Gagnon J
Philos Trans R Soc Lond B Biol Sci. 1984 Sep 6;306(1129):301-9. doi: 10.1098/rstb.1984.0091.
The activation of complement is initiated by two independent pathways. Each leads to the formation of a complex protease, C3 convertase, with equivalent specificity and function but different composition. The convertase derived from the classical pathway is composed of complement components C4 and C2 while that from the alternative pathway consists of components C3 and Factor B. C2 and Factor B contain the catalytic site of each convertase respectively. The amino acid sequence of Factor B has been determined. Limited sequence of CNBr-peptides isolated from C2 has also been obtained. The two enzymes are shown to be homologous and to represent a novel type of serine proteinase, characterized by their unusual structure and mechanism of activation, when compared to known serine proteinases.
补体的激活由两条独立的途径启动。每一条途径都会导致形成一种具有同等特异性和功能但组成不同的复合蛋白酶——C3转化酶。源自经典途径的转化酶由补体成分C4和C2组成，而源自替代途径的转化酶由成分C3和B因子组成。C2和B因子分别含有各转化酶的催化位点。B因子的氨基酸序列已被确定。从C2分离得到的CNBr肽段的有限序列也已获得。与已知的丝氨酸蛋白酶相比，这两种酶显示出同源性，并代表一种新型的丝氨酸蛋白酶，其特点是具有不寻常的结构和激活机制。
