Gonias S L, Balber A E, Hubbard W J, Pizzo S V
Biochem J. 1983 Jan 1;209(1):99-105. doi: 10.1042/bj2090099.
Rat alpha 1-macroglobulin (alpha 1M), rat alpha 2-macroglobulin (alpha 2M) migrated as single bands on non-denaturing gels when purified by the methods described. All three proteins demonstrated increased mobility after reaction with trypsin. A single saturable pathway rapidly cleared complexes of trypsin and the alpha-macroglobulins of mouse, rat and human from the circulation of mice. None of the native alpha-macroglobulins competed for clearance with the trypsin complexes. [14C]Methylamine incorporation was 4.1, 3.9, 2.6 and 3.2 mol/mol of proteinase inhibitor for human alpha 2M, rat alpha 1M, rat alpha 2M and mouse alpha 2M, respectively. Only rat alpha 2M, the acute-phase alpha-macroglobulin studied, showed no evidence of conformational change when subjected to electrophoresis after reaction with methylamine. The clearance of rat alpha 2M-methylamine was comparable with that of the native molecule. The other alpha-macroglobulin-methylamine complexes cleared faster than the inhibitors that had not reacted. Rat alpha 2M and rat alpha 2M-methylamine bound equivalent quantities of 1251-labelled trypsin (1.01 and 0.96 mol/mol respectively). The soya-bean trypsin inhibitor-resistant esterolytic activity of trypsin bound to rat alpha 2M-methylamine was approx. 90% suppressed compared with proteinase bound to native rat alpha 2M. This suppression was not due to a change in the affinity of soya-bean trypsin inhibitor for the complex. Reaction of rat alpha 2M-methylamine with trypsin resulted in a 'slow' to 'fast' electrophoretic conversion of the proteinase inhibitor, and exposure of the signal on the alpha 2M that causes the complex to clear from the murine circulation.
当按照所述方法纯化时，大鼠α1-巨球蛋白（α1M）、大鼠α2-巨球蛋白（α2M）在非变性凝胶上迁移为单一条带。与胰蛋白酶反应后，所有这三种蛋白质的迁移率均增加。一条单一的可饱和途径能迅速从小鼠循环中清除胰蛋白酶与小鼠、大鼠和人类α-巨球蛋白形成的复合物。天然的α-巨球蛋白均不与胰蛋白酶复合物竞争清除。对于人α2M、大鼠α1M、大鼠α2M和小鼠α2M，[14C]甲胺掺入量分别为每摩尔蛋白酶抑制剂4.1、3.9、2.6和3.2摩尔。在与甲胺反应后进行电泳时，只有所研究的急性期α-巨球蛋白大鼠α2M没有构象变化的迹象。大鼠α2M-甲胺的清除与天然分子相当。其他α-巨球蛋白-甲胺复合物的清除比未反应的抑制剂更快。大鼠α2M和大鼠α2M-甲胺结合等量的125I标记胰蛋白酶（分别为每摩尔1.01和0.96摩尔）。与结合天然大鼠α2M的蛋白酶相比，结合大鼠α2M-甲胺的胰蛋白酶对大豆胰蛋白酶抑制剂的抗酯解活性约被抑制90%。这种抑制不是由于大豆胰蛋白酶抑制剂对复合物亲和力的改变。大鼠α2M-甲胺与胰蛋白酶反应导致蛋白酶抑制剂从“慢”到“快”的电泳转变，并暴露了α2M上使复合物从小鼠循环中清除的信号。
