D-Luciferin is a natural compound isolated from fireflies and is a substrate for the enzyme luciferase. Chemiluminescence at 560 nm is generated when luciferin is oxidized by an ATPdependent process, catalyzed by luciferase. Luciferase is encoded by the luc gene, which is widely used as a reporter gene in a variety of cells. Because of the intrinsic low background of chemiluminescence technique, detection of the luc gene expression can be made at very low level. In addition, luciferin/luciferase has been used to measure 10-15 molar quantity of ATP.
