Selenomethionine (SeMet) as a methionine analog can be incorporated into protein. In turkeys, we recently found that selenium (Se) as selenite is not metabolized to SeMet but rather to selenosugars (seleno-N-acetyl galactosamine) bound to protein as well as to selenocysteine (Sec) in selenoproteins. To characterize the metabolism of SeMet, we fed rats graded levels of SeMet from 0 to 5 µg Se/g in a Se-deficient diet for 4 wk, and investigated the fate and accumulation of liver Se using high pressure liquid chromatography (HPLC) coupled with Se-specific inductively coupled plasma mass spectrometry (ICP-MS) and molecule specific (Orbitrap MS/MS) detection. Up to 0.24 µg Se/g (Se requirement for maximal glutathione peroxidase activity), Sec accounted for ∼40% of total liver Se whereas SeMet only accounted for 3-11%. Analysis of water-soluble extracts found negligible low molecular weight (LMW) Se species in rats fed 0 and 0.08 µg Se/g, including no SeMet. At 0.24 µg Se/g and above, SeMet accounted for only 10% of LMW Se species, whereas methyl- and glutathionyl-selenosugars accounted for 70% of LMW Se species. Above the Se requirement, SeMet was ∼30% of the proteinaceous amino acids, whereas Sec levels fell to 5% in rats fed 5 µg Se/g as SeMet. Last, considerably less inorganic Se was bound to liver protein with high SeMet as compared to selenite in a parallel study. SeMet is efficiently metabolized and mixes with the common Se metabolite pool, where Se is preferentially incorporated into Sec and Sec-selenoproteins until selenoproteins plateau; with high SeMet intake, Se is increasingly accumulated as LMW selenosugars and as selenosugar-decorated proteins.

中文翻译：

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硒代蛋氨酸的补充以及大鼠肝脏中硒糖、硒代半胱氨酸和其他硒代代谢物的表达。

硒代蛋氨酸（SeMet）作为蛋氨酸类似物可以掺入蛋白质中。在火鸡中，我们最近发现亚硒酸盐形式的硒 (Se) 不会代谢为 SeMet，而是代谢为与蛋白质结合的硒糖（硒代-N-乙酰半乳糖胺）以及硒蛋白中的硒代半胱氨酸 (Sec)。为了表征 SeMet 的代谢，我们在缺硒饮食中喂食大鼠 0 至 5 µg Se/g 的 SeMet 分级水平 4 周，并使用高压液相色谱 (HPLC) 耦合研究了肝脏 Se 的命运和积累。具有 Se 特异性电感耦合等离子体质谱 (ICP-MS) 和分子特异性 (Orbitrap MS/MS) 检测。高达 0.24 µg Se/g（最大谷胱甘肽过氧化物酶活性所需的硒）时，Sec 占肝脏总硒的 40%，而 SeMet 仅占 3-11%。对水溶性提取物的分析发现，在喂食 0 和 0.08 µg Se/g（包括不含 SeMet）的大鼠中，低分子量 (LMW) Se 的含量可以忽略不计。在 0.24 µg Se/g 及以上时，SeMet 仅占 LMW Se 种类的 10%，而甲基和谷胱甘肽硒糖则占 LMW Se 种类的 70%。高于 Se 需求量时，SeMet 占蛋白质氨基酸的 30%，而在喂食 5 µg Se/g SeMet 的大鼠中，Sec 水平下降至 5%。最后，在一项平行研究中，与亚硒酸盐相比，与高 SeMet 的肝脏蛋白结合的无机硒要少得多。SeMet 被有效地代谢并与常见的 Se 代谢物池混合，其中 Se 优先掺入 Sec 和 Sec-硒蛋白中，直到硒蛋白达到稳定水平；随着 SeMet 摄入量的增加，Se 会越来越多地以 LMW 硒糖和硒糖修饰蛋白质的形式积累。