Purification and characterization of a low-temperature ammonia monooxygenase from heterotrophic nitrifier Acinetobacter sp. Y16

Abstract

Low-temperature ammonia monooxygenase (AMO) was purified from a heterotrophic nitrifier Acinetobacter sp. Y16 by anion-exchange and gel-filtration chromatography. The purified enzyme was a membrane-bound monomer with a molecular mass of approximately 31 kDa. It could catalyze the oxidation of ammonium without stabilizing agents in vitro at low temperature. Addition of CuCl₂ could stimulate AMO activity in vitro. The enzyme was stable in the temperature range of 4–15°C with less than 9% change in its activity. The optimal activity temperature was 15°C. Above 20°C, the enzyme completely lost its activity. The enzyme activity was stable when stored at 4°C for five days, at 10°C for two days, and at 15°C for one day. This study purified a highly pure AMO from a heterotrophic nitrifier Acinetobacter sp. for the first time.

Keywords:

• Purification
• Ammonia monooxygenase
• Heterotrophic nitrifier
• Acinetobacter sp. Y16

Acknowledgements

This study is supported by the grants from the National Natural Science Foundation of China (51078106), Project of Outstanding Academic Youth of Heilongjiang Province (1251G049), Heilongjiang Provincial Science Foundation for Distinguished Youth Scholar (JC200708), and Heilongjiang Provincial Finance Foundation for Basic Sciences (CZ12BZSM06).