The emission of light by biological species (bioluminescence) is a fascinating process found in diverse organisms such as bacteria, fungi, insects, fish and nematodes. In all cases the bioluminescent process is based on a chemiluminescent reaction in which the chemical energy is transformed into light energy. Although the underlying chemistry is as diverse as the range and distribution of light-emitting biological species, all bioluminescent processes require a luciferase, i.e. an enzyme catalyzing the chemiluminescent reaction, and a luciferin, which can be considered a coenzyme for the reaction. During the reaction the luciferin is generated in an excited state and serves as the emitter of light energy. In our study, we are interested in the bioluminescence of marine photobacteria. In these bacteria, luciferase is composed of an alpha/beta-heterodimeric protein, which binds reduced flavinmononucleotide (FMN). The reduced FMN reacts with molecular dioxygen to a reactive hydroperoxide intermediate with subsequent oxidation of a long-chain fatty aldehyde (e.g. tetradecanal) to the corresponding fatty acid. During this oxidation process, an excited flavin intermediate is generated which emits light centered at 490 nm. Some marine photobacteria possess an additional gene, luxF, encoding a protein similar to the beta-subunit of luciferase. This protein binds a myristylated flavin derivative where the C-3 atom of myristic acid is covalently attached to the 6-position of the flavin ring system. It was postulated that this flavin adduct is generated in the luciferase catalyzed bioluminescent reaction. Furthermore, it was speculated that luxF sequesters the myristylated flavin adduct in order to prevent inhibition of the luciferase. However, both hypotheses have not been tested on a biochemical or physiological level. Hence, we will identify the biochemical process yielding the flavin adduct and analyze the relationship to the bioluminescent reaction. Our approach will contribute to a more comprehensive understanding of the luciferase reaction and expand our knowledge to the functional role of luxF in bioluminescent marine photobacteria.