Component of the hydrazine synthase complex that catalyzes the condensation of nitric oxide (NO) with ammonium to form hydrazine (PubMed:21964329). The alpha subunit catalyzes the second half-reaction, i.e. the condensation of hydroxylamine formed in the active site of the gamma subunit with ammonia, yielding hydrazine (PubMed:26479033). Is involved in anaerobic ammonium oxidation (anammox), a biological process in which nitrite is used as the electron acceptor in the conversion of ammonium to dinitrogen gas (N2) and water; this bacterial process has a major role in the Earth's nitrogen cycle and has been estimated to synthesize up to 50% of the dinitrogen gas emitted into our atmosphere from the oceans (PubMed:21964329, PubMed:26479033). 3 Fe(III)-[cytochrome c] + H2O + hydrazine = 3 Fe(II)-[cytochrome c] + 2 H(+) + NH4(+) + nitric oxide Binds two heme c groups per subunit. Nitrogen metabolism. Part of the hydrazine synthase complex that forms an elongated dimer of heterotrimers composed of one alpha, one beta and one gamma subunit. Is among the most highly expressed proteins in the proteome. The alpha subunit consists of three domains: an N-terminal domain which includes a six-bladed beta-propeller, a middle domain binding a pentacoordinated c-type heme and a C-terminal domain which harbors a bis-histidine-coordinated c-type heme.