EVIDENCE FOR DE-NOVO BIOSYNTHESIS OF COELENTERAZINE IN THE BIOLUMINESCENT MIDWATER SHRIMP, SYSTELLASPIS-DEBILIS

Coelenterazine chemiluminescence is now established as the most common chemistry responsible for bioluminescence in the sea, being found in seven phyla. However, the organisms which synthesize coelenterazine ha ve yet to be identified. In order to determine whether the luminous mi dwater shrimp Systellaspis debilis (A. Milne Edwards) (Arthropoda: Dec apoda) is capable of luciferin biosynthesis, a developmental series of eggs was assayed for its luciferin, coelenterazine. The advantages of this system are that S. debilis eggs are autonomous and therefore hav e no external nutrient supply, the embryos can be ranked for developme ntal stage and the large egg size allows clutch numbers to be determin ed accurately. Recombinant apo-aequorin, which requires coelenterazine for luminescence, was used to quantify coelenterazine during the deve lopmental sequence. An increase of almost two orders of magnitude was detected in coelenterazine content per egg between the first and final stage of development (mean values of 1 pmol and 71 pmol). This demons trates de novo biosynthesis of coelenterazine for the first time.