| Nitrosomonas europaea is a chemolithic, autotrophic bacteria which derives energy by the oxidation of ammonia to nitrite. The ammonia oxidizing enzyme, ammonia monoxygenase (AMO) is a non-specific enzyme which can degrade a wide variety of compounds, including halogenated alkanes, alkenes and aromatics.;Both halogenated alkanes and alkenes were degraded at rates that decreased as the number of halogens on the molecule increased. Since both carbon tetrachloride and tetrachloroethylene were not degraded, a carbon-hydrogen bond may be required for degradation. The cis-alkenes were consistently degraded faster than the trans-alkenes possibly indicating substrate orienting aspects of the active site of AMO. Both 1,1,3-trichloropropene and the mixture of cis- and trans-dibromopropene were irreversible inhibitors of the oxidation of ammonia and hydroxylamine.;Aromatic compounds were oxidized primarily to para-phenolic compounds. The reaction products suggest an enzyme specific binding and oxidation of the substrates so as to favor the 3,4-site on the aryl ring. With mono-deuterated compounds, a deuterium migration was observed during oxidation (NIH shift). Phenolic products that were not derived from an arene oxide intermediate were observed. Cell free extracts, membrane extracts and salt washed membranes, with added cytochrome c-554, oxidized nitrobenzene to nitrophenol. The reaction required hydrazine, hydroxylamine or NADH as a source of electrons and the rates were 10% or less of the whole cell rates.;The commercial nitrification inhibitor, nitrapyrin (2-chloro-6-trichloromethylpyridine) was oxidized at the trichloromethyl group to produce 6-chloropicolinic acid. By use of ;Under nearly anaerobic conditions in the presence of hydrazine, nitrapyrin was reductively dehalogenated. The product of the reaction was identified as 2-chloro-6-dichloromethylpyridine, The specific inhibitors of ammonia oxidation, acetylene and allylthiourea, inhibited the rate of the reaction suggesting that AMO was involved. Aerobic oxidation of 2-chloro-6-dichloromethylpyridine was not observed. It is not known whether the oxidation and reduction reactions have a common intermediate. |
