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|All Authors / Contributors:||
Elodie Verhaeghe; Bernard Rousseau, (19..-.... ; chimiste).; Université de Paris-Sud. Faculté des Sciences d'Orsay (Essonne).
|Description:||1 vol. (307 p.) : ill. en noir et en coul. ; 30 cm.|
|Responsibility:||Elodie Verhaeghe ; sous la direction de Bernard Rousseau.|
Vanadium dependent-haloperoxidases (vHPOs) are supposed to be key-enzymes in the iodine metabolism of brown kelp (especially Laminariales). These enzymes are likely to be involved in the iodine uptake and in the emission of volatile iodinated compounds. In order to confirm this hypothesis, a strategy of reverse chemical genetics was performed in order to study the effect of the vHPO invalidation in vivo. We carried out a high-throughput screening (HTS) on the vanadium dependent-bromoperoxydase of Ascophyllum nodosum in order to identify specific inhibitors from a chemical library of 16480 compounds. Additional tests revealed that the selected hits are not inhibitors of the vBPO but are extremely reactive towards oxidized iodine species which were generated by the vHPOs. We showed that these molecules blocked the iodine uptake by the brown alga Laminaria digitata, which indirectly confirms the involvement of vHPOs in this mechanism. Besides, the tissue and subcellular iodine distributions in L. digitata were investigated by two micro-chemical imaging techniques : SIMS microprobe and proton microprobe. Our study clearly showed that iodine is stored in the peripheral tissue in the apoplastic compartment and not in intra-cellular structures, as previously proposed. This unexpected localisation raises new questions and new hypotheses on the mechanism of iodine storage in brown algal kelps. At the same time, we carried on studying the inhibitors of the iodine uptake in NIS-expressing cell lines. We carried out their synthesis, confirmed their biological activity and initiated the identification of their targeting proteins by photoaffinity labelling.