Dissimilatory nitrite reductase, a key enzyme in the denitrification pathway, catalyzes the reduction of nitrite to NO. Bioinformatic analysis showed that the genome of a novel nitrite-degrading haloarchaeon Halorussus sp. YCN54 possessed a gene encoding the Cu-containing dissimilatory nitrite reductase (NirK_Hrs). NirK_Hrs was heterologously expressed and purified. Protein sequencing indicated that two isoforms of NirK_Hrs monomer were produced intracellularly. UV–vis spectrum of the purified NirK_Hrs showed that it belonged to the blue NirK group. NirK_Hrs showed optimum activity at 4.5 M NaCl, 55 ℃ and pH 7.0, representing a halophilic, slightly thermophilic and neutral enzyme. It exhibited high stability at 30–50 ℃. NirK_Hrs activity was strongly inhibited by the copper chelating agent due to removal of copper. NirK_Hrs activity was activated by Mn²⁺ and Sr²⁺. It displayed good tolerance to some high polarity organic solvents and nonionic surfactants, such as glycerol, DMSO, DMF and tween-20. Na₂S₂O₄ was an effective electron donor to NirK_Hrs. The K_m and V_max values of purified NirK_Hrs for nitrite were 3.2 mM and 477.2 U/mg, respectively, indicating its high activity. These results indicated that NirK_Hrs may have potential applications for nitrite degradation in high-salt industries, such as salted food and saline wastewater treatment.

中文翻译：

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表征的一种新型的含铜异亚硝酸盐还原酶，从嗜盐古龙Halorussus sp。YCN54。

亚硝酸盐还原酶是反硝化途径中的关键酶，催化亚硝酸盐还原为NO。生物信息学分析表明，一种新型的降解亚硝酸盐的卤代古细菌Halorussus sp。的基因组。YCN54具有编码含Cu的异化亚硝酸盐还原酶（NirK _Hrs）的基因。NirK _Hrs是异源表达和纯化的。蛋白质测序表明，NirK _Hrs单体的两种同工型在细胞内产生。纯化的NirK _Hrs的紫外可见光谱表明，它属于蓝色NirK组。NirK_小时在4.5 M NaCl，55℃和pH 7.0下显示最佳活性，代表一种嗜盐，略嗜热和中性的酶。在30–50℃时显示出高稳定性。由于去除了铜，NirK _Hrs活性被铜螯合剂强烈抑制。NirK _Hrs活性被Mn ²⁺和Sr ²⁺激活。它对某些高极性有机溶剂和非离子表面活性剂（如甘油，DMSO，DMF和tween-20）具有良好的耐受性。Na ₂ S ₂ O ₄是NirK _Hrs的有效电子供体。纯化的NirK _Hrs的K _m和V _max值亚硝酸盐的活度分别为3.2 mM和477.2 U / mg，表明其高活性。这些结果表明，NirK _Hrs可能在高盐行业（如盐渍食品和盐水废水处理）中对亚硝酸盐降解具有潜在的应用。