The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics.
The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics.
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DOI：
10.1128/ecosalplus.3.2.2
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发表时间：
2008-03
期刊：
影响因子：
--
通讯作者：
G. Unden;Pia Dünnwald
中科院分区：
文献类型：
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作者：
G. Unden;Pia Dünnwald
大肠杆菌含有一个多功能的呼吸链，它氧化10种不同的电子供体底物，并将电子转移到末端还原酶或氧化物酶，从而还原6种不同的电子受体。沙门氏菌甚至可以使用另外两个电子受体。某些底物的同工酶的存在进一步增加了这种变异。不同的电子供体和受体的氧化可以通过结合不同的电子供体和受体来建立，这些电子供体和受体通过呼吸醌连接在一起。这些酶在结构、膜拓扑结构和能量守恒模式方面有很大的不同。大多数能量守恒的脱氢酶(如FdnGHI、HyaABC和HybCOAB)和末端还原酶(CydAB、NarGHi等)通过氧化还原环机制形成质子势(Δp)。只有两种酶(NuoA-N和CyoABCD)通过质子泵将氧化还原能量偶联到质子转运。大量脱氢酶(如NDH、SdhABCD和GlpD)和末端还原酶(如FrdABCD和DmsABC)不能在质子势中保存氧化还原能量。对于大多数呼吸酶来说，质子势能的产生机制是通过结构和生化研究得知的，或者可以根据序列信息进行预测。大多数呼吸链质子转运的H+/2E−比值在2~6H+/2E−之间。描述了各个氧化还原反应和呼吸链的能量学。与有关酶功能的知识形成对比的是呼吸作用的生理方面，如电子传递的组织和协调以及替代呼吸酶的使用，这些方面还没有得到很好的描述。
Escherichia coli contains a versatile respiratory chain which oxidizes ten different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use even two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. Various respiratory pathways can be established by combining the oxidation of different electron donors and acceptors which are linked by respiratory quinones. The enzymes vary largely with respect to architecture, membrane topology, and mode of energy conservation. Most of the energy-conserving dehydrogenases (e.g., FdnGHI, HyaABC, and HybCOAB) and of the terminal reductases (CydAB, NarGHI, and others) form a proton potential (Δp) by a redox loop mechanism. Only two enzymes (NuoA-N and CyoABCD) couple the redox energy to proton translocation by proton pumping. A large number of dehydrogenases (e.g., Ndh, SdhABCD, and GlpD) and of terminal reductases (e.g., FrdABCD and DmsABC) do not conserve the redox energy in a proton potential. For most of the respiratory enzymes, the mechanism of proton potential generation is known from structural and biochemical studies or can be predicted from sequence information. The H+/2e− ratios of proton translocation for most respiratory chains are in the range from 2 to 6 H+/2e−. The energetics of the individual redox reactions and of the respiratory chains is described. In contrast to the knowledge on enzyme function are physiological aspects of respiration such as organization and coordination of the electron transport and the use of alternative respiratory enzymes, not well characterized.