Luciferins (from the Latin lucifer, "light-bringer") are a class of light-emitting heterocyclic compounds found in organisms that cause bioluminescence. Luciferins typically undergo an enzyme-catalysed oxidation and the resulting unstable reaction intermediate emits light upon decaying to its ground state. The term luciferin is also used generically to refer both to the molecules that react with luciferases to emit light and to photoprotein, which emits light without the intervention of an enzyme.
Luciferins are a class of small-molecule substrates that are oxidized in the presence of the enzyme luciferase to produce oxyluciferin and energy in the form of light. It is not known just how many types of luciferins there are, but some of the better-studied compounds are listed below. There are many types of luciferins, yet all share the use of reactive oxygen species to emit light.
Firefly luciferin is the luciferin found in many Lampyridae species. It is the substrate of luciferase (EC 184.108.40.206) responsible for the characteristic yellow light emission from fireflies. The chemistry is unusual, as it was found that ATP is required for light emission.
Bacterial luciferin is a type of luciferin found in bacteria, some of which live within the specialized tissues of some squid and fish. It consists of a long-chain aldehyde and a reduced riboflavin phosphate.
Coelenterazine is found in radiolarians, ctenophores, cnidarians, squid, copepods, chaetognaths, fish, and shrimp. It is the prosthetic group in the protein aequorin responsible for the blue light emission.
Dinoflagellate luciferin is a chlorophyll derivative and is found in dinoflagellates, which are often responsible for the phenomenon of nighttime ocean phosphorescence. A very similar type of luciferin is found in some types of euphausiid shrimp.
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