luxCDABE

luxCDABE is a bacterial luciferase operon best known from Vibrio fischeri. It encodes two enzymatic activities that produce bioluminescence: LuxA and LuxB form the luciferase enzyme, a heterodimer that catalyzes light emission, and LuxC, LuxD, and LuxE form a multi-enzyme system that generates the long-chain fatty aldehyde substrate used by luciferase. In many systems, LuxG, a flavin reductase that helps supply reduced flavin mononucleotide (FMNH2), is located nearby or encoded separately. The operon can function autonomously in some hosts, enabling light production without external substrate addition.

Bioluminescence in the luxCDABE system results from the reaction of reduced FMN (FMNH2), molecular oxygen, and a long-chain fatty aldehyde produced by LuxCDE. The overall reaction yields oxidized FMN, a carboxylic acid, water, and light. The aldehyde substrate is synthesized in vivo by the LuxCDE enzymes through an ATP- and CoA-dependent process that converts fatty acyl substrates into the aldehyde that luciferase uses. Oxygen is required for the light-emitting reaction, and the intensity of the glow reflects the expression level of the operon and the metabolic state of the host.

Applications of luxCDABE include its use as a reporter gene in bacteria to monitor promoter activity, gene expression, and cellular viability. Because some configurations provide the substrate in situ, researchers can obtain autonomous luminescence without adding substrate, simplifying real-time in vivo and in vitro assays. Limitations include metabolic burden on the host, energy consumption associated with light production, and variability with growth conditions and oxygen availability. The system remains a foundational tool for real-time bioluminescent reporting in microbiology.

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