Immunoglobulin A (IgA) proteinase from Clostridium ramosum is the enzyme which cleaves IgA of both subclasses; in contrast, the other bacterial proteinases cleave only IgA1 proteins. Previous reports characterized the activity of proteinase naturally secreted by C. ramosum specific for the normal human serum IgA of IgA1 and IgA2m(1) subclasses and also for secretory IgA (SIgA). Its amino acid sequence was determined, and the recombinant proteinase which cleaved IgA of both subclasses was prepared. Here we report the optimized expression, purification, storage conditions and activity testing against purified human milk SIgA. The recombinant C. ramosum IgA proteinase isolated in the high degree of purity exhibited almost complete cleavage of SIgA of both subclasses. The proteinase remained active upon storage for more than 10 month at −20 °C without substantial loss of enzymatic activity. Purified SIgA fragments are suitable for studies of all antigen-binding and Fc-dependent functions of SIgA involved in the protection against infections with mucosal pathogens.

来自Clostridium ramosum 的免疫球蛋白 A (IgA) 蛋白酶是裂解两个亚类 IgA 的酶；相比之下，其他细菌蛋白酶只切割 IgA1 蛋白。以前的报告描述了由C. ramosum自然分泌的蛋白酶的活性，这些蛋白酶对 IgA1 和 IgA2m(1) 亚类的正常人血清 IgA 以及分泌型 IgA (SIgA) 具有特异性。确定了其氨基酸序列，制备了裂解两个亚类IgA的重组蛋白酶。在这里，我们报告了针对纯化人乳 SIgA 的优化表达、纯化、储存条件和活性测试。重组C. ramosum以高纯度分离的 IgA 蛋白酶表现出几乎完全切割两个亚类的 SIgA。蛋白酶在 -20 °C 下储存超过 10 个月后仍保持活性，而酶活性没有显着损失。纯化的 SIgA 片段适用于研究 SIgA 的所有抗原结合和 Fc 依赖性功能，这些功能涉及防止粘膜病原体感染。