Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Energy-Yielding 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 substances belonging to a special 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 in the form of photons. The emitted light can vary greatly in hue, ranging from blue to red.

A wide variety of organisms are capable of bioluminescence, including Bacteria, Fungi, Protozoa, Mollusks, insects (such as fireflies), Coelenterates, crustaceans, and fish. The luciferins of these organisms vary significantly in Structure and properties. Most of them emit light upon oxidation by interacting 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. During its oxidation in the presence of a long-chain aldehyde (containing at least 8 carbon atoms), the aldehyde is simultaneously oxidized to a carboxylic acid, and the luciferin is oxidized 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 emitted light is characterized by a wavelength of ~490 nm.

Luminous organisms may use bioluminescence for conspecific recognition, luring prey, mating signals, deterring or distracting predators, and illuminating their prey, among other Functions. The Role of bioluminescence in lower organisms, such as bacteria, remains less understood.

It has been suggested that bioluminescence emerged during the evolutionary transition from anaerobic to aerobic Life as a protective mechanism against a potent oxidizing agent—molecular oxygen.