Electron spin resonance investigation of the cyanyl and azidyl radical formation by cytochrome c oxidase
Electron spin resonance investigation of the cyanyl and azidyl radical formation by cytochrome c oxidase
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DOI：
10.1074/jbc.274.35.24611
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发表时间：
1999-08-27
影响因子：
4.8
通讯作者：
Mason, RP
中科院分区：
文献类型：
--
作者：
Chen, YR;Sturgeon, BE;Mason, RP
氰化物（CN-）是一种常用的线粒体呼吸抑制剂，它与细胞色素c氧化酶（CcO）的亚铁血红素a（3）结合，CcO氧化氰化物生成氰自由基（（CN）-C-）。使用ESR自旋捕获技术，检测到5，5-二甲基-1-吡咯啉N-氧化物（DMPO）/（CN）-C-。自由基加合物，CcO将氰化物酶促转化为氰酰基自由基是时间依赖性的，但不受叠氮化物（N-3（-））的影响。在分离的CcO中存在的少量但可变量的化合物P解释了氰化物到氰酰基自由基的这种单电子氧化。相反，分离的CcO表现出很少的催化叠氮化物氧化的能力，可能是因为叠氮化物对CcO的亲和力较低。然而，DMPO/N-. (3)自由基加合物很容易检测时，H2 O2包括在系统中。这里提出的结果表明，需要重新评估氧化应激在线粒体的氰化物或叠氮化物引起的“化学缺氧”，以解释高活性自由基的存在。
Cyanide (CN-) is a frequently used inhibitor of mitochondrial respiration due to its binding to the ferric heme a(3) of cytochrome c oxidase (CcO), As-isolated CcO oxidized cyanide to the cyanyl radical ((CN)-C-.) that was detected, using the ESR spin-trapping technique, as the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)/(CN)-C-. radical adduct, The enzymatic conversion of cyanide to the cyanyl radical by CcO was time-dependent but not affected by azide (N-3(-)), The small but variable amounts of compound P present in the as-isolated CcO accounted for this one-electron oxidation of cyanide to the cyanyl radical, In contrast, as-isolated CcO exhibited little ability to catalyze the oxidation of azide, presumably because of azide's lower affinity for the CcO. However, the DMPO/N-.(3) radical adduct was readily detected when H2O2 was included in the system. The results presented here indicate the need to re-evaluate oxidative stress in mitochondria "chemical hypoxia" induced by cyanide or azide to account for the presence of highly reactive free radicals.