| Bioluminescent organisms are widely distributed in nature and comprise a remarkably diverse set of species (20, 59, 60, 62, 81). Among the light-emitting species are bacteria, dinoflagellates, fungi, fish, insects, shrimp, and squid. This set of organisms includes terrestrial, freshwater, and marine species from almost 50% of the different phyla in the animal and plant kingdoms (59). The enzymes that catalyze the bioluminescence reactions in these organisms are called luciferases, and in most cases the substrates are designated as luciferins (34). However, consistent with the apparent absence of a strong evolutionary relationship between many of the light-emitting systems, significant differences exist between the bioluminescence reactions as well as the structures of the luciferases (enzymes) and luciferins (substrates) from different organisms. Aside from light emission, only the requirement for 02 for the bioluminescence reactions has been clearly recognized as a common feature of the luminescence systems. This property was initially recognized more than three centuries ago by Robert Boyle, who demonstrated that air (02) was required for light emission by rotting wood containing luminescent fungi or bacteria (16). A little more than two centuries later, Dubois demonstrated, by performing classic in vitro experiments with hot- and cold-water extracts from the luminous fire beetle and the boring clam, the requirements for luciferase, luciferin(s), and oxygen in these luminescence systems (34). |