Cytochrome components which participate in the oxidation of nitrite in Nitrobacter winogradskyi have been highly purified and their properties studied in detail. Cytochrome a1c1 is an iron-sulphur molybdoenzyme which has haems a and c and acts as a nitrite-cytochrome c oxidoreductase. Cytochrome c-550 is homologous to eukaryotic cytochrome c and acts as the electron mediator between cytochrome a1c1 and aa3-type cytochrome c oxidase. The oxidase is composed of two kinds of subunits, has two molecules of haem a and two atoms of copper in the molecule, and oxidizes actively eukaryotic ferrocytochrome c as well as its own ferrocytochrome c-550. Further, a flavoenzyme has been obtained which has transhydrogenase activity and catalyses reduction of NADP+ with benzylviologen radical. This enzyme may be responsible for production of NADPH in N. winogradskyi. The electron transfer against redox potential from NO2- to cytochrome c could be pushed through prompt removal by cytochrome aa3 of H+ formed by the dehydrogenation of NO2- + H2O. As cytochrome c in anaerobically kept cell-free extracts is rapidly reduced on addition of NO2-, a membrane potential does not seem necessary for the reduction of cytochrome c by cytochrome a1c1 with NO2- in vivo.

中文翻译：

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硝酸亚硝酸盐氧化系统。

高度纯化了参与硝化硝化细菌中亚硝酸盐氧化的细胞色素成分，并对其特性进行了详细研究。细胞色素a1c1是一种铁硫钼酶，具有血红素a和c，并充当亚硝酸盐-细胞色素c氧化还原酶。细胞色素c-550与真核细胞色素c同源，并充当细胞色素a1c1和aa3型细胞色素c氧化酶之间的电子介体。氧化酶由两种亚基组成，分子中有两个血红素a分子和两个铜原子，并能主动氧化真核细胞色素c和其自身的色素c-550。此外，已经获得了具有转氢酶活性并催化用苄基紫罗兰自由基还原NADP +的黄素酶。该酶可能负责N中NADPH的产生。温诺格拉茨基。通过NO2- + H2O脱氢形成的H +的细胞色素aa3迅速去除，可以推动从NO2-到氧化还原电位的电子转移到细胞色素c。由于厌氧保存的无细胞提取物中的细胞色素c在添加NO 2后迅速减少，因此在体内用NO 2减少细胞色素a1c1减少细胞色素c似乎不需要膜电位。