活性氧所致超氧化物歧化酶肽链断裂的观察

探究活性氧所致铜锌超氧化物歧化酶（ＳＯＤ）肽链断裂的情况。将过氧化氢或抗坏血酸－Ｆｅ（Ⅲ）分别作用于马来酰亚胺标记的ＳＯＤ，然后用高效液相反相色谱（ＲＰＨＰＬＣ）分析，经１ｍｍｏｌ／ＬＨ２Ｏ２处理后ＳＯＤ用ＲＰ－ＨＰＬＣ分离出二个肽段，用顺磁共振检测显示只有一个肽段具有马来酰亚胺信号，经５ｍｍｏｌ／ＬＨ２Ｏ２处理后ＳＯＤ有四个肽段生成，其中有一个肽段具有马来酰亚胺信号，用５ｍｍｏｌ／Ｌ抗坏血酸和０．０１ｍｍｏｌ／ＬＦｅＣｌ３处理后ＳＯＤ有三个肽段生成，用５０ｍｍｏｌ／Ｌ抗坏血酸及１．０ｍｍｏｌ／ＬＦｅＣｌ３处理后ＳＯＤ也产生相同的三个肽段，只是肽段的量多．结果提示Ｈ２Ｏ２所致ＳＯＤ肽链断裂无“定点”现象，而抗坏血酸－Ｆｅ（Ⅲ）所致ＳＯＤ肽链断裂呈“定点”断裂。

Observation of the Superoxide Dismutase Fragmentation by Reactive Oxygen Species

Exposure of bovine erythrocyte cupro-zinc superoxide dismutase (SOD) to H2O2 or ascorbate-Fe (Ⅲ) gave rise to the chain breaks of the enzyme labelled with maleimido.Two or four peptides were isolated from lmmol/L or 5mmol/L H2O2 treated-SOD by reversed phase high performance liquid chromatography (HPLC), and only one peptide in each case showed the signal of maleimido detected by electron spin resonance.Three peptides were isolated from 5mmol/L ascorbate and 0.01 mmol/L FeCl3 or 50mmol/L ascorbate and 1mmol/L FeCl3 treated-SOD and one peptide in each case showed the signal of maleimide. The results indicated that 1mmol/L or 5mmol/L H2O2 caused one site or two sites breaks at the peptide chain of SOD, and ascorbate-Fe (Ⅲ) caused two.sites breaks. It is suggested that site-specific chain breaks might be caused by ascorbate-Fe (Ⅲ), but not by H2O2.