Evidence that ferredoxin interfaces with an internal redox shuttle in Acetyl-CoA synthase during reductive activation and catalysis.
Evidence that ferredoxin interfaces with an internal redox shuttle in Acetyl-CoA synthase during reductive activation and catalysis.
复制标题
DOI：
10.1021/bi101511r
复制
发表时间：
2011-01-18
期刊：
影响因子：
2.9
通讯作者：
Ragsdale SW
中科院分区：
文献类型：
--
作者：
Bender G;Ragsdale SW
乙酰辅酶A合酶（ACS）是Moorella thermoacetica的双功能CO脱氢酶/乙酰辅酶A合酶（CODH/ACS）复合物的一个亚基，需要还原活化以催化乙酰辅酶A合成和相关的部分反应，包括CO/[1- 14 C]-乙酰辅酶A交换反应。我们表明，M。热乙酸铁氧还蛋白（II）（Fd-II）是ACS的氧化还原激活剂，它具有两个[4Fe-4S]簇，是CODH的电子受体。活化水平取决于ACS和Fd-II的氧化态，这强烈表明Fd-II充当还原剂。通过使用受控电位酶学，在CO/乙酰辅酶A交换反应中催化性单电子氧化还原活性物质的中点还原电位为−511 mV，这与先前在涉及ACS的其他反应中测量的中点还原电位相似。ACS与Fd-II和CO的孵育导致NiFeC物种的形成，这也支持Fd-II作为ACS的还原剂的作用。除了作为还原剂，Fd-II可以接受来自乙酰化ACS的电子，如通过还原Fd-II的EPR谱的强度增加所观察到的，这表明在ACS的乙酰基-Ni（II）形式中的“电子穿梭”内存在储存的电子。这种“穿梭”被提议在活化期间和ACS催化循环的不同步骤中充当氧化还原介体。
Acetyl-CoA synthase (ACS), a subunit of the bifunctional CO dehydrogenase/acetyl-CoA synthase (CODH/ACS) complex of Moorella thermoacetica requires reductive activation in order to catalyze acetyl-CoA synthesis and related partial reactions, including the CO/[1-14C]-acetyl-CoA exchange reaction. We show that the M. thermoacetica ferredoxin(II) (Fd-II), which harbors two [4Fe-4S] clusters and is an electron acceptor for CODH, serves as a redox activator of ACS. The level of activation depends on the oxidation states of both ACS and Fd-II, which strongly suggests that Fd-II acts as a reducing agent. By the use of controlled potential enzymology, the midpoint reduction potential for the catalytic one-electron redox-active species in the CO/acetyl-CoA exchange reaction is −511 mV, which is similar to the midpoint reduction potential that was earlier measured for other reactions involving ACS. Incubation of ACS with Fd-II and CO leads to the formation of the NiFeC species, which also supports the role of Fd-II as a reductant for ACS. In addition to being a reductant, Fd-II can accept electrons from acetylated ACS, as observed by the increased intensity of the EPR spectrum of reduced Fd-II, indicating that there is a stored electron within an “electron shuttle” in the acetyl-Ni(II) form of ACS. This “shuttle” is proposed to serve as a redox mediator during activation and at different steps of the ACS catalytic cycle.
登录
查看更多内容
影响因子：
15
作者：
Barondeau, DP;Lindahl, PA
通讯作者：
Lindahl, PA
影响因子：
15
作者：
George, SJ;Seravalli, J;Ragsdale, SW
通讯作者：
Ragsdale, SW
影响因子：
2.9
作者：
Dorweiler, JS;Finke, RG;Matthews, RG
通讯作者：
Matthews, RG
影响因子：
3.2
作者：
LUNDIE, LL;DRAKE, HL
通讯作者：
DRAKE, HL
影响因子：
4.8
作者：
Gao-Sheridan, HS;Pershad, HR;Burgess, BK
通讯作者：
Burgess, BK