The roles of the two highly unstable components F and P involved in the bioluminescence of euphausiid shrimps.
Bioluminescence of euphausiids takes place when a fluorescent tetrapyrrole F and a highly unstable protein P react in the presence of oxygen. A previous study on the euphausiid Meganyctiphanes norvegica indicated that F acts as a catalyst and P is consumed in the luminescence reaction, differing from the luminescence system of dinoflagellates in which a tetrapyrrole luciferin, nearly identical to F, is enzymatically oxidized in the presence of dinoflagellate luciferase. In the present study, P was extracted from Euphausia pacifica as well as from M. norvegica, then purified separately by affinity chromatography on a column of biliverdin-Sepharose 4B, completing the whole process in less than 5 h. The samples of P obtained from both species had a molecular weight of 600,000, a purity of about 80%, and a specific activity 50-100 times greater than that previously found. The activity of P rapidly decreased in solutions, even at 0 degrees C, and the inactivation of P derived from M. norvegica was more than four times faster than that derived from E. pacifica. The kinetics of the luminescence reaction was investigated with F and P whose concentrations were systematically varied. The reaction was characteristically slow and involved two different reaction rates; the turnover number at 0 degrees C was 30/h for the initial 20 min and 20/h after the initial 1 h. The total light emitted in a 50-h period indicated that the bioluminescence quantum yield of F was about 0.6 at 0 degrees C, and P recycled many times in the luminescence reaction. Thus, the present results conclusively show that F is a luciferin and P is a luciferase of an unusually slow-working type, contrary to early report.
Shimomura
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Marine Biological Laboratory, Woods Hole, MA 02543, USA.
D000818:Animals; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D033364:Decapoda / Q000378:metabolism*; D004795:Enzyme Stability; D049454:Firefly Luciferin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008156:Luciferases / Q000302:isolation & purification / Q000378:metabolism; D008163:Luminescent Measurements; D015394:Molecular Structure; D008970:Molecular Weight; D011789:Quantum Theory
D049454:Firefly Luciferin; D008156:Luciferases