19 トビイカ生物発光機構の化学的研究(口頭発表の部)

抄録

In the squid luminescence in S. oualaniensis, the system requires molecular oxygen and monovalent cations (e.g. Na+, K+, etc.) for bioluminescence. We found that only a high molecular fraction (from gel filtration chromatography with Bio-gel P-6) emits light (470nm) by addition of KCl and O_2. When the homogenate was extracted only with MeOH (without acetone), dehydrocoelenterazine (1) was extracted, its amount being estimated about 20% from the total luminescent light. None of 1 nor 5 was, however, detected after luminescence (470nm) of the homogenate of the photogenic organs by addition of KCl, indicating that the bioluminescence of S. oualaniensis consumed dehydrocoelenterazine 1. Although dehydrocoelenterazine (1) itself does not exhibit any chemi-luminescence activity, some derivatives produced by addition (such as 4, 5, 6 etc.) should retain the activity. The dithiothreitol adduct to dehydrocoelenterazine, although existing only as equilibrium, in agreement with higher and longer luminescence activity of this squid as reported by Tsuji et al. Dehydrocoelenterazine absorbs long wavelength light to become reddish color, but the photogenic organ is not red but yellow-brown (identical with the acetone adduct 4), indicating that the existing conjugate system is broken. This phenomenon is interpreted by deconjugative addition of nucleophile in protein (e.g. a functional residue on lysine, cysteine etc.). These facts led us to conclude that dehydrocoelenterazine 1 exists as adduct as 5. In conclusion, the possibility of the dehydrocoelenterazine adduct as the luciferin of S. oualaniensis bioluminescence system becomes apparent through the current studies.