Prahl J W
Biochem J. 1967 Aug;104(2):647-55. doi: 10.1042/bj1040647.
The digestion of the Fc fragment of rabbit immunoglobulin IgG by several proteolytic enzymes was investigated by using gel filtration and starch-gel electrophoresis in 8m-urea-formate as criteria of the extent of degradation. Though fragment Fc and mildly reduced fragment Fc proved resistant to tryptic hydrolysis, papain and pepsin cleaved the fragment at acidic pH values and appeared to give rise to a similar spectrum of products. A (limit) peptide comprising the C-terminal 113 residues of the heavy chain was isolated and identified from the pepsin-digest products of fragment Fc. The products of proteolytic digestion of fragment Fc were no longer able to inhibit passive cutaneous anaphylaxis by rabbit anti-(bovine serum albumin) or demonstrate reversed passive cutaneous anaphylaxis in the guinea pig. Nor were they able to inhibit the intestinal absorption of heterologous immunoglobulin IgG in the young mouse. These studies imply that the site or sites responsible for these biological properties of intact fragment Fc reside in the N-terminal 30-40% of the fragment.
通过使用凝胶过滤和在8m-尿素甲酸盐中的淀粉凝胶电泳作为降解程度的标准，研究了几种蛋白水解酶对兔免疫球蛋白IgG的Fc片段的消化作用。尽管Fc片段和轻度还原的Fc片段被证明对胰蛋白酶水解具有抗性，但木瓜蛋白酶和胃蛋白酶在酸性pH值下切割该片段，并且似乎产生了类似的产物谱。从Fc片段的胃蛋白酶消化产物中分离并鉴定了一种包含重链C末端113个残基的（极限）肽。Fc片段的蛋白水解消化产物不再能够抑制兔抗（牛血清白蛋白）的被动皮肤过敏反应，也不能在豚鼠中表现出反向被动皮肤过敏反应。它们也不能抑制幼鼠中异源免疫球蛋白IgG的肠道吸收。这些研究表明，负责完整Fc片段这些生物学特性的一个或多个位点位于该片段的N末端30-40%。
