Hill B C, Greenwood C
FEBS Lett. 1984 Jan 30;166(2):362-6. doi: 10.1016/0014-5793(84)80113-1.
The reaction with O2 of equimolar mixtures of cytochrome c and cytochrome c oxidase in high and low ionic strength buffers has been examined by flow-flash spectrophotometry at room temperature. In low ionic strength media where cytochrome c and the oxidase are bound in an electrostatic, 1:1 complex some of the cytochrome c is oxidised at a faster rate than a metal centre of the oxidase. In contrast, when cytochrome c and cytochrome c oxidase are predominantly dissociated at high ionic strength cytochrome c oxidation occurs only slowly (t1/2 = 5 s) following the complete oxidation of the oxidase. These results demonstrate that maximal rates of electron transfer from cytochrome c to O2 occur when both substrates are present on the enzyme. The heterogeneous oxidation of cytochrome c observed in the complex implies more than one route for electron transfer within the enzyme. Possibilities for new electron transfer pathways from cytochrome c to O2 are proposed.
在室温下，通过流动闪光分光光度法研究了细胞色素c和细胞色素c氧化酶的等摩尔混合物在高离子强度和低离子强度缓冲液中与O2的反应。在低离子强度介质中，细胞色素c和氧化酶以静电1:1复合物形式结合，部分细胞色素c的氧化速率比氧化酶的金属中心更快。相比之下，当细胞色素c和细胞色素c氧化酶在高离子强度下主要解离时，细胞色素c的氧化仅在氧化酶完全氧化后缓慢发生（t1/2 = 5秒）。这些结果表明，当两种底物都存在于酶上时，从细胞色素c到O2的电子转移速率最大。在复合物中观察到的细胞色素c的异质氧化意味着酶内电子转移有不止一条途径。提出了从细胞色素c到O2的新电子转移途径的可能性。
