Stein LY, Arp DJ
Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA.
Appl Environ Microbiol. 1998 Oct;64(10):4098-102. doi: 10.1128/AEM.64.10.4098-4102.1998.
Nitrosomonas europaea, an obligate ammonia-oxidizing bacterium, lost an increasing amount of ammonia oxidation activity upon exposure to increasing concentrations of nitrite, the primary product of ammonia-oxidizing metabolism. The loss of activity was specific to the ammonia monooxygenase (AMO) enzyme, as confirmed by a decreased rate of NH4+-dependent O2 consumption, some loss of active AMO molecules observed by polypeptide labeling with 14C2H2, the protection of activity by substrates of AMO, and the requirement for copper. The loss of AMO activity via nitrite occurred under both aerobic and anaerobic conditions, and more activity was lost under alkaline than under acidic conditions except in the presence of large concentrations (20 mM) of nitrite. These results indicate that nitrite toxicity in N. europaea is mediated by a unique mechanism that is specific for AMO.
欧洲亚硝化单胞菌是一种专性氨氧化细菌，在暴露于不断增加浓度的亚硝酸盐（氨氧化代谢的主要产物）时，其氨氧化活性会不断丧失。活性丧失是氨单加氧酶（AMO）所特有的，这一点通过以下方面得到证实：依赖于NH4+的O2消耗速率降低、用14C2H2进行多肽标记观察到一些活性AMO分子的丧失、AMO底物对活性的保护以及对铜的需求。通过亚硝酸盐导致的AMO活性丧失在有氧和无氧条件下均会发生，并且除了存在高浓度（20 mM）亚硝酸盐的情况外，在碱性条件下比在酸性条件下丧失的活性更多。这些结果表明，欧洲亚硝化单胞菌中亚硝酸盐的毒性是由一种对AMO具有特异性的独特机制介导的。
