Boelens R, Wever R
Biochim Biophys Acta. 1979 Aug 14;547(2):296-310. doi: 10.1016/0005-2728(79)90012-4.
Under continuous illumination the CO binding curve of reduced carboxy-cytochrome c oxidase maintains the shape of the binding curve in the dark. The apparent dissociation constant calculated from the binding curves at various light intensities is a linear function of the light intensity. Marked differences are observed between the light-induced difference spectra of the fully reduced carboxy-cytochrome c oxidase and the mixed-valence carboxy-cytochrome c oxidase. These differences are enhanced in the presence of ferricyanide as an electron acceptor and are explained by partial oxidation of cytochrome a3 in the mixed-valence enzyme after photodissociation. Upon addition of CO to partially reduced formate cytochrome c oxidase (a2+a3 3+ . HCOOH) the cytochrome a3 2+. CO compound is formed completely with a concomitant oxidation of cytochrome a and the Cu associated with cytochrome a. During photodissociation of the CO compound the formate rebinds to cytochrome a3 and cytochrome a and its associated Cu are simultaneously reduced. These electron transfer processes are fully reversible since in the dark the a3 3+ . HCOOH compound is dissociated slowly with a concomitant formation of the a3 2+ . CO compound and oxidation of cytochrome a. When these experiments are carried out in the presence of cytochrome c, both cytochrome c and cytochrome a are reduced upon illumination of the mixed-valence carboxy-cytochrome c oxidase. In the dark both cytochrome c and cytochrome a are reoxidized when formate dissociates from cytochrome a3 and the a2+ 3 . CO compound is formed back. Thus, in this system we are able to reverse and to modulate the redox state of the different components of the final part of the respiratory chain by light.
在持续光照下，还原型羧基细胞色素c氧化酶的CO结合曲线保持其在黑暗中的结合曲线形状。根据不同光强度下的结合曲线计算出的表观解离常数是光强度的线性函数。在完全还原的羧基细胞色素c氧化酶和混合价羧基细胞色素c氧化酶的光诱导差异光谱之间观察到明显差异。在铁氰化物作为电子受体存在时，这些差异会增强，并且可以用光解离后混合价酶中细胞色素a3的部分氧化来解释。向部分还原的甲酸细胞色素c氧化酶（a2 + a3 3+.. HCOOH）中加入CO后，细胞色素a3 2+.. CO化合物会完全形成，同时细胞色素a和与细胞色素a相关的Cu会发生氧化。在CO化合物的光解离过程中，甲酸会重新结合到细胞色素a3上，细胞色素a及其相关的Cu会同时被还原。这些电子转移过程是完全可逆的，因为在黑暗中，a3 3+.. HCOOH化合物会缓慢解离，同时形成a3 2+.. CO化合物并使细胞色素a氧化。当在细胞色素c存在的情况下进行这些实验时，混合价羧基细胞色素c氧化酶光照后细胞色素c和细胞色素a都会被还原。在黑暗中，当甲酸从细胞色素a3上解离且a2+ 3.. CO化合物重新形成时，细胞色素c和细胞色素a都会被重新氧化。因此，在这个系统中，我们能够通过光来逆转和调节呼吸链最后部分不同组分的氧化还原状态。
