Pyrocystis lunula bioluminescence: physicochemical characterization of the luciferin precursor

The luminescence of the dinoflagellate Pyrocystis lunula is controlled by the reduction state of the luciferin precursor. This molecule (P630) is a chromopeptide more stable than luciferin in methanolic solutions at low temperature. Cations may oxidize P630 or cleave the bond between the peptidic chain and the extended tetrapyrrole. Reduction of P630 is performed enzymatically by a NAD(P)H-dependent oxidoreductase or chemically by 2-mercaptoethanol or dithiothreitol. The state of reduction is monitored by the absorption and fluorescence emission which reveal a conformational change of the chromopeptide depending on the pH. These data will be useful for forthcoming studies on intracellular reducing power regulation and luminescence rhythms of these cells.