Part of the ammonia monooxygenase complex, which catalyzes the oxidation of ammonia to hydroxylamine, the first reaction in the process of ammonia oxidation to nitrite. Binds 1 heme c group covalently per subunit. The soluble ammonia monooxygenase is a nonamer composed of three alpha subunits (AmoA), three beta subunits (AmoB) and three gamma subunits (Cytochrome c1 PetC). Ammonia monooxygenase is active and distributed approximately equally in both subcellular fractions. Belongs to the cytochrome c family. Substoichiometric amounts of non-heme iron (about 1 iron atom per ammonia monooxygenase complex) have been found, however it does not seem to function as a cofactor.