JBIC Journal of Biological Inorganic Chemistry ( IF 2.7 ) Pub Date : 2020-08-26 , DOI: 10.1007/s00775-020-01812-0 Cíntia Carreira 1, 2 , Rute F Nunes 1 , Olga Mestre 1 , Isabel Moura 2 , Sofia R Pauleta 1
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Abstract
Increasing atmospheric concentration of N2O has been a concern, as it is a potent greenhouse gas and promotes ozone layer destruction. In the N-cycle, release of N2O is boosted upon a drop of pH in the environment. Here, Marinobacter hydrocarbonoclasticus was grown in batch mode in the presence of nitrate, to study the effect of pH in the denitrification pathway by gene expression profiling, quantification of nitrate and nitrite, and evaluating the ability of whole cells to reduce NO and N2O. At pH 6.5, accumulation of nitrite in the medium occurs and the cells were unable to reduce N2O. In addition, the biochemical properties of N2O reductase isolated from cells grown at pH 6.5, 7.5 and 8.5 were compared for the first time. The amount of this enzyme at acidic pH was lower than that at pH 7.5 and 8.5, pinpointing to a post-transcriptional regulation, though pH did not affect gene expression of N2O reductase accessory genes. N2O reductase isolated from cells grown at pH 6.5 has its catalytic center mainly as CuZ(4Cu1S), while that from cells grown at pH 7.5 or 8.5 has it as CuZ(4Cu2S). This study evidences that an in vivo secondary level of regulation is required to maintain N2O reductase in an active state.
Graphic abstract
中文翻译：
pH值对马氏杆菌碳氢破质反硝化途径和一氧化二氮还原酶的影响。
摘要
大气中N 2 O浓度的增加一直是个问题，因为它是一种有力的温室气体，会破坏臭氧层。在N循环中，环境pH下降会促进N 2 O的释放。在这里，碳氢螯合菌Marinobacterhydrocarbonoclasticus在硝酸盐存在下分批生长，以通过基因表达谱分析，硝酸盐和亚硝酸盐定量以及评估全细胞还原NO和N 2 O的能力来研究pH对反硝化途径的影响。。在pH 6.5时，发生在培养基中的亚硝酸盐的累积和细胞不能减少氮素2 O.此外，N的生物化学性质2首次比较了从在pH 6.5、7.5和8.5下生长的细胞分离的O还原酶。尽管pH值不会影响N 2 O还原酶辅助基因的基因表达，但在酸性pH值时该酶的量低于在pH 7.5和8.5时的量，这是转录后调控的精确定位。从pH 6.5生长的细胞中分离出的N 2 O还原酶的催化中心主要为CuZ（4Cu1S），而从pH 7.5或8.5生长的细胞中分离出的N 2 O催化中心为CuZ（4Cu2S）。这项研究证明，需要体内二级调控才能将N 2 O还原酶维持在活跃状态。
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