Luciferin

Luciferin refers to a class of light-emitting substrates used by bioluminescent organisms. In living systems, luciferin is oxidized by luciferase enzymes, producing photons; the reaction typically consumes ATP and oxygen and yields an oxidized product plus light.

Firefly luciferin (D-luciferin) and firefly luciferase generate yellow-green light (approximately 530 nm); the reaction yields oxyluciferin, CO2, AMP and PPi, with light emitted. The emission color and efficiency can vary with species, substrate form, and environmental conditions.

Other natural luciferins include coelenterazine used by many marine organisms with their luciferases, emitting blue to green light; and the bacterial luciferin system uses FMNH2 and a long-chain aldehyde with bacterial luciferase, producing blue-green luminescence. Different luciferins pair with specific luciferases, and the emitted light typically ranges from blue to green, depending on the system.

In research and clinical imaging, exogenous luciferins such as D-luciferin are used with luciferase-expressing cells to visualize gene expression, tumor growth, or other biological processes in vivo. Synthetic luciferins have been developed to improve brightness, stability, or to shift emission toward longer wavelengths for better tissue penetration.

Luciferin nomenclature designates the substrate, not the enzyme, and distinct luciferins are matched to their corresponding luciferases. The study of luciferins spans biochemistry, molecular biology, and biomedical imaging, reflecting their broad utility in detecting and monitoring biological activity.