Dodds A W, Law S K
University of Oxford, Department of Biochemistry, UK.
Immunol Rev. 1998 Dec;166:15-26. doi: 10.1111/j.1600-065x.1998.tb01249.x.
The complement system is an effector of both the acquired and innate immune systems of the higher vertebrates. It has been traced back at least as far as the echinoderms and so predates the appearance of the antibodies, T-cell receptors and MHC molecules of adaptive immunity. Central to the function of complement is the reaction of the thioester bond located within the structure of complement components C3 and C4. The structural thioester first appeared in a protease inhibitor, alpha 2-macroglobulin, in which it is involved in the immobilisation and entrapment of proteases. An important development in the C3 molecule has been the acquisition of a catalytic His residue which greatly increases the rate of reaction of the thioester with hydroxyl groups and with water.
补体系统是高等脊椎动物获得性免疫系统和先天性免疫系统的效应器。其起源至少可追溯到棘皮动物，因此早于适应性免疫的抗体、T细胞受体和MHC分子的出现。补体功能的核心是补体成分C3和C4结构中的硫酯键反应。结构硫酯最早出现在一种蛋白酶抑制剂α2-巨球蛋白中，它参与蛋白酶的固定和捕获。C3分子的一个重要发展是获得了一个催化性组氨酸残基，这大大提高了硫酯与羟基和水的反应速率。
