Molla A, Kagimoto T, Maeda H
Department of Microbiology, Kumamoto University Medical School, Japan.
Infect Immun. 1988 Apr;56(4):916-20. doi: 10.1128/iai.56.4.916-920.1988.
Seven clinical and two nonclinical isolates of Serratia marcescens were examined for their ability to produce extracellular enzymes that cleave immunoglobulin G (IgG) and IgA molecules. All seven clinical isolates excreted a large amount of a 56-kilodalton (kDa) protease (56K protease) and small amounts of a 60-kDa and a 73-kDa protease (60K and 73K proteases, respectively) in culture medium during growth. All purified proteases cleaved IgG and IgA effectively if the level of protease production exceeded 2 to 5 micrograms/ml. The proteolytic activity in the culture supernatant was inhibited by about 85% by a chelating agent (EDTA), which indicated that the major immunoglobulin-cleaving enzyme is the metalloprotease(s) reported previously. Immunological quantification of proteases by single radial immunodiffusion showed similar results: the amount of 56K protease was about 65% and those of the 60K and 73K proteases were about 20 and 5%, respectively. Incubation for 3 h at 37 degrees C was required to generate immunoreactive Fab and Fc fragments. Further analysis of the cleavage products of IgG or IgA demonstrated that the 56K protease, as well as the 60K and 73K proteases, cleaves only the heavy chain of these immunoglobulins near the hinge region to generate Fab and Fc fragments. The susceptibilities of the subclasses of IgG and IgA to the 56K protease were as follows: IgG3 greater than IgG1 greater than IgG2 greater than IgG4 and IgA1 greater than IgA2. IgG2, IgG4, and IgA2 were relatively resistant to the 56K protease.
对七株临床分离株和两株非临床分离株的粘质沙雷氏菌进行了检测，以评估它们产生能裂解免疫球蛋白G（IgG）和IgA分子的细胞外酶的能力。所有七株临床分离株在生长过程中均在培养基中分泌大量56千道尔顿（kDa）的蛋白酶（56K蛋白酶）以及少量60kDa和73kDa的蛋白酶（分别为60K和73K蛋白酶）。如果蛋白酶的产生水平超过2至5微克/毫升，所有纯化的蛋白酶都能有效裂解IgG和IgA。培养上清液中的蛋白水解活性被螯合剂（EDTA）抑制了约85%，这表明主要的免疫球蛋白裂解酶是先前报道的金属蛋白酶。通过单向放射免疫扩散对蛋白酶进行免疫定量分析得到了类似的结果：56K蛋白酶的量约为65%，60K和73K蛋白酶的量分别约为20%和5%。需要在37℃下孵育3小时才能产生具有免疫反应性的Fab和Fc片段。对IgG或IgA裂解产物的进一步分析表明，56K蛋白酶以及60K和73K蛋白酶仅在铰链区附近裂解这些免疫球蛋白的重链，以产生Fab和Fc片段。IgG和IgA亚类对56K蛋白酶的敏感性如下：IgG3＞IgG1＞IgG2＞IgG4和IgA1＞IgA2。IgG2、IgG4和IgA2对56K蛋白酶相对耐药。
