Firefly luciferin is the luciferin found in many Lampyridae species. It is the substrate of beetle luciferases (EC 1.13.12.7) responsible for the characteristic yellow light emission from fireflies, though can cross-react to produce light with related enzymes from non-luminous species. The chemistry is unusual, as adenosine triphosphate (ATP) is required for light emission, in addition to molecular oxygen.