Müller-Eberhard H J, Polley M J, Calcott M A
J Exp Med. 1967 Feb 1;125(2):359-80. doi: 10.1084/jem.125.2.359.
A functional unit of the human complement system has been delineated. It is composed of two subunits which are derived from the second (C'2) and from the fourth (C'4) component of complement. Purified C'2 and C'4 were found to interact in free solution and to form a reversible protein-protein complex. When acted upon by C'1 esterase in the presence of Mg ions, the reversible complex acquires stability and the ability to act enzymatically on the third component of complement. The trivial name C'3 convertase has been selected to denote the enzyme. Molecular weight determinations suggest that the entire C'4 molecule, but probably only a fragment of the C'2 molecule, are incorporated into C'3 convertase. Prior treatment of C'2 with iodine led to enhanced stability and activity of the enzyme. It was shown that the cell-bound form of C'3 convertase is cytolytically active and that the free enzyme is able to induce lysis from the fluid phase of erythrocytes from patients with paroxysmal nocturnal hemoglobinuria. Evidence was presented that action of C'3 convertase on C'3 results in fragmentation of the molecule.
人类补体系统的一个功能单位已被阐明。它由两个亚基组成，这两个亚基分别来自补体的第二成分（C'2）和第四成分（C'4）。已发现纯化的C'2和C'4在自由溶液中相互作用并形成可逆的蛋白质-蛋白质复合物。当在镁离子存在下受到C'1酯酶作用时，该可逆复合物获得稳定性并具有对补体第三成分进行酶促作用的能力。已选用俗名C'3转化酶来表示该酶。分子量测定表明，整个C'4分子，但可能只有C'2分子的一个片段，被纳入C'3转化酶中。用碘预先处理C'2可提高该酶的稳定性和活性。结果表明，细胞结合形式的C'3转化酶具有溶细胞活性，而游离酶能够从阵发性夜间血红蛋白尿患者的红细胞液相中诱导细胞溶解。有证据表明，C'3转化酶对C'3的作用导致该分子断裂。
