The protein encoded by this gene is an enzyme found in the outer mitochondrial membrane that reduces N-hydroxylated substrates. The encoded protein uses molybdenum as a cofactor and cytochrome b5 type B and NADH cytochrome b5 reductase as accessory proteins. One type of substrate used is N-hydroxylated nucleotide base analogues, which can be toxic to a cell. Other substrates include N(omega)-hydroxy-L-arginine (NOHA) and amidoxime prodrugs, which are activated by the encoded enzyme. Multiple transcript variants encoding the different isoforms have been found for this gene. [provided by RefSeq, Sep 2016].