In enzymology, a hyponitrite reductase is an enzyme that catalyzes the oxidation of hydroxylamine by the nicotinamide adenine dinucleotide cation (NAD+) into hyponitrous acid HON=NOH: 2 + 2 NAD+ HON=NOH + 2 NADH + 2 H+ This systematic name of this enzyme class hydroxylamine:NAD+ oxidoreductase. It is also called NADH2:hyponitrite oxidoreductase. This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with NAD+ or NADP+ as acceptor. It employs one cofactor, metal. References EC 1.7.1 NADH-dependent enzymes Metal enzymes Enzymes of unknown structure