Manfred Kurfürst

Biochemistry and Physiology of Bioluminescent Bacteria

Publisher Summary This chapter describes the biochemistry and physiology of bioluminescent bacteria. The function of bioluminescent bacteria is to emit light in biological systems. The chapter explains the variety of habitats in which these bacteria are found, the light-emitting system may play an important role in their ecology or physiology. The luciferase in bacteria, unlike that of any other luminous group (except, perhaps, the fungi), is related to the respiratory pathway, functioning as a shunt for electrons directly to oxygen at the level of reduced flavin. This luciferase is an external flavin mono-oxygenase or mixed-function oxidase, electrons for reduction of flavin mononucleotide (FMN) are provided by the reducing power derived from the electron-transport pathway. The light-emitting reaction then proceeds via the reaction of molecular oxygen with reduced flavin to form an intermediate luciferase-flavin peroxy species, whose breakdown provides energy sufficient to leave one of the products in an electronically excited singlet state, with subsequent light emission. The bacterial (luciferase-bound) peroxide chromophore, which has been isolated and characterized, provides a model in this respect for the different bioluminescent reactions.

The Red Absorbing Flavin Species in the Reaction of Bacterial Luciferase with FMNH2 and O2

The reaction of luciferase-bound Z is known to result in the formation of a long-lived intermedlate in the bioluminescent reaction (1). This intermediate was isolated and ,haracterized as the luciferase-peroxyflavin (2), whose struc~ture was later shown to be the flavin 4a-substituted peroxyadduct (3). In the earlier work this peroxy intermediate had been shown to exhibit a single peak at about 370 rum, a shoulder a-t about 460 run, the absorption tailing off around 500 rum, with none above 520 run. In more recent publications,however (4,5), it has been reported that the reaction of the luciferase-bound reduced flavin mononucleotide with O2 also results in the appearance