好氧氨氧化过程中的关键酶及N_(2)O排放研究进展

Key enzymes and N_(2)O emission in aerobic ammonia oxidation process

氧化亚氮(nitrous oxide,N_(2)O)排放量的持续增加对全球生态平衡造成了严重的威胁。微生物N_(2)O排放占主要来源。其中,好氧氨氧化过程是氨在有氧的条件下氧化为亚硝酸盐,其直接或间接地影响着全球产生N_(2)O与释放量。氨氧化古菌(ammonia-oxidizing archaea,AOA)、氨氧化细菌(ammonia-oxidizing bacteria,AOB)、全程氨氧化菌(complete ammonia oxidization,Comammox)和异养氨氧化菌(heterotrophic ammonium oxidizing bacteria,HAOB)是氨氧化过程中主要的参与者,明确这四类微生物N_(2)O产生的机制对缓解全球N_(2)O排放是必要的。本文综述了AOA、AOB、Comammox和HAOB在好氧氨氧化过程中驱动的N_(2)O产生途径,并结合酶学分析了一些关键酶在N_(2)O产生途径中的作用。本文旨在为调控生物N_(2)O排放提供理论基础。

The increasing emission of nitrous oxide(N_(2)O)poses a serious threat to global ecological balance,to which microbes contribute a lot.Aerobic ammonia oxidation is the oxidation of ammonia to nitrite under aerobic conditions,which directly or indirectly affects the global production and release of N_(2)O.Ammonia-oxidizing archaea(AOA),ammonia-oxidizing bacteria(AOB),complete ammonia oxidizers(Comammox),and heterotrophic ammonia-oxidizing bacteria(HAOB)are major contributors to ammonia oxidation.It is important for the mitigation of N_(2)O emission to clarify how N_(2)O is produced by the four types of microorganisms.This paper reviewed the N_(2)O production pathways in AOA,AOB,Comammox and HAOB driven by the aerobic ammonia oxidation process.The roles of some key enzymes in the N_(2)O production pathways were elucidated through enzymatic analysis.Ammonia monooxygenase(AMO)is the first key enzyme in the autotrophic aerobic ammonia oxidation process,and the direct product of hydroxylamine oxidation is NO instead of NO_(2)^(–),which is then converted to NO_(2)^(–)by an unknown enzyme.The aerobic ammonia oxidation process and related enzymes of HAOB are not completely clear,and the issue of N_(2)O emission needs to be further studied.This paper aims to lay a theoretical basis for regulating biological N_(2)O emission.