Stimulatory effect of sulphide on thiotaurine synthesis in three hydrothermal-vent species from the East Pacific Rise
Stimulatory effect of sulphide on thiotaurine synthesis in three hydrothermal-vent species from the East Pacific Rise
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硫化物对东太平洋海隆三种热液喷口物种硫代牛磺酸合成的刺激作用
DOI：
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发表时间：
2003
影响因子：
2.8
通讯作者：
A. Fiala
中科院分区：
文献类型：
--
作者：
A. Pruski;A. Fiala
摘要海洋无脊椎动物和硫氧化细菌之间的共生关系是硫化物丰富环境中的一个共同特征，例如在热液喷口附近繁茂的环境中。虽然细菌内共生菌为寄主提供了毋庸置疑的营养优势，但它们的存在也需要对硫化物的运输和储存进行特殊的适应，硫化物是一种有效的有氧呼吸毒素。尽管已经描述了不同的机制，如硫化物与血清结合蛋白的可逆结合或其氧化为毒性较低的形式，但许多问题仍未得到解答。在过去的十年里，据报道，在热液喷口和冷渗漏的硫基共生体中，有大量的硫代牛磺酸，这是一种罕见的硫代氨基酸。硫代牛磺酸等化合物已知参与反式硫化反应，因此硫代牛磺酸参与了硫化物的代谢。本文介绍了来自东太平洋海隆的三种含硫氧化共生体的生物合成硫代牛磺酸的实验研究。这三种共生体分别是：丝孢霉、嗜热豆腐霉菌和厚厚裂头藻。在所有三个物种中，硫代牛磺酸的合成在体外都受到硫化物和硫代硫酸盐的刺激，嗜热杆菌中的硫代牛磺酸的合成也是如此。然而，似乎出现了几种不同的代谢途径，因为亚牛磺酸是双壳类贝类和嗜热双壳类中唯一的前体，而在厚皮双壳类中，硫代牛磺酸也是由牛磺酸产生的。次牛磺酸(NH2-CH2-CH2-SO2H)和硫代牛磺酸(NH2-CH2-CH2-SO2SH)是两种不含硫的氨基酸，其化学式仅相差一个硫原子。似乎硫代牛磺酸的合成程度强烈地依赖于这两种氨基酸之间的初始平衡，因为在初始硫代牛磺酸浓度最低的组织中发现了最强的硫代牛磺酸合成速率。此外，硫化物在无共生体的组织和甲烷营养贻贝的鳃中没有任何影响，这强化了硫代牛磺酸合成是对硫代营养生活方式的特定适应的假设。虽然亚牛磺酸和硫代牛磺酸的确切功能(即硫化物的运输和/或储存)尚未确定，但我们的结果有力地支持了这些游离氨基酸在热液喷口硫化物营养共生体中硫化物代谢中的普遍作用。
SUMMARY Symbiotic associations between marine invertebrates and sulphur-oxidising bacteria are a common feature in communities from sulphide-rich environments, such as those flourishing in the vicinity of hydrothermal vents. While the bacterial endosymbionts provide the host with an undoubted nutritional advantage, their presence also requires specific adaptations for the transport and storage of sulphide, which is a potent toxin of aerobic respiration. Although different mechanisms such as the reversible binding of sulphide to serum binding proteins or its oxidation to less toxic forms have been described, many questions still remained unanswered. In the last decade, large amounts of thiotaurine, an unusual sulphur-amino acid, have been reported in sulphur-based symbioses from hydrothermal vents and cold seeps. Compounds such as thiotaurine are known to take part in trans-sulphuration reactions, so the involvement of thiotaurine in sulphide metabolism has been suggested. We present here an experimental study on thiotaurine biosynthesis in three sulphur-oxidising symbiont-bearing species from the East Pacific Rise: the vesicomyid Calyptogena magnifica, the mytilid Bathymodiolus thermophilus and the vestimentiferan Riftia pachyptila. In all three species, thiotaurine synthesis is stimulated in vitro by an input of sulphide, as well as by thiosulphate in B. thermophilus. Several distinct metabolic pathways seem to occur, however, since hypotaurine is the only precursor in the bivalves C. magnifica and B. thermophilus, whereas thiotaurine is also produced from taurine in R. pachyptila. Hypotaurine (NH2-CH2-CH2-SO2H) and thiotaurine (NH2-CH2-CH2-SO2SH) are two free sulphur amino acids whose chemical formulae differ by only one atom of sulphur. It appears that the extent of thiotaurine synthesis is strongly dependent on the initial equilibrium between these two amino acids, since the strongest thiotaurine synthesis rates are found in tissues with the lowest initial thiotaurine concentration. Moreover, the lack of any effect of sulphide in symbiont-free tissues and in gills of the methanotrophic mussel Bathymodiolus childressi reinforces the assumption that thiotaurine synthesis is a specific adaptation to the thiotrophic mode of life. While the precise function (i.e. transport and/or storage of sulphide) of hypotaurine and thiotaurine has yet to be established, our results strongly support a general role for these free amino acids in the metabolism of sulphide in hydrothermal-vent thiotrophic symbioses.
酵母硫代硫酸还原酶的催化机制。
DOI：
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发表时间：
1983
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Chauncey,TR;Westley,J
通讯作者：
Westley,J