Liposome-assisted activity of superoxide dismutase under oxidative stress
Liposome-assisted activity of superoxide dismutase under oxidative stress
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DOI：
10.1263/jbb.99.423
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发表时间：
2005-04-01
影响因子：
2.8
通讯作者：
Kuboi, R
中科院分区：
文献类型：
--
作者：
Nagami, H;Yoshimoto, N;Kuboi, R
生物膜是细胞抵御各种环境应激（如热和活性氧（ROS））的最前线，并且预计在具有抗氧化酶的抗氧化系统中发挥重要作用，类似于其与热休克蛋白合作的伴侣样功能。研究了在人工膜-脂质体存在下超氧化物歧化酶（SOD）催化O-2（-）歧化为H_2O_2的氧化应激反应，以获得生物活性氧清除系统的基础信息。SOD在H_2O存在下失去活性，并被发现有两个环，其中一个环包含一个α-螺旋，该螺旋将底物O-2（-）呈递到SOD的活性中心（Cu（II））。圆二色性分析表明，在H_2O_2存在下，SOD的α-螺旋环的含量随着SOD的失活和构象变化而减少，表明α-螺旋环的构象影响SOD的活性。在由1-棕榈酰-2-油酰-SN-甘油-3-磷酸胆碱（POPC）组成的脂质体存在下，尽管SOD的a-螺旋结构含量减少，但在H2 O2存在下，SOD并未被灭活。利用介电色散分析发现氧化的SOD在氧化应激下与脂质体表面相互作用。基于这些结果，提出了脂质体上SOD保护ROS的可能机制。
A biological membrane is the front line of defense for cells against various environmental stresses such as heat and reactive oxygen species (ROS) and is expected to play an important role in the antioxidant system with antioxidant enzymes, similarly to its chaperone-like function in cooperation with heat shock proteins. The oxidative stress response of superoxide dismutase (SOD), which is known to catalyze the dismutation of O-2(-) to H2O2 was investigated in the presence of artificial membranes, liposomes, in order to obtain fundamental information on the biological ROS scavenging system. SOD lost its activity in the presence of H2O, and was found to have two loops including one which contains an a-helix which presents the substrate O-2(-) to the activity center of SOD (Cu(II)). From circular dichroism analysis of SOD in the presence of H2O2, the contents of the a-helix in SOD were found to decrease in correspondence with the inactivation and conformational change of SOD, suggesting that the conformation of the a-helix loops affects SOD activity. In the presence of liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), SOD was not inactivated in the presence of H2O2 although the contents of its a-helix structure were decreased. The oxidized SOD was found to interact with the liposome surface under oxidative stress using dielectric dispersion analysis. Based on these results, a possible mechanism of SOD protection against ROS on liposomes was presented.