Bierla Katarzyna, Szpunar Joanna, Lobinski Ryszard, Sunde Roger A
Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Helioparc, 64053 Pau, France.
Chair of Analytical Chemistry, Faculty of Chemistry, Warsaw University of Technology, ul. Noakowskiego 3, 00-664 Warsaw, Poland.
Metallomics. 2023 Nov 2;15(11). doi: 10.1093/mtomcs/mfad067.
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.
硒代蛋氨酸（SeMet）作为蛋氨酸类似物可掺入蛋白质中。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的代谢情况，我们在缺硒饮食中给大鼠饲喂了硒含量从0至5μg Se/g不等的SeMet，持续4周，并使用高压液相色谱（HPLC）结合硒特异性电感耦合等离子体质谱（ICP-MS）和分子特异性（轨道阱MS/MS）检测法研究肝脏硒的去向和积累情况。在达到0.24μg Se/g（谷胱甘肽过氧化物酶活性达到最大值所需的硒量）时，Sec约占肝脏总硒的40%，而SeMet仅占3%-11%。对水溶性提取物的分析发现，饲喂0和0.08μg Se/g硒的大鼠中低分子量（LMW）硒物种含量可忽略不计，其中包括未检测到SeMet。在0.24μg Se/g及以上时，SeMet仅占LMW硒物种的10%，而甲基化和谷胱甘肽化硒糖占LMW硒物种的70%。在高于硒需求量时，SeMet约占蛋白质氨基酸的30%，而在饲喂5μg Se/g SeMet的大鼠中，Sec水平降至5%。最后，在一项平行研究中，与亚硒酸盐相比，高剂量SeMet与肝脏蛋白质结合的无机硒要少得多。SeMet能有效代谢并融入常见的硒代谢物库，在该库中，硒优先掺入Sec和含Sec的硒蛋白中，直至硒蛋白含量达到稳定水平；随着SeMet摄入量的增加，硒越来越多地以LMW硒糖和硒糖修饰蛋白的形式积累。
