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COLIN

Iodine transfers in the coastal marine environment: the key role of brown algae and of their vanadium-dependent haloperoxidases.

Leblanc C, Colin C, Cosse A, Delage L, La Barre S, Morin P, Fievet B, Voiseux C, Ambroise Y, Verhaeghe E, Amouroux D, Donard O, Tessier E, Potin P.

Biochimie. 2006 Sep 18; [Epub ahead of print]

"Brown algal kelp species are the most efficient iodine accumulators among all living systems, with an average content of 1.0% of dry weight in Laminaria digitata, representing a ca. 30,000-fold accumulation of this element from seawater. Like other marine macroalgae, kelps are known to emit volatile short-lived organo-iodines, and molecular iodine which are believed to be a main vector of the iodine biogeochemical cycle as well as having a significant impact on atmospheric chemistry. Therefore, radioactive iodine can potentially accumulate in seaweeds and can participate in the biogeochemical cycling of iodine, thereby impacting human health. From a radioecological viewpoint, iodine-129 ((129)I, half-life of 1.6x10(7) years) is one of the most persistent radionuclide released from nuclear facilities into the environment. In this context, the speciation of iodine by seaweeds is of special importance and there is a need to further understand the mechanisms of iodine uptake and emission by kelps. Recent results on the physiological role and biochemistry of the vanadium haloperoxidases of brown algae emphasize the importance of these enzymes in the control of these processes."

The brown algal kelp Laminaria digitata features distinct bromoperoxidase and iodoperoxidase activities.

Colin C, Leblanc C, Wagner E, Delage L, Leize-Wagner E, Van Dorsselaer A, Kloareg B, Potin P.

J Biol Chem. 2003 Jun 27;278(26):23545-52. Epub 2003 Apr 15.

"Different haloperoxidases, one specific for the oxidation of iodide and another that can oxidize both iodide and bromide, were separated from the sporophytes of the brown alga Laminaria digitata and purified to electrophoretic homogeneity. The iodoperoxidase activity was approximately seven times more efficient than the bromoperoxidase fraction in the oxidation of iodide. The two enzymes were markedly different in their molecular masses, trypsin digestion profiles, and immunological characteristics. Also, in contrast to the iodoperoxidase, bromoperoxidases were present in the form of multimeric aggregates of near-identical proteins. Two full-length haloperoxidase cDNAs were isolated from L. digitata, using haloperoxidase partial cDNAs that had been identified previously in an Expressed Sequence Tag analysis of the life cycle of this species (1). Sequence comparisons, mass spectrometry, and immunological analyses of the purified bromoperoxidase, as well as the activity of the protein expressed in Escherichia coli, all indicate that these almost identical cDNAs encode bromoperoxidases. Haloperoxidases form a large multigenic family in L. digitata, and the potential functions of haloperoxidases in this kelp are discussed."

Caracterisation biochemique et moleculaire des haloperoxydases dependantes du vanadate chez l'algue brune Laminaria digitata

Colin C

Doctoral Dissertation, 2004.  [in French]

[English abstract]

"As well as the particular and specific role of vIPOs [vanadium-dependent iodoperoxidase] in the absorption of iodine, members of both vHPO [vanadium-dependent haloperoxidase] families seem to be involved in defence mechanisms and some stress induced responses and particularly under oxidative stress conditions.  Within this context, they play a direct role as anti-oxidative enzymes, by consuming hydrogen peroxide.  They may also synthesize halogenated compounds which are considered as defence mechanisms.  We have also established the existence of some links between their induction with the oxylin pathway."

Structure of algal-born phenolic polymeric adhesives.

Bitton R, Ben-Yehuda M, Davidovich M, Balazs Y, Potin P, Delage L, Colin C, Bianco-Peled H.

Macromol Biosci. 2006 Sep 15;6(9):737-46.

[abstract only]

"Adhesive materials extracted from the brown alga Fucus serratus are composed of phenolic polymer, alginate, and CaCl2. The phenolic polymer undergoes an oxidation reaction in the presence of bromoperoxidase, KI, and H2O2. The nanostructure of the adhesive was investigated using small angle X-ray scattering, light scattering, and cryo- transmission electron microscopy experiments. These have shown that the phenolic polymer undergoes self-assembly and forms flexible chain-like objects. Oxidation or adding alginate does not alter this structure. However, once calcium ions are added, a rigid network is formed. Presumably, this network is responsible for the cohesive strength of the glue."

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