CIRCADIAN RHYTHMICITY OF TRYPTOPHAN-HYDROXYLASE IN THE MARINE DINOFLAGELLATE GONYAULAX-POLYEDRA STEIN AND THE ROLE OF TRYPTOPHAN HYDROXYLATION IN BIOLUMINESCENCE
S. Burkhardt et R. Hardeland, CIRCADIAN RHYTHMICITY OF TRYPTOPHAN-HYDROXYLASE IN THE MARINE DINOFLAGELLATE GONYAULAX-POLYEDRA STEIN AND THE ROLE OF TRYPTOPHAN HYDROXYLATION IN BIOLUMINESCENCE, Comparative biochemistry and physiology. B. Comparative biochemistry, 115(3), 1996, pp. 411-416
In the bioluminescent dinoflagellate Gonyaulax polyedra, tryptophan hy
droxylase activity exhibits a circadian rhythm of high amplitude, whic
h persists in constant light. The maximum is found in the middle of ph
otophase. Melatonin or exposure to a decreased temperature (15 degrees
C), a treatment leading to melatonin accumulation, suppresses tryptop
han hydroxylase activity. 5-Hydroxytryprophan, but not tryptophan, sti
mulates bioluminescence. The dosage dependence of this effect of 5-hyd
roxytryptophan is similar to that of its metabolite serotonin. These a
ctions seem to be due to the further conversion to a much more potent
metabolite, 5-methoxytryptamine. Inhibition of tryptophan hydroxylase
by p-chlorophenylalanine, p-fluorophenylalanine or 5-fluorotryptophan
decreases light emission. This inhibition can be overcome by addition
of various indolic metabolites originating from the tryptophan hydroxy
lation pathway, in particular, 5-hydroxycryptophan, serotonin, melaton
in and 5-methoxytryptamine. Copyright (C) 1996 Elsevier Science Inc.