Mechanisms of the Bioluminescence

In the postulated bioluminescence mechanism, firefly luciferin is adenylated in the presence of luciferase, ATP and Mg2+. Luciferyl adenylate in the active site of luciferase is quickly oxygenated at its tertiary carbon (position 4), forming a hydroperoxide intermediate (A). 

Because luciferyl adenylate emitted a red chemiluminescence in the presence of base, coinciding with the red fluorescence of 5,5-dimethyloxylucferin, the keto-form monoanion Cl in its excited state is considered to be the emitter of the red light. Thus, the emitter of the yellow-green light is probably the enol-form dianion C2 in its excited state, provided that the enolization takes place within the life-time of the excited state. Although the evidence had not been conclusive, especially on the chemical structures of the light emitters that emit two different colors, the mechanism shown in Fig. 1.12 was widely believed and cited until about 1990. 

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Fig. 1.12 Mechanism of the bioluminescence reaction of firefly luciferin catalyzed by firefly luciferase. Luciferin is probably in the dianion form when bound to luciferase. Luciferase-bound luciferin is converted into an adenylate in the presence of ATP and Mg2+, splitting off pyrophosphate (PP). The adenylate is oxygenated in the presence of oxygen (air) forming a peroxide intermediate A, which forms a dioxetanone intermediate B by splitting off AMP. The decomposition of intermediate B produces the excited state of oxyluciferin monoanion (Cl) or dianion (C2). When the energy levels of the excited states fall to the ground states, Cl and C2 emit red light (Amax 615 nm) and yellow-green light (Amax 560 nm), respectively.

Contrary to the dioxetanone pathway, DeLuca and Dempsey (1970) proposed a mechanism of the bioluminescence reaction that involves a multiple linear bond cleavage of luciferin peroxide... 

Fig. 8.9 Possible mechanisms of the bioluminescence reaction of dinoflagellate luciferin, based on the results of the model study (Stojanovic and Kishi, 1994b Stojanovic, 1995). The luciferin might react with molecular oxygen to form the luciferin radical cation and superoxide radical anion (A), and the latter deproto-nates the radical cation at C.132 to form (B). The collapse of the radical pair might yield the excited state of the peroxide (C). Alternatively, luciferin might be directly oxygenated to give C, and C rearranges to give the excited state of the hydrate (D) by the CIEEL mechanism. Both C and D can be the light emitter.

Ohmiya, Y., and Hirano, T. (1996). Shining the light the mechanism of the bioluminescence reaction of calcium-binding photoproteins. Chem. Biol. 3 337-347. 

Shimomura, O., Masugi, T., Johnson, F. H., and Haneda, Y. (1978). Properties and reaction mechanism of the bioluminescence system of the deep-sea shrimp Oplophorus gracilorostris. Biochemistry 17 994-998. 

Shimomura, O., T. Masugi, F. H. Johnson, and Y. Haneda Properties and Reaction Mechanism of the Bioluminescent System of the Deep-Sea Shrimp Oplophorus gracilorostris. Biochemistry 17, 994 (1978). 

Orlova et al. (2003) theoretically studied the mechanism of the firefly bioluminescence reaction on the basis of the hybrid density functional theory. According to their conclusion, changes in the color of light emission by rotating the two rings on the 2-2 axis is unlikely, whereas the participation of the enol-forms of oxyluciferin in bioluminescence is plausible but not essential to explain the multicolor emission. They predicted that the color of the bioluminescence depends on the polarization of the oxyluciferin molecule (at its OH and O-termini) in the microenvironment of the luciferase active site the... 

Fig. 2.1 Mechanism of the bacterial bioluminescence reaction. The molecule of FMNH2 is deprotonated at N1 when bound to a luciferase molecule, which is then readily peroxidized at C4a to form Intermediate A. Intermediate A reacts with a fatty aldehyde (such as dodecanal and tetradecanal) to form Intermediate B. Intermediate B decomposes and yields the excited state of 4a-hydroxyflavin (Intermediate C) and a fatty acid. Light (Amax 490 nm) is emitted when the excited state of C falls to the ground state. The ground state C decomposes into FMN plus H2O. All the intermediates (A, B, and C) are luciferase-bound forms. The FMN formed can be reduced to FMNH2 in the presence of FMN reductase and NADH.

Fig. 3.3.4 Reaction mechanism of the coelenterazine bioluminescence showing two possible routes of peroxide decomposition, the dioxetanone pathway (upper route) and linear decomposition pathway (lower route). The Oplopborus bioluminescence takes place via the dioxetanone pathway. The light emitter is considered to be the amide-anion of coelenteramide (see Section 5.4).

