Gliemann J, Sottrup-Jensen L
FEBS Lett. 1987 Aug 31;221(1):55-60. doi: 10.1016/0014-5793(87)80351-4.
The cellular binding and uptake was studied for alpha 1-inhibitor3, a monomeric 200 kDa proteinase inhibitor present in rat plasma. After intravenous injection in the rat the inhibitor disappeared from the circulation with a half-time of 2.5 min when complexed with chymotrypsin, whereas the half-time for uncomplexed inhibitor was more than 60 min. 6 min after the injection of labelled complex, 83% was in the liver and 2.5% in the spleen. In vitro experiments at 4 degrees C with isolated hepatocytes and peritoneal macrophages showed binding to the previously described receptors which bind and internalize the tetrameric rat and human alpha 2-macroglobulin-proteinase complexes. The binding affinities were similar for the two types of complexes and binding was followed by uptake and degradation of the labelled complex when the cells were warmed to 37 degrees C. The binding of uncomplexed alpha 1-inhibitor3 was low and did not increase following treatment with methylamine in spite of cleavage of the internal thiol ester. alpha 1-Inhibitor3-methylamine was changed to the receptor binding form when treated with chymotrypsin which caused the cleavage of at least one peptide bond in the bait region.
对α1 - 抑制因子3进行了细胞结合和摄取研究，它是一种存在于大鼠血浆中的200 kDa单体蛋白酶抑制剂。在大鼠静脉注射后，与胰凝乳蛋白酶结合的抑制剂从循环中消失的半衰期为2.5分钟，而未结合的抑制剂半衰期超过60分钟。注射标记复合物6分钟后，83%在肝脏中，2.5%在脾脏中。在4℃下用分离的肝细胞和腹膜巨噬细胞进行的体外实验表明，其与先前描述的能结合并内化四聚体大鼠和人α2 - 巨球蛋白 - 蛋白酶复合物的受体发生结合。两种复合物的结合亲和力相似，当细胞升温至37℃时，结合后会摄取并降解标记复合物。未结合的α1 - 抑制因子3的结合率较低，用甲胺处理后，尽管内部硫酯被裂解，但结合率并未增加。用胰凝乳蛋白酶处理α1 - 抑制因子3 - 甲胺时，它会转变为受体结合形式，这会导致诱饵区域至少一个肽键的裂解。
