Firefly Luciferins

Later, fireflv oxyluciferin was successfully synthesi2ed (403. 408) and has been isolated and identified in firefly lanterns (luciola cruaciata) after the lanterns were treated with pyridine and acetic anhydride to prevent decomposition (409). In 1972, Suzuki and Goto firmly established that oxyluciferin is involved in the bioluminescence of firefly lanterns and in the chemiluminescence of firefly luciferin (403. 410).. A. mechanism involving a four-membered ring cyclic peroxide has been proposed for the reaction (406. 411). However, it was not confirmed by 0 -labelinE experiments (412). 

Firefly. Firefly luciferase (EC 1.13.12.7) is a homodimeric enzyme (62 kDa subunit) that has binding sites for firefly luciferin and Mg ATP . Amino acid sequence analysis has iadicated that beetle luciferases evolved from coen2yme A synthetase (206). Firefly bioluminescence is the most efficient bioluminescent reaction known, with Qc reported to be 88% (5), and at 562 nm (56). At low pH and ia the presence of certain metal ions (eg, Pb ", ... 

A widely prescribed drug for the treatment of gastric ulcers with the generic name cimetidine is a synthetic imidazole derivative. Firefly luciferin is a thiazole derivative that is the naturally occuning light-emitting substance present in fireflies. 

Firefly luciferin is an exanple of an azole that contains a benzene ring fused to the five-rnernbered ring. Such structures are fairiy common. Another example is benzimidazole, present as a structural unit in vitfflnin B12. Some compounds related to benzimidazole include purine and its fflnino-substituted derivative adenine, one of the so-called heterocyclic bases found in DNA and RNA (Chapter 28). 

Fig. 1.3 Absorption spectra of firefly luciferin at pH 7.0 or below (solid line, Xmax 327-328 nm) and at pH higher than 9.0 (dashed line, Amax 381-384 nm). Reproduced from McElroy and Seliger, 1961, with permission from the Johns Hopkins University Press.

Fig. 1.4 Absorption spectrum of a spent luminescence solution of firefly luciferin containing luciferase-oxyluciferin after dialysis in 0.1 M potassium phosphate, pH 7.8. Replotted from the data of Gates and DeLuca, 1975, with permission from Elsevier.

Fig. 1.5 Fluorescence emission spectrum of the luciferase-oxyluciferin complex in the same solution as in Fig. 1.4 (solid line), compared with the luminescence spectrum of firefly luciferin measured in glycylglycine buffer, pH 7.6 (dotted line). The former curve from Gates and DeLuca, 1975 the latter from Selinger and McElroy, 1960, both with permission from Elsevier.

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). 

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.

Bioluminescence of firefly luciferin can produce a wide range of colors when catalyzed by different luciferases obtained from various species of fireflies, with their emission maxima ranging from 535 nm (yellow-green) to 638 nm (red). Apparently, each spectrum is emitted from a single emitting species they are not the composites of the yellow-green peak and the red peak (Seliger and McElroy, 1964). 

In the luminescence reaction of firefly luciferin (Fig. 1.12), one oxygen atom of the product CO2 is derived from the molecular oxygen while the other originates from the carboxyl group of luciferin. In the chemiluminescence reaction of an analogue of firefly luciferin in DMSO in the presence of a base, the analysis of the product CO2 has supported the dioxetanone pathway (White et al., 1975). 

The bioluminescence systems of Phengodidae (railroad worms) and Elateroidae (click beetles) are basically identical to that of Lampyridae (fireflies), requiring firefly luciferin, ATP, Mg2+ and a luciferase for light emission. However, there seem to be some differences. Viviani and Bechara (1995) reported that the spectra of the luminescence reactions measured with the luciferases of Brazilian fireflies (6 species) shift from the yellow-green range to the red range with lowering of the pH of the medium, like in the case of the Photinus pyralis luciferase (see Section 1.1.5), whereas the spectra... 

The order Diptera (flies) contains the glow-worms Arachnocampa and Orfelia. The bioluminescence systems of dipterans do not utilize firefly luciferin in their light-emitting reactions, differing from the bioluminescence systems of coleopterans. In dipterans, it is extremely intriguing that the bioluminescence system of Arachnocampa appears different from that of Orfelia-. the former luminescence is activated by ATP, whereas the latter luminescence is stimulated by DTT but not by ATP. 

One is the concerted decomposition of a dioxetanone structure that is proposed for the chemiluminescence and bioluminescence of both firefly luciferin (Hopkins et al., 1967 McCapra et al., 1968 Shimomura et al., 1977) and Cypridina luciferin (McCapra and Chang, 1967 Shimomura and Johnson, 1971). The other is the linear decomposition mechanism that has been proposed for the bioluminescence reaction of fireflies by DeLuca and Dempsey (1970), but not substantiated. In the case of the Oplopborus bioluminescence, investigation of the reaction pathway by 180-labeling experiments has shown that one O atom of the product CO2 derives from molecular oxygen, indicating that the dioxetanone pathway takes place in this bioluminescence system as well (Shimomura et al., 1978). It appears that the involvement of a dioxetane intermediate is quite widespread in bioluminescence. 

Bitler, B., and McElroy, W. D. (1957). The preparation and properties of crystalline firefly luciferin. Arch. Biochem. Biophys. 72 358-368. 

Bowie, L. J. (1978). Synthesis of firefly luciferin and analogs. Method. Enzymol. 57 15-28. 

Branchini, B. R. (2000). Chemical synthesis of firefly luciferin analogs and inhibitors. Method. Enzymol. 305 188-195. 

Morton, R. A., Hopkins, T. A., and Seliger, H. H. (1969). The spectroscopic properties of firefly luciferin and related compounds. An approach to product emission. Biochemistry 8 1598-1607. 

Suzuki, N., and Goto, T. (1971). Firefly bioluminescence. II. Identification of 2-(6 -hydroxy benzothiazol-2 -yl)4-hydroxythiazol as a product in the bioluminescence of firefly lanterns and as a product in the chemiluminescence of firefly luciferin in DMSO. Tetrahedron Lett. 22 2021-2024. 

Tsuji, F. I., et al. (1977). Mechanism of the enzyme-catalyzed oxidation of Cypridina and firefly luciferins studied by means of 17C>2 and H2lsO. Biochem. Biophys. Res. Commun. 74 606-613. 

White, E. H., Rapaport, E., Seliger, H. H., and Hopkins, T. A. (1971). The chemi- and bioluminescence of firefly luciferin an efficient chemical production of electoronically excited states. Bioorg. Chem. 1 92-122. 

D-Luciferin, 4 See Firefly luciferin L-Luciferin, 4 Luciferin binding protein dinoflagellates, 264, 265 Luciferin-luciferase cross-reaction, 324 Luciferins, xix-xxi, 340-342 coelenterazine, 159-179 Cypridina luciferin, 55-62, 160,... 

Quantula (Dyakia), 180, 334 Quantum yield, xvi, 361, 362 aequorin, 104, 106, 110 aldehydes in bacterial bioluminescence, 36, 41 Chaetopterus photoprotein, 224 coelenterazine, 85, 143, 149 Cypridina luciferin, 69-71 definition, xvi, 361 Diplocardia bioluminescence, 242 firefly luciferin, 12 fluorescent compound F, 73 Latia luciferin, 190 pholasin, 197 PMs, 286... 

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