Catalyzes the reduction of N-oxygenated molecules, acting as a counterpart of cytochrome P450 and flavin-containing monooxygenases in metabolic cycles. As a component of prodrug-converting system, reduces a multitude of N-hydroxylated prodrugs particularly amidoximes, leading to increased drug bioavailability. May be involved in mitochondrial N(omega)-hydroxy-L-arginine (NOHA) reduction, regulating endogenous nitric oxide levels and biosynthesis. Postulated to cleave the N-OH bond of N-hydroxylated substrates in concert with electron transfer from NADH to cytochrome b5 reductase then to cytochrome b5, the ultimate electron donor that primes the active site for substrate reduction. 2 Fe(II)-[cytochrome b5] + 2 H(+) + N(omega)-hydroxy-L-arginine = 2 Fe(III)-[cytochrome b5] + H2O + L-arginine Binds 1 Mo-molybdopterin (Mo-MPT) cofactor per subunit. Component of a complex composed of cytochrome b5, NADH-cytochrome b5 reductase and MTARC1. Mitochondrial import is mediated by AA 1-40 and requires ATP. Comprises two structural domains, the molybdenum cofactor/Moco sulfurase C-terminal (MOSC) domain and the MOSC N-terminal region, forming a cleft that accommodates Moco. The MOSC domain, which contains a large seven-stranded mostly antiparallel beta-barrel, engages multiple interactions with Moco both pterin ring and phosphate group, allowing for a tight coordination of Moco within the core of the enzyme. Truncated N-terminus.