Coelenterazine is a luciferin, a light-emitting biomolecule that serves as a substrate for luciferases or as a constituent of photoproteins, including aequorin. The oxidation of coelenterazine to coelenteramide is accompanied by emission of blue light (emission maximum, 460-470 nm). Luciferase-mediated oxidation of coelenterazine or a derivative is used as an energy donor, typically to a form of green or yellow fluorescent protein, in bioluminescent resonance energy transfer studies. Alternatively, the calcium-mediated release of coelenterazine from aequorin, followed by non-enzymatic oxidation of this compound, results in bioluminescence. As light emission depends on both calcium and cellular redox status, this reaction is used to non-fluorescently detect changes in calcium level and redox status.
