过氧化氢对铜锌超氧化物歧化酶结构损伤作用的进一步研究

我们曾观察到H_2O_2可使牦牛红细胞超氧化物歧化酶的活性下降及某些理化性质发生变化。在此基础上,进一步确证H_2O_2可使该酶结构受到损伤,其依据为H_2O_2作用后,酶的圆二色谱变化显示其β-折叠含量减少,无规则卷曲含量增加;酶分子中有二酪氨酸生成;组氨酸、精氨酸、赖氨酸、丝氨酸和苏氨酸含量相对减少,而天冬氨酸、谷氨酸和甘氨酸含量相对增加;用2.4-二硝基苯肼试剂可测得羰基生成;SDS-PAGE测出酶的部分亚基被降解为小肽段;用荧光胺法测得自由氨基量的增加。本文对上述变化的机理进行了探讨。

Further Study on the Structure of Damage of Yak Erythrocyte Superoxide Dismutase by Hrdregen Peroxide

After yak erythrocyte superoxide dismutase (SOD) was treated with H_2O_2, the following results were obtained. 1. The percentage of β-sheet decreased whereas that of random coil increased in spite of no change of α-helix as assessed by circular dichroism. 2. The production of bityrosine was observed. 3. Amino acid analysis showed that there was a substantial decrease in the content of histindine, arginine, lysine, serine and threonine residues, and a significant increase in the content of aspartic acid, glutamic acid and glycine. 4. Carbonyl groups were generated from the treated SOD 5. SOD degraded to fragments was detected by both SDS-PAGE and fluorescamine test. The fragmentation of SOD was accompanied with an apparent increase in free amino groups, showing that the fragmentation was caused by peptide bond hydrolysis rather than by some other form of chain scission. These results showed that the structure of SOD was extensively modified by H_2O_2. Its mechanism was discussed.