Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Energy-storing processes
Capture of light energy by biomolecules
Bioluminescence

Bioluminescence refers to the ability of living organisms to emit visible light. This phenomenon is based on the enzymatic aerobic oxidation of compounds belonging to a distinct family known as luciferins. The Enzymes that catalyze this process are called luciferases. The energy released during The oxidation of luciferins is converted into electronic excitation energy of molecules capable of emitting it as photons. The emitted light can span a wide range of colors, from blue to red.

Numerous organisms are capable of bioluminescence, including Bacteria, Fungi, Protozoa, Mollusks, insects (such as fireflies), Coelenterates, crustaceans, and fish, among others. The luciferins of these species vary significantly in Structure and properties. Most of them emit light upon oxidation through interaction with O₂. However, certain luciferins—such as the photoprotein found in jellyfish—are activated by Calcium Ions.

In luminous bacteria, FMNH₂ acts as the luciferin. Its oxidation in the presence of a long-chain aldehyde (containing at least 8 carbon atoms) results in the simultaneous oxidation of the aldehyde to a carboxylic acid and the luciferin to FMN:

Class="center">FMNH₂ + O₂ + R—CHO + luciferase →

→ FMN + H₂O + R—COOH + photon

This reaction presumably proceeds via a flavin mononucleotide peroxide intermediate, and the resulting luminescence is characterized by a wavelength of ~490 nm.

Luminous organisms utilize bioluminescence for various purposes, such as conspecific recognition, prey attraction, mating signals, predator deterrence and distraction, and illuminating prey. The function of bioluminescence in lower organisms, such as bacteria, remains less understood.

One prevailing hypothesis suggests that bioluminescence emerged during the evolutionary transition from anaerobic to aerobic Life as a protective mechanism against a potent oxidant: molecular oxygen.