Wie S I, Dorrington K J, Froese A
J Immunol. 1978 Jul;121(1):98-104.
Bovine colostral IgG1 was subjected to both papain and pepsin hydrolysis. Papain digestion appeared to be optimal at pH 7.4 in the presence of 0.01 M cysteine. The molecule was split at the COOH-terminal side of the interchain disulfide bond(s), and in addition to Fab fragments, two Fc fragments, designated Fc(I) and Fc(II), were obtained. Both Fc fragments had an identical NH2-terminal sequence, but differed in m.w. by about 10,000, with Fc(II) being the smaller one. Differences were also observed in their circular dichroism (CD) spectra and in their susceptibility to carboxypeptidase hydrolysis. These results suggested that the distinguishing characteristics of the two Fc fragments resided in the COOH-terminal parts of the molecules. Pepsin hydrolysis yielded the expected F(ab')2 and pFc' fragments. This hydrolysis was found to be dependent upon substrate concentration leading to aggregate formation at IgG1 concentrations below 3%.
牛初乳IgG1分别用木瓜蛋白酶和胃蛋白酶进行水解。在0.01 M半胱氨酸存在的情况下，木瓜蛋白酶消化在pH 7.4时似乎最为适宜。该分子在链间二硫键的COOH末端一侧被裂解，除了Fab片段外，还获得了两个Fc片段，分别命名为Fc(I)和Fc(II)。两个Fc片段具有相同的NH2末端序列，但分子量相差约10,000，其中Fc(II)较小。在它们的圆二色性（CD）光谱以及对羧肽酶水解的敏感性方面也观察到差异。这些结果表明，两个Fc片段的显著特征存在于分子的COOH末端部分。胃蛋白酶水解产生了预期的F(ab')2和pFc'片段。发现这种水解依赖于底物浓度，在IgG1浓度低于3%时会导致聚集体形成。
