Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase
Nitric oxide is an obligate bacterial nitrification intermediate produced by hydroxylamine oxidoreductase
复制标题
DOI：
10.1073/pnas.1704504114
复制
发表时间：
2017-08-01
影响因子：
11.1
通讯作者：
Lancaster, Kyle M.
中科院分区：
文献类型：
--
作者：
Caranto, Jonathan D.;Lancaster, Kyle M.
氨(NH3)-氧化细菌(AOB)释放大量的一氧化氮(NO)和一氧化二氮(N2O)，这两种物质都会对大规模农业产生有害的环境副作用。目前公认的AOB代谢模型包括氨氧化为亚硝酸盐(NO2-)，通过单一的预留中间体羟胺(NH2OH)。在这个模型中，多血红素酶羟胺氧化还原酶(HAO)催化NH_2OH四电子氧化为NO2-。我们提供了HAO在厌氧和好氧条件下仅以三个电子将NH_2OH氧化为NO的证据。在HAO活性测定中观察到的NO2-是在好氧条件下由O-2氧化NO的非酶产物。我们目前的研究表明，AOB的好氧NH3氧化通过两个专有中间体NH_2OH和NO发生，需要第三步酶促反应的介体。
Ammonia (NH3)-oxidizing bacteria (AOB) emit substantial amounts of nitric oxide (NO) and nitrous oxide (N2O), both of which contribute to the harmful environmental side effects of large-scale agriculture. The currently accepted model for AOB metabolism involves NH3 oxidation to nitrite (NO2-) via a single obligate intermediate, hydroxylamine (NH2OH). Within this model, the multi-heme enzyme hydroxylamine oxidoreductase (HAO) catalyzes the four-electron oxidation of NH2OH to NO2-. We provide evidence that HAO oxidizes NH2OH by only three electrons to NO under both anaerobic and aerobic conditions. NO2- observed in HAO activity assays is a nonenzymatic product resulting from the oxidation of NO by O-2 under aerobic conditions. Our present study implies that aerobic NH3 oxidation by AOB occurs via two obligate intermediates, NH2OH and NO, necessitating a mediator of the third enzymatic step.