Farías R N, López Viñals A E, Posse E, Morero R D
Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (INSIBIO) (CONICET-UNT), San Miguel de Tucumán, Argentina.
Biochem J. 1989 Nov 15;264(1):285-7. doi: 10.1042/bj2640285.
Native insulin causes fusion of negatively charged liposomes in the pH range from 3.0 to 5.5. In marked contrast, insulin with all three amino groups succinylated did not show fusion ability at any pH. On the other hand, insulin amidated with glycine methyl ester with all six carboxyl groups blocked shifted its activity to higher pH, showing a pH range of activity from 3.0 to 7.4. When the carboxyl groups were recovered by hydrolysis of methoxyl groups from glycine methyl ester-treated insulin, the protein obtained (glycyl-insulin with six free carboxyl groups) behaved as native insulin. A good correlation between the isoelectric point values of insulin and its derivatives and their fusion properties was found.
天然胰岛素在pH值为3.0至5.5的范围内会导致带负电荷的脂质体融合。与之形成鲜明对比的是，所有三个氨基都被琥珀酰化的胰岛素在任何pH值下都没有显示出融合能力。另一方面，所有六个羧基都被甘氨酸甲酯封闭并酰胺化的胰岛素将其活性转移到更高的pH值，显示出3.0至7.4的活性pH范围。当通过从甘氨酸甲酯处理的胰岛素中水解甲氧基来恢复羧基时，得到的蛋白质（具有六个游离羧基的甘氨酰胰岛素）表现得与天然胰岛素一样。发现胰岛素及其衍生物的等电点值与其融合特性之间存在良好的相关性。
