Kilian M, Mestecky J, Kulhavy R, Tomana M, Butler W T
J Immunol. 1980 Jun;124(6):2596-600.
IgA1 proteases from H. influenzae, N. meningitidis, S. pneumoniae, and S. sanguis were compared with respect to site of cleavage in the IgA1 molecule and EDTA sensitivity. Proteases from S. sanguis and S. pneumoniae cleaved the Pro (227)-Thr (228) bond within the hinge region of the alpha 1 chain and were inhibited by EDTA. H. influenzae IgA1 protease cleaved the Pro (231)-Ser (232) peptide bond. The activity of IgA1 proteases from H. influenzae and N. meningitidis was unaffected by EDTA. Purified and denatured alpha 1 chain was cleaved only in the hinge region. Other component chains of secretory IgA (secretory component, light and J chains) were not susceptible. In addition to IgA1 protease, S. pneumoniae released exo- and endoglycosidases that removed a considerable portion of carbohydrate side chains of IgA1; this activity was absent from crude IgA1 protease preparations of the other three bacterial species. Association in vitro of polymeric IgA1 with SC did not inhibit the degradation of IgA1 proteases. The considerable resistance of secretory IgA to cleavage by IgA1 proteases may be explained in part by the presence of IgA1 protease-neutralizing antibodies in secretory IgA.
对来自流感嗜血杆菌、脑膜炎奈瑟菌、肺炎链球菌和血链球菌的IgA1蛋白酶在IgA1分子中的切割位点和对EDTA的敏感性方面进行了比较。血链球菌和肺炎链球菌的蛋白酶切割α1链铰链区内的Pro(227)-Thr(228)键，并被EDTA抑制。流感嗜血杆菌IgA1蛋白酶切割Pro(231)-Ser(232)肽键。流感嗜血杆菌和脑膜炎奈瑟菌的IgA1蛋白酶活性不受EDTA影响。纯化和变性的α1链仅在铰链区被切割。分泌型IgA的其他组成链（分泌成分、轻链和J链）不易被切割。除了IgA1蛋白酶外，肺炎链球菌还释放外切糖苷酶和内切糖苷酶，这些酶去除了IgA1相当一部分碳水化合物侧链；其他三种细菌的粗制IgA1蛋白酶制剂中没有这种活性。聚合IgA1与SC在体外的结合并不抑制IgA1蛋白酶的降解。分泌型IgA对IgA1蛋白酶切割具有相当的抗性，这可能部分是由于分泌型IgA中存在IgA1蛋白酶中和抗体。
