The Collaborative International Dictionary
Firefly luciferin \Fire"fly` lu*cif"er*in\, n. (Biochem.) a type of luciferin produced by the firefly Photinus pyralis.
Note: Its structure has been elucidated, and chemically it is recognized as
4,5-Dihydro-2-(6-hydroxy-2-benzothiazol-2-yl)-4-thiazolecarboxylic
acid, C11H8N3O2S2. It has found use in a very
sensitive assay for ATP, in which concentrations of ATP
as low as 10^ -11 molar can be detected.
--[MI11]
Wikipedia
Firefly luciferin is the luciferin, or light-emitting compound, found in many firefly ( Lampyridae) species. It is the substrate of luciferase ( EC 1.13.12.7), which is responsible for the characteristic yellow light emission from many firefly species.
As with all other luciferins, oxygen is required to elicit light; however, it has also been found adenosine triphosphate (ATP) and magnesium are required for light emission.