Bacterial luciferase requires one reduced flavin for light emission.

Recent reports revive a hypothesis that the bacterial bioluminescence reaction involves two reduced flavin mononucleotide molecules per enzyme turnover. A two-flavin mechanism requires that the two flavins bind simultaneously or sequentially to the same or different sites on luciferase during a catalytic cycle. Measurements using equilibrium techniques show that the luciferase dimer has only a single reduced flavin binding site. Quantum yield results demonstrate that bioluminescence requires only one reduced flavin per luciferase, ruling out mechanisms involving either two reduced flavins or one reduced flavin plus one oxidized flavin per catalytic cycle.