Fig. 4.6.2 A scheme showing the mechanism of the Renilla bioluminescence, and the chemical structures of coelenterazine derivatives involved.

Fig. 6.3.5 A reaction scheme proposed by Tsuji (2002) for the Watasenia bioluminescence. The proposed mechanism involves the adenylation of luciferase-bound luciferin by ATP, like in the bioluminescence of fireflies. However, the AMP group is split off from luciferin before the oxygenation of luciferin, differing from the mechanism of the firefly bioluminescence. Thus the role of ATP in the Watasenia bioluminescence reaction remains unclear. Reproduced with permission from Elsevier.

Harvey (1952) demonstrated the luciferin-luciferase reaction with O. phosphorea collected at Nanaimo, British Columbia, Canada, and with O. enopla from Bermuda. McElroy (1960) partially purified the luciferin, and found that the luminescence spectrum of the luciferin-luciferase reaction of O. enopla is identical to the fluorescence spectrum of the luciferin (A.max 510 nm), and also that the luciferin is auto-oxidized by molecular oxygen without light emission. Further investigation on the bioluminescence of Odontosyllis has been made by Shimomura etal. (1963d, 1964) and Trainor (1979). Although the phenomenon is well known, the chemical structure of the luciferin and the mechanism of the luminescence reaction have not been elucidated. 

Deng, L., et al. (2004b). Crystal structure of a Ca2+-discharged photoprotein Implications for mechanisms of the calcium trigger and bioluminescence. J. Biol. Chem. 279 33647-33652. 

Eberhard, A., and Hastings, J. W. (1972). A postulated mechanism for the bioluminescent oxidation of reduced flavin mononucleotide. Biochem. Biophys. Res. Commun. 47 348-353. 

Eckstein, J. W., Hastings, J. W., and Ghisla, S. (1993). Mechanism of bacterial bioluminescence. 4a,5-Dihydroflavin analogs as models for luciferase hydroperoxide intermediates and the effect of substituents at the 8-position of flavin on luciferase kinetics. Biochemistry 32 404 111. 

Hart, R. C., Stempel, K. E., Boyer, P. D., and Cormier, M. J. (1978). Mechanism of the enzyme-catalyzed bioluminescent oxidation of coelenterate-type luciferin. Biochem. Biophys. Res. Commun. 81 980-986. 

C NMR spectroscopy has been used to establish the structures of intermediates formed during the photooxygenation of 13C-labeled derivatives of 64 related to bioluminescent luciferins <1996T12061>. The mechanism of the formation of 3-oxo derivatives of 64 related to the chemistry of bioluminescence has been studied by low-temperature 13C (together with variable temperature proton) NMR spectroscopy <1997J(P2)1831>. The 13C and 1SN... 

Fig. 26 Mechanism of the ATP- and Mg2+-dependent firefly luciferase catalyzed bioluminescence oxidation reaction of D-luciferin (d-LH2) to oxyluciferin (oxy-L)...

Figure 5.26 Mechanism of a bioluminescence reaction. A luciferin is oxidized in the presence of an enzyme (luciferase Lz) and adenosine triphosphate, ATP...

Although certain marine organisms produce light when mechanically perturbed, this phenomenon has been used little, and the distribution and activities of the bioluminescent organisms in situ are little known. A few concerted efforts (3-9) showed that bioluminescence is observed almost everywhere ships go that is, the phenomenon is nearly ubiquitous and highly variable. 

Now we focus on the structural analysis of symplectin active site and the molecular mechanism of symplectin bioluminescence. ... 

Studying the mechanism of the effects of heavy atoms on metabolic processes is an important task for developing methods to monitor the toxic effects of halides. Bioluminescent reactions are convenient models for such studies because of simple and prompt recording of the rate of enzymatic process. 

Several mechanisms have been proposed to explain the variations of the bioluminescence color for native and mutant luciferases. According to White at al1 changes in bioluminescence spectra are the result of keto-enol tautomerization of oxyluciferin (LO). The efficiency of this process depends on a correct location of the B, and B2 bases in proximity of the thiazole ring for effective transformation of the ketone form of LO (L0=0) to the enol (LO-OH) which can interact with the B3 base to form enolate-ion (LO-O ). When the Bi base is absent or protonated (e g. at pH < 6.0) bioluminescence of the L0=0 will be observed with Xmax in the red region of the spectrum. At intermediate pH all forms L0=0, LO-OH and (LO-O ) - will be observed in the bioluminescence spectra.2... 

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