Bioconcentration mechanism of selenium by a coccolithophorid, Emiliania huxleyi
Bioconcentration mechanism of selenium by a coccolithophorid, Emiliania huxleyi
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DOI：
10.1093/pcp/pch164
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发表时间：
2004-10-01
影响因子：
4.9
通讯作者：
Shiraiwa, Y
中科院分区：
文献类型：
--
作者：
Obata, T;Araie, H;Shiraiwa, Y
利用[Se-75]亚硒酸盐研究了球石藻Emiliania huxleyi对必需元素硒的吸收和富集。Se-75摄取的时间过程显示出双相模式，即初级阶段和随后的次级阶段。初级阶段和次级阶段是由于快速的亚硒酸盐摄取过程，在2分钟内达到一个稳定的水平和缓慢的硒积累过程，继续在一个恒定的速率为4小时或更长时间，分别。动力学分析表明，亚硒酸盐的吸收过程包括两个组成部分，一个饱和和一个线性相关的底物浓度。酸克雷的饱和组分是29.8 nM亚硒酸盐;该组分的摄取活性被抑制ATP生物合成的抑制剂，这表明亚硒酸盐摄取是由高亲和力，主动运输系统驱动。在细胞与[Se-75]亚硒酸盐孵育6小时期间，70%的细胞内Se-75被掺入到低分子量化合物（LMCs）中，17%被掺入到蛋白质中，但[Se-75]亚硒酸盐几乎检测不到。脉冲追踪实验表明，硒-75已积累在LMCs转移到蛋白质。当氨基酸和蛋白质的合成分别受到抑制时，Se-75掺入LMCs和蛋白质的量减少。这些结果表明，E. Huxleyi迅速吸收亚硒酸盐，填充小的细胞内池。然后，含硒的LMCs立即从亚硒酸盐合成，产生一个LMCs池，然后代谢为硒蛋白。
We investigated the uptake and bioconcentration of the essential element selenium by a coccolithophorid, Emiliania huxleyi, using [Se-75]selenite. The time course of Se-75 uptake showed a biphasic pattern, namely a primary phase and a subsequent secondary phase. The primary and secondary phases are due to a rapid selenite uptake process that attained a stationary level within 2 min and a slow Se-accumulation process that continued at a constant rate for 4 h or longer, respectively. Kinetic analysis revealed that the selenite uptake process consists of two components, one saturable and one linearly related to substrate concentration. The K. of the saturable component was 29.8 nM selenite; the uptake activity of this component was suppressed by inhibitors of ATP biogenesis, suggesting that selenite uptake is driven by a high-affinity, active transport system. During a 6-h incubation of cells with [Se-75]selenite, 70% of the intracellular Se-75 was incorporated into low-molecularmass compounds (LMCs), and 17% was incorporated into proteins, but [Se-75]selenite was barely detectable. A pulse-chase experiment demonstrated that the Se-75 that had accumulated in LMCs was transferred into proteins. When the syntheses of amino acids and proteins were each separately inhibited, Se-75 incorporation into LMCs and proteins was decreased. These results suggest that E. huxleyi rapidly absorbs selenite, filling a small intracellular pool. Then, Se-containing LMCs are immediately synthesized from the selenite, creating a pool of LMCs that are then metabolized to selenoproteins.