化酶处理，然后用氚化硼氢化钾还原，接着分析中性糖部分中氚的掺入情况。结果表明：（a）两种形式的α-1-抗胰蛋白酶在失去末端唾液酸残基后，从血浆中的清除率显著提高至肝膜蛋白；（b）Z蛋白不显示末端半乳糖基残基；（c）血浆中Z蛋白水平低不能用相对于M蛋白更快的清除率来解释。讨论了这些发现与α-1-抗胰蛋白酶缺乏状态的相关性。
