School of Computing Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, U.K.
Microbiologyopen. 2013 Oct;2(5):756-65. doi: 10.1002/mbo3.111. Epub 2013 Jul 30.
When denitrifying bacteria such as Paracoccus denitrificans respire anaerobically they convert nitrate to dinitrogen gas via a pathway which includes the potent greenhouse gas, nitrous oxide (N2 O). The copper-dependent enzyme Nitrous Oxide reductase (Nos) catalyzes the reduction of N2 O to dinitrogen. In low-copper conditions, recent experiments in chemostats have demonstrated that Nos efficiency decreases resulting in significant N2 O emissions. For the first time, a chemostat-based mathematical model is developed that describes the anaerobic denitrification pathway based on Michaelis-Menten kinetics and published kinetic parameters. The model predicts steady-state enzyme levels from experimental data. For low copper concentrations, the predicted Nos level is significantly reduced, whereas the levels for the non copper-dependent reductases in the pathway remain relatively unaffected. The model provides time courses for the pathway metabolites that accurately reflect previously published experimental data. In the absence of experimental data purely predictive analyses can also be readily performed by calculating the relative Nos level directly from the copper concentration. Here, the model quantitatively estimates the increasing level of emitted N2 O as the copper level decreases.
当反硝化细菌（如脱氮副球菌）进行无氧呼吸时，它们会通过一条途径将硝酸盐转化为氮气，其中包括一种强温室气体——一氧化二氮（N2O）。铜依赖性酶一氧化二氮还原酶（Nos）催化 N2O 还原为氮气。在低铜条件下，最近在恒化器中的实验表明，Nos 的效率降低，导致大量 N2O 排放。本文首次开发了一种基于米氏动力学和已发表动力学参数的基于恒化器的数学模型，该模型描述了基于无氧反硝化途径。该模型从实验数据预测稳态酶水平。对于低铜浓度，预测的 Nos 水平显著降低，而途径中不依赖铜的还原酶水平相对不受影响。该模型提供了途径代谢物的时间过程，这些时间过程准确反映了先前发表的实验数据。在没有实验数据的情况下，通过直接从铜浓度计算相对 Nos 水平，也可以轻松进行纯预测分析。在这里，该模型定量估计了随着铜浓度降低，排放的 N2O 水平的增加。
