REACTIONS OF NITRIC-OXIDE WITH CYTOCHROME-C OXIDASE
REACTIONS OF NITRIC-OXIDE WITH CYTOCHROME-C OXIDASE
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DOI：
10.1021/bi00564a020
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发表时间：
1980-01-01
期刊：
影响因子：
2.9
通讯作者：
CHAN, SI
中科院分区：
文献类型：
--
作者：
BRUDVIG, GW;STEVENS, TH;CHAN, SI
报道了NO与氧化和还原的[牛肉心脏]细胞色素c氧化酶的反应。利用核磁共振和质谱法测定反应产物；EPR和光谱学被用来确定在这些反应中产生的酶的状态。该酶催化NO的连续氧化和还原。当将NO添加到还原酶、氧化酶或在叠氮化物存在的情况下添加到氧化酶时，观察到不同的循环。通过改变NO的浓度，可以在这3个循环中的每个循环中观察到酶的状态。一氧化氮的反应都涉及一个1电子或2电子氧化还原步骤，并且只能通过细胞色素a3和Cua3的参与来解释。基于这些结果，我们提出了一种酶还原O2的机制，其中细胞色素a3的功能是锚定O2和中间体，同时保持亚铁状态，而Cua3的功能是接受细胞色素a/Cua的电子并将其转移到O2。
The reactions of NO with both oxidized and reduced [beef heart] cytochrome c oxidase are reported. NMR and mass spectroscopy were utilized to determine the products of the reactions; EPR and optical spectroscopy were employed to determine the states of the enzyme produced in each of these reactions. The enzyme catalyzes the consecutive oxidation and reduction of NO. A different cycle was observed when NO was added to the reduced enzyme, to the oxidized enzyme, or to the oxidized enzyme in the presence of azide. It was possible to observe the state of the enzyme at several points in each of these 3 cycles by varying the concentration of NO. The reactions of NO all involved a 1- or 2-electron redox step and could be accounted for by the involvement of only cytochrome a3 and Cua3. On the basis of these results, a mechanism for the reduction of O2 by the enzyme is proposed in which cytochrome a3 functions to anchor O2 and intermediates while remaining in the ferrous state, whereas Cua3 functions to accept electrons from cytochrome a/Cua and transfer them to O2.