Involved in bioluminescence. It is a good supplier of reduced flavin mononucleotide (FMNH2) to the bioluminescence reaction. Major FMN reductase. It is capable of using both NADH and NADPH as electron donors. As electron acceptor, FMN is the most effective, FAD is considerably effective, and riboflavin is the least effective. Homodimer. Belongs to the nitroreductase family.