Koutný M
Department of Environmental Technology, Faculty of Technology Zlín, Brno University of Technology, 762 72 Zlín, Czechia.
Folia Microbiol (Praha). 2000;45(3):197-203. doi: 10.1007/BF02908943.
The review briefly summarizes current knowledge of the bacterial nitric-oxide reductase (NOR). This membrane enzyme consists of two subunits, the smaller one contains haem C and the larger one two haems B and nonhaem iron. The protein sequence and structure of metal centres demonstrate the relationship of NOR to the family of terminal oxidases. The binuclear Fe-Fe reaction centre, consisting of antiferromagnetically coupled haem B and nonhaem iron, is analogous to Fe-Cu centre of terminal oxidases. The data on the structure and function of NOR and terminal oxidases suggest that all these enzymes are closely evolutionally related. The catalytic properties are determined most of all by the relatively high toxicity of nitric oxide as a substrate and the resulting strong need to maintain its concentration at nanomolar levels. A kinetic model of the action of the enzyme comprises substrate inhibition. NOR does not conserve the free energy of nitric oxide reduction because it does not work as a proton pump and, moreover, the protons coming into the reaction are taken from periplasm, i.e. they do not cross the membrane.
本综述简要总结了目前关于细菌一氧化氮还原酶（NOR）的知识。这种膜酶由两个亚基组成，较小的亚基含有血红素C，较大的亚基含有两个血红素B和非血红素铁。金属中心的蛋白质序列和结构表明了NOR与末端氧化酶家族的关系。由反铁磁耦合的血红素B和非血红素铁组成的双核Fe-Fe反应中心类似于末端氧化酶的Fe-Cu中心。关于NOR和末端氧化酶的结构与功能的数据表明，所有这些酶在进化上密切相关。催化特性主要由一氧化氮作为底物的相对高毒性以及由此产生的将其浓度维持在纳摩尔水平的强烈需求所决定。该酶作用的动力学模型包括底物抑制。NOR不保存一氧化氮还原的自由能，因为它不作为质子泵起作用，而且进入反应的质子来自周质，即它们不穿过膜。
