Firefly luciferase is widely used as a reporter gene for studying gene regulation and function, and for pharmaceutical screening. The enzyme catalyzes ATP-dependent D-luciferin oxidation by oxygen into oxyluciferin with emission of light centered on 560 nm. As with many enzymes, firefly luciferase follows Michaelis-Menten kinetics, and as a result maximum light output is not achieved until the substrates and co-factor are present in large excess. When assayed under these conditions, light emitted from the reaction is directly proportional to the number of luciferase enzyme molecules. The Firefly Luciferase Assay Kit is designed for detection and quantification of firefly luciferase reporter enzyme from cultured cells in a simple, efficient and linear fashion. The kit has reagents sufficient for 1000 assays for plate sizes ranging from 96-well to 24-well.