Proton involvement in the transition from the "peroxy" to the ferryl intermediate of cytochrome c oxidase.
Proton involvement in the transition from the "peroxy" to the ferryl intermediate of cytochrome c oxidase.
复制标题
质子参与细胞色素c氧化酶从“过氧”到ferryl中间体的转变。
DOI：
10.1021/bi002373i
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发表时间：
2001
期刊：
影响因子：
2.9
通讯作者：
Palmer,G
中科院分区：
文献类型：
--
作者：
Fabian,M;Palmer,G
在没有任何外部电子供体的情况下，细胞色素氧化酶（CcO-607）的“过氧”中间体转化为铁酰基形式（CcO-580），随后转化为氧化酶。CcO-607转化为CcO-580形式的速率在pH 3.0和pH 7.6之间具有pH依赖性。该转化速率常数的对数曲线是pH的线性函数，斜率为-0.92，这意味着在跃迁中涉及单个质子。在将pH从8.1快速降低至5.8时，通过直接pH测量观察到一个质子的吸收，并且质子吸收的动力学与CcO-607至CcO-580的光谱转换一致。我们解释的CcO-607 CcO-580的缓慢内源性衰变的质子转移到一个去质子化的基团产生的双核腔在CcO-607形成的结果。该基团不能自由地与来自培养基的质子接触，其pKais可能高于9.0。
In the absence of any external electron donor, the “peroxy” intermediate of cytochromecoxidase (CcO-607) is converted to the ferryl form (CcO-580) and subsequently to oxidized enzyme. The rate of conversion of CcO-607 to the CcO-580 form is pH dependent between pH 3.0 and pH 7.6. A plot of the logarithm of the rate constant for this conversion is a linear function of pH with a slope of −0.92, implying the involvement of a single proton in the transition. Upon rapidly lowering the pH from 8.1 to 5.8, the uptake of one proton was observed by direct pH measurement, and the kinetics of proton uptake coincide with the spectral conversion of CcO-607 to CcO-580. We interpret the slow endogenous decay of CcO-607 to CcO-580 to be the result of proton transfer to a deprotonated group generated in the binuclear cavity during CcO-607 formation. This group is not freely accessible to protons from the medium, and its pKais probably higher than 9.0.