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Table 2. Rate constants of coelenterazine, the amino acids constituting the proposed tripeptide precursor and two important cellular antioxidants with singlet oxygen ('02) and superoxide anion (02' >)

Table 2 Rate constants of coelenterazine, the amino acids constituting the proposed tripeptide precursor and two important cellular antioxidants with singlet oxygen ('02) and superoxide anion (02' >)

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Fig. 1. Structure of several luciferins found in bioluminescent organisms. (A) Coelenterazine, (B) Vargula luciferin, (C) Diplocardia luciferin, (D) Latia luciferin, (E) Coleoptera luciferin and (F) dinoflagellate luciferin. One of the most striking characteristics of bioluminescence is the very high diversity of mechanisms, structures and functions that bioluminescent organisms have achieved. This is well illustrated by the many different chemistries, reflected by the occurrence of various photogenic substrates (Fig. 1), occurring in bioluminescence. The diversity of chemistries involved in bioluminescent mechanisms renders generalisations hazardous, and attempts to represent bioluminescent reactions schematically have led to confusion. Owing to this high diversity, the safest way to define a bioluminescent reaction would be ‘a reaction that produces ecologically functional light occurring in a living organism’. Indeed, light emission is not restricted to bioluminescent organisms, but probably occurs in any tissue of any organism as a by-product of metabolic reactions and oxidations (Murphy and Sies, 1990). The requirement for an enzyme physically interacting with the luciferin is not universal. In the boring clam Pholas dactylus, no binding of the luciferin to the luciferase occurs during the light-emitting reaction (Michelson, 1978). Shimomura et al. (1993) suggested that some luminescent fungi might lack a proper luciferase enzyme entirely.
Fig. 1. Structure of several luciferins found in bioluminescent organisms. (A) Coelenterazine, (B) Vargula luciferin, (C) Diplocardia luciferin, (D) Latia luciferin, (E) Coleoptera luciferin and (F) dinoflagellate luciferin. One of the most striking characteristics of bioluminescence is the very high diversity of mechanisms, structures and functions that bioluminescent organisms have achieved. This is well illustrated by the many different chemistries, reflected by the occurrence of various photogenic substrates (Fig. 1), occurring in bioluminescence. The diversity of chemistries involved in bioluminescent mechanisms renders generalisations hazardous, and attempts to represent bioluminescent reactions schematically have led to confusion. Owing to this high diversity, the safest way to define a bioluminescent reaction would be ‘a reaction that produces ecologically functional light occurring in a living organism’. Indeed, light emission is not restricted to bioluminescent organisms, but probably occurs in any tissue of any organism as a by-product of metabolic reactions and oxidations (Murphy and Sies, 1990). The requirement for an enzyme physically interacting with the luciferin is not universal. In the boring clam Pholas dactylus, no binding of the luciferin to the luciferase occurs during the light-emitting reaction (Michelson, 1978). Shimomura et al. (1993) suggested that some luminescent fungi might lack a proper luciferase enzyme entirely.
Fig. 2. Schematic illustration of a bioluminescent reaction. Steps and components common to all known systems are underlined.
Fig. 2. Schematic illustration of a bioluminescent reaction. Steps and components common to all known systems are underlined.
Table 1. Turnover rates of oxygenases
Table 1. Turnover rates of oxygenases
Fig. 3. Cytoprotective effect of coelenterazine on human fibroblasts (MRC-5) subjected to oxidative stress induced by 10~+mol17 tert- butyl-hydroperoxide. Survival is expressed as a percentage of that measured in control cells unexposed to the stress-inducing agent. Values are means + s.E.M. (N=6). Asterisks indicate values siginificantly different from the value in the absence of coelenterzine; *P <0.05, **P <0.01.
Fig. 3. Cytoprotective effect of coelenterazine on human fibroblasts (MRC-5) subjected to oxidative stress induced by 10~+mol17 tert- butyl-hydroperoxide. Survival is expressed as a percentage of that measured in control cells unexposed to the stress-inducing agent. Values are means + s.E.M. (N=6). Asterisks indicate values siginificantly different from the value in the absence of coelenterzine; *P <0.05, **P <0.01.
The test used emulsified linoleate incubated at 37°C with 1.6 mmol 1+ AAPH [azo-bis (2-amidinopropane hydrochloride)] as described by Saija et al. (1995). a
The test used emulsified linoleate incubated at 37°C with 1.6 mmol 1+ AAPH [azo-bis (2-amidinopropane hydrochloride)] as described by Saija et al. (1995). a
Table 4. Possible relationships between bioluminescent systems and antioxidative mechanisms Besides the direct involvement of activated species of oxygen, some systems are linked either by the catalytic activity of the luciferase towards reactive oxygen species, or by the involvement of cofactors linked to oxidative stress (see text for explanations and references).
Table 4. Possible relationships between bioluminescent systems and antioxidative mechanisms Besides the direct involvement of activated species of oxygen, some systems are linked either by the catalytic activity of the luciferase towards reactive oxygen species, or by the involvement of cofactors linked to oxidative stress (see text for explanations and references).
MDA), an oxidation product 0 mixing a sample of the medium Fig. 4. Catabolic activity of bacterial luciferase towards fatty acid aldehydes produced during lipid peroxidation (A. Coutelier and J.-F. Rees, unpublished results). Rat hepatocytes were treated for 2h in the presence of 10 mol 17 tert-butylhydroperoxide. Malondialdehyde f unsaturated fatty acids, was assayed in the culture medium (0). In parallel, the luminescence elicited by with bacterial luciferase and FMNH2 according to the method of M expressed in pmol tetradecanal intensity (@). orse et al. 1986) was measured and required to elicit the same luminous
MDA), an oxidation product 0 mixing a sample of the medium Fig. 4. Catabolic activity of bacterial luciferase towards fatty acid aldehydes produced during lipid peroxidation (A. Coutelier and J.-F. Rees, unpublished results). Rat hepatocytes were treated for 2h in the presence of 10 mol 17 tert-butylhydroperoxide. Malondialdehyde f unsaturated fatty acids, was assayed in the culture medium (0). In parallel, the luminescence elicited by with bacterial luciferase and FMNH2 according to the method of M expressed in pmol tetradecanal intensity (@). orse et al. 1986) was measured and required to elicit the same luminous
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