P-23 海綿Axinyssa aculeataより得られた新規長鎖ポリアミンの骨片形成への関与(ポスター発表の部)

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Long chain polyamines (LCPA), which have been known exclusively in silica wall of diatoms in nature, are thought to play a central role in diatom's silica deposition. In the present study, however, we identified LCPA for the first time from the marine sponge Axinyssa aculeata and named LCPA-Aa. The LCPA-Aa was obtained as a mixture of oligo-propaneamine sulfates of 5 to 15 repeating units (ru). It has been reported that LCPA of diatoms mediate precipitation of silica in a multivalent anion-dependent manner, in that the multivalent anions are important in facilitating the formation of large aggregate of polyamines via electrostatic interaction. Eventually the aggregate grows large enough to give rise macroscopic phase separation. Interaction between the aggregate and oligosilicic acid is of a crucial step for further "hardening" of silica precipitation. Formation of large aggregate of LCPA-Aa was demonstrated by ^1H NMR titration experiment with Ba^<2+> as significant signal broadening was observed when the ratio of sulfate ion [SO_4^<2->] and the propane amine repeating unit [ru] became about 0.36 ([SO_4^<2->]/[ru]). This value was similar to the ratio where macroscopic phase separation of polyallylamine takes place. Above results suggested that LCPA-Aa possibly involve in precipitation of silica, i.e. spicule formation, in the sponge. In fact, LCPA was also isolated from the HF-treated spicules of this sponge. We thus tested the ability of LCPA-Aa to precipitate monosilicic acid into silica in vitro. Silica precipitation was formed at pH6.5, the physiological pH of sponge cellular extract, in the presence of LCPA-Aa while no precipitation formed in the solution without LCPA-Aa. Although biologically controlled silica deposition in sponges is known to be mediated by a protein called silicatein, our results allow proposing additional mechanism on the biomineralization process in the sponges.
天然有機化合物討論会の論文
2006-09-15

P-23 海綿Axinyssa aculeataより得られた新規長鎖ポリアミンの骨片形成への関与(ポスター発表の部)

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