Another enzyme that uses FMN as a cofactor is flavin reductase P. NAD(P)H: flavin oxidoreductases (flavin reductases) catalyze the reduction of flavin by using NAD(P)H. They are involved in the role of bacterial bioluminescence. They have been detected in luminous bacteria where they are believed to provide FMNH2 (reduced FMN) to luciferase in vivo where it acts as a substrate for the luminescence reaction.