Laboratory of Chemical Toxicology and Environmental Health, Showa Pharmaceutical University, 3-3165 Higashi-Tamagawagakuen, Machida, Tokyo 194-8543, Japan.
Metallomics. 2013 Sep;5(9):1215-24. doi: 10.1039/c3mt00108c.
Tellurium (Te) is a widely used metalloid in industry because of its unique chemical and physical properties. However, information about the biological and toxicological activities of Te in plants and animals is limited. Although Te is expected to be metabolized in organisms via the same pathway as sulfur and selenium (Se), no precise metabolic pathways are known in organisms, particularly in plants. To reveal the metabolic pathway of Te in plants, garlic, a well-known Se accumulator, was chosen as the model plant. Garlic was hydroponically cultivated and exposed to sodium tellurate, and Te-containing metabolites in the water extract of garlic leaves were identified using HPLC coupled with inductively coupled plasma mass spectrometry (ICP-MS) or electrospray tandem mass spectrometry (ESI-MS-MS). At least three Te-containing metabolites were detected using HPLC-ICP-MS, and two of them were subjected to HPLC-ESI-MS-MS for identification. The MS spectra obtained by ESI-MS-MS indicated that the metabolite was Te-methyltellurocysteine oxide (MeTeCysO). Then, MeTeCysO was chemically synthesized and its chromatographic behavior matched with that of the Te-containing metabolite in garlic. The other was assigned as cysteine S-methyltellurosulfide. These results suggest that garlic can assimilate tellurate, an inorganic Te compound, and tellurate is transformed into a Te-containing amino acid, the so-called telluroamino acid. This is the first report addressing that telluroamino acid is de novo synthesized in a higher plant.
碲（Te）由于其独特的化学和物理性质而在工业中被广泛用作类金属。然而，关于 Te 在植物和动物中的生物和毒理学活性的信息有限。尽管预计 Te 将通过与硫和硒（Se）相同的途径在生物体中代谢，但在生物体中，特别是在植物中，尚不清楚确切的代谢途径。为了揭示 Te 在植物中的代谢途径，选择大蒜作为模型植物，大蒜是一种众所周知的 Se 积累植物。大蒜进行水培并暴露于碲酸钠中，使用高效液相色谱法（HPLC）与电感耦合等离子体质谱（ICP-MS）或电喷雾串联质谱（ESI-MS-MS）联用鉴定大蒜叶片水提物中的含 Te 代谢物。使用 HPLC-ICP-MS 检测到至少三种含 Te 代谢物，其中两种用 HPLC-ESI-MS-MS 进行鉴定。ESI-MS-MS 获得的 MS 谱表明该代谢物为 Te-甲基碲半胱氨酸氧化物（MeTeCysO）。然后，通过化学合成 MeTeCysO，并将其色谱行为与大蒜中含 Te 代谢物的行为相匹配。另一种被指定为半胱氨酸 S-甲基碲亚砜。这些结果表明，大蒜可以同化无机 Te 化合物碲酸盐，并且将碲酸盐转化为含 Te 的氨基酸，即所谓的碲氨基酸。这是第一个关于在高等植物中从头合成碲氨基酸的报告。
