Abstract
Marine luciferases are increasingly used as reporters to study gene regulation. These luciferases have utility in bioluminescent assay development, although little has been reported on their catalytic properties in response to substrate concentration. Here, we report that the two marine luciferases from the copepods, Gaussia princeps (GLuc) and Metridia longa (MLuc) were found, surprisingly, to produce light in a cooperative manner with respect to their luciferin substrate concentration; as the substrate concentration was decreased 10 fold the rate of light production decreased 1000 fold. This positive cooperative effect is likely a result of allostery between the two proposed catalytic domains found in Gaussia and Metridia. In contrast, the marine luciferases from Renilla reniformis (RLuc) and Cypridina noctiluca (CLuc) demonstrate a linear relationship between the concentration of their respective luciferin and the rate of light produced. The consequences of these enzyme responses are discussed.
Highlights
Luciferases, the enzymes responsible for the bioluminescence reaction, are present in multiple animal phyla and bacteria
In examining the detection limit of the marine luciferases for their luciferins, a fixed amount of luciferase was incubated with varying concentrations of its corresponding luciferin and the light generated was measured
The quantity of light generated in 10 seconds with RLuc was nearly linear with respect to the substrate over a 5 order of magnitude range of concentration: for every 10 fold decrease in coelenterazine concentration the light decreased about 10 fold
Summary
Luciferases, the enzymes responsible for the bioluminescence reaction, are present in multiple animal phyla and bacteria. The luciferases oxidize luciferins to produce light and the chemical nature of the luciferins can vary widely. Perhaps the best known are the ATP-dependent beetle luciferases that catalyze the oxidation of firefly luciferin in a photochemical reaction that has been widely used for the detection of low levels of ATP. Most marine luciferases do not use ATP, requiring only their luciferin and molecular oxygen as substrates with oxyluciferin, CO2 and light as products. Different species use different luciferins: coelenterazine is the cognate luciferin for Renilla, Gaussia and Metridia luciferases (RLuc, GLuc and MLuc, respectively), while cypridina luciferin is the cognate luciferin for Cypridina luciferase (CLuc) (Figure 1). The two chemically related luciferins share the common chromophore, imidazopyrazinone
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