Hydroxylamine Complexes of Cytochrome : Influence of Heme Iron Redox State on Kinetic and Spectroscopic Properties.

Hydroxylamine (NHOH or HA) is a redox-active nitrogen oxide that occurs as a toxic intermediate in the oxidation of ammonium by nitrifying and methanotrophic bacteria. Within ammonium containing environments, HA is generated by ammonia monooxygenase (nitrifiers) or methane monooxygenase (methanotrophs). Subsequent oxidation of HA is catalyzed by heme proteins, including cytochromes P460 and multiheme hydroxylamine oxidoreductases, the former contributing to emissions of NO, an ozone-depleting greenhouse gas.