Schmidt Ingo, Bock Eberhard, Jetten Mike S M
Department of Microbiology, University of Nijmegen, Toernooidveld 1, 6525 ED Nijmegen, The Netherlands1.
Institute for General Botany, Department of Microbiology, University of Hamburg, Ohnhorststraße 18, 22609 Hamburg, Germany2.
Microbiology (Reading). 2001 Aug;147(Pt 8):2247-2253. doi: 10.1099/00221287-147-8-2247.
The effect of acetylene ((14)C(2)H(2)) on aerobic and anaerobic ammonia oxidation by Nitrosomonas eutropha was investigated. Ammonia monooxygenase (AMO) was inhibited and a 27 kDa polypeptide (AmoA) was labelled during aerobic ammonia oxidation. In contrast, anaerobic, NO(2)-dependent ammonia oxidation (NO(2)/N(2)O(4) as oxidant) was not affected by acetylene. Further studies gave evidence that the inhibition as well as the labelling reaction were O(2)-dependent. Cells pretreated with acetylene under oxic conditions were unable to oxidize ammonia with O(2) as oxidant. After these cell suspensions were supplemented with gaseous NO(2), ammonia oxidation activity of about 140 micromol NH(4)(+) (g protein)(-1) h(-1) was detectable under both oxic and anoxic conditions. A significantly reduced acetylene inhibition of the ammonia oxidation activity was observed for cells incubated in the presence of NO. This suggests that NO and acetylene compete for the same binding site on AMO. On the basis of these results a new hypothetical model of ammonia oxidation by N. eutropha was developed.
研究了乙炔（(14)C₂H₂）对嗜养亚硝化单胞菌好氧和厌氧氨氧化的影响。在好氧氨氧化过程中，氨单加氧酶（AMO）受到抑制，且一个27 kDa的多肽（AmoA）被标记。相反，厌氧的、依赖NO₂的氨氧化（以NO₂/N₂O₄作为氧化剂）不受乙炔影响。进一步研究表明，抑制作用以及标记反应都依赖于O₂。在有氧条件下用乙炔预处理的细胞无法以O₂作为氧化剂氧化氨。在这些细胞悬液补充气态NO₂后，在有氧和无氧条件下均可检测到约140 μmol NH₄⁺（g蛋白）⁻¹ h⁻¹的氨氧化活性。在NO存在下培养的细胞中，观察到氨氧化活性的乙炔抑制作用显著降低。这表明NO和乙炔竞争AMO上的相同结合位点。基于这些结果，建立了嗜养亚硝化单胞菌氨氧化的新假设模型。
