Mechanisms and applications of bacterial luciferase and its auxiliary enzymes

Bacterial luciferase (LuxAB) catalyzes the conversion of reduced flavin mononucleotide (FMNH⁻), oxygen, and a long-chain aldehyde to oxidized FMN, the corresponding acid and water with concomitant light emission. This bioluminescence reaction requires the reaction of a flavin reductase such as LuxG (in vivo partner of LuxAB) to supply FMNH⁻ for the LuxAB reaction. LuxAB is a well-known self-sufficient luciferase system because both aldehyde and FMNH⁻ substrates can be produced by the associated enzymes encoded by the genes in the lux operon, allowing the system to be auto-luminous. This makes it useful for in vivo applications. Structural and functional studies have long been performed in efforts to gain a better understanding of the LuxAB reaction. Recently, continued exploration of the LuxAB reaction have elucidated the mechanisms of C4a-hydroperoxyflavin formation and identified key catalytic residues such as His44 that facilitates the generation of flavin intermediates important for light generation. Advancements in protein engineering and synthetic biology have improved the bioluminescence properties of LuxAB. Various applications of LuxAB for bioimaging, bioreporters, biosensing in metabolic engineering and real-time monitoring of aldehyde metabolites in biofuel production pathways have been developed during the last decade. Challenging issues such as achieving red-shifted emissions, optimizing the signal intensity and identifying mechanisms related to the generation of light-emitting species remain to be explored. Nevertheless, LuxAB continues to be a promising tool for diverse biotechnological and biomedical applications.