Irisa Tatsuya, Hira Daisuke, Furukawa Kenji, Fujii Takao
Department of Applied Life Science, Sojo University, 4-22-1 Ikeda, Nishiku, Kumamoto 860-0082, Japan.
Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuoku, Kumamoto 860-8555, Japan.
J Biosci Bioeng. 2014 Dec;118(6):616-21. doi: 10.1016/j.jbiosc.2014.05.018. Epub 2014 Jul 1.
The hydroxylamine oxidoreductase (HAO) from the anammox bacterium, Candidatus Kuenenia stuttgartiensis has been reported to catalyze the oxidation of hydroxylamine (NH2OH) to nitric oxide (NO) by using bovine cytochrome c as an oxidant. In contrast, we investigated whether the HAO from anammox bacterium strain KSU-1 could catalyze the reduction of NO with reduced benzyl viologen (BVred) and the NO-releasing reagent, NOC 7. The reduction proceeded, resulting in the formation of NH2OH as a product. The oxidation rate of BVred was proportional to the concentration of BVred itself for a short period in each experiment, a situation that was termed quasi-steady state. The analyses of the states at various concentrations of HAO allowed us to determine the rate constant for the catalytic reaction, (2.85 ± 0.19) × 10(5) M(-1) s(-1), governing NO reduction by BVred and HAO, which was comparable to that reported for the HAO from the ammonium oxidizer, Nitrosomonas with reduced methyl viologen. These results suggest that the anammox HAO functions to adjust anammox by inter-conversion of NO and NH2OH depending on the redox potential of the physiological electron transfer protein in anammox bacteria.
据报道，厌氧氨氧化细菌“斯图加特库氏菌（Candidatus Kuenenia stuttgartiensis）”中的羟胺氧化还原酶（HAO）可利用牛细胞色素c作为氧化剂，将羟胺（NH2OH）氧化为一氧化氮（NO）。相比之下，我们研究了厌氧氨氧化细菌菌株KSU-1中的HAO是否能够催化用还原型苄基紫精（BVred）和NO释放试剂NOC 7还原NO。还原反应进行，生成了产物NH2OH。在每个实验中，短时间内BVred的氧化速率与BVred自身的浓度成正比，这种情况被称为准稳态。对不同浓度HAO状态的分析使我们能够确定催化反应的速率常数，即（2.85±0.19）×10⁵ M⁻¹ s⁻¹，它控制着BVred和HAO对NO的还原，这与报道的来自铵氧化菌“亚硝化单胞菌（Nitrosomonas）”的HAO用还原型甲基紫精还原NO的速率常数相当。这些结果表明，厌氧氨氧化HAO的功能是根据厌氧氨氧化细菌中生理电子传递蛋白的氧化还原电位，通过NO和NH2OH的相互转化来调节厌氧氨氧化过程。
