Mulks M H, Kornfeld S J, Frangione B, Plaut A G
J Infect Dis. 1982 Aug;146(2):266-74. doi: 10.1093/infdis/146.2.266.
Haemophilus influenzae is one of five bacterial species known to produce IgA proteases, enzymes that specifically cleave the human IgA1 heavy chain. Strains of H. influenzae produce three distinct types of IgA proteases that cleave different peptide bonds within the IgA1 hinge region. Type 1 protease cleaves the prolyl-seryl bond at position 231-232; type 2 protease cleaves the prolyl-threonyl bond at position 235-236, the same bond attacked by Neisseria gonorrhoeae and Neisseria meningitidis type 2 proteases. Type 3 protease yields a unique double Fd cleavage pattern; the exact peptide bonds cleaved have not been determined. The type of protease produced correlates with the serotype, but not with the biotype, of the isolate; serotypes A, B, D, and F produce primarily type 1 protease, whereas serotypes C and E produce only type 2 enzyme. Each nontypable strain yields one of the three protease types. These data further extend our knowledge of the extreme specificity of the IgA proteases and suggest that IgA protease type may be useful in the taxonomy and epidemiology of H. influenzae.
流感嗜血杆菌是已知能产生IgA蛋白酶的五种细菌之一，IgA蛋白酶是一种能特异性切割人IgA1重链的酶。流感嗜血杆菌菌株产生三种不同类型的IgA蛋白酶，它们能切割IgA1铰链区内不同的肽键。1型蛋白酶切割231 - 232位的脯氨酰 - 丝氨酰键；2型蛋白酶切割235 - 236位的脯氨酰 - 苏氨酰键，这也是淋病奈瑟菌和脑膜炎奈瑟菌2型蛋白酶攻击的相同肽键。3型蛋白酶产生独特的双Fd切割模式；确切切割的肽键尚未确定。所产生的蛋白酶类型与分离株的血清型相关，但与生物型无关；血清型A、B、D和F主要产生1型蛋白酶，而血清型C和E仅产生2型酶。每个不可分型菌株产生三种蛋白酶类型中的一种。这些数据进一步扩展了我们对IgA蛋白酶极端特异性的认识，并表明IgA蛋白酶类型可能在流感嗜血杆菌的分类学和流行病学中有用。
