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Methylselenocysteine, also known as ''Se''-methylselenocysteine, is an analog of ''S''-methylcysteine in which the sulfur atom is replaced with a selenium atom. It is an inhibitor of DMBA-induced mammary tumors〔 (【引用サイトリンク】 title=product data sheet CAS# 26046-90-2 ) 〕and a "chemopreventive agent that blocks cell cycle progression and proliferation of premalignant mammary lesions and induces apoptosis of cancer cell lines in culture."〔 (【引用サイトリンク】 title=product data sheet CAS# 26046-90-2 ) 〕 Apoptosis has been proposed as the most plausible mechanism for the chemopreventive activities of selenocompounds. ''Se''-Methylselenocysteine was more efficient at inducing apoptosis than selenite, but was less toxic." The "selenite-induced cell death could be derived from necrosis rather than apoptosis, since selenite did not significantly induce several apoptotic phenomena, including the activation of caspase-3."〔 (【引用サイトリンク】 title="Se-Methylselenocysteine induces apoptosis through caspase activation in HL-60 cells"Carcinogenesis (2001) 22 (4): 559-565. ) 〕 In the Nutritional Prevention of Cancer Trial, selenized yeast resulted in "a reduction in the incidence of prostate cancer and in total cancer incidence"; subsequent anti-cancer studies using selenomethionine did not show any benefit against cancer; but, selenized yeast contains both selenomethionine and methylselenocysteine.〔 (【引用サイトリンク】 title="Selenium Metabolism in Cancer Cells: The Combined Application of XAS and XFM Techniques to the Problem of Selenium Speciation in Biological Systems"Nutrients 2013, 5(5), 1734-1756; ) 〕 Methylselenocysteine is found in selenized yeast, and many vegetables: "As much as 80% of the total selenium" found in ''Allium''s (onion, leek, garlic, ramps) ''Brassica''s (broccoli, radish, Brussels sprouts, cabbage), and milk vetch (''Astragalus'' spp, Fabaceae) "is present as ''Se''-methylselenocysteine." The bioavailability of selenium from ''Se'' methylselenocysteine, "is likely to be similar to that from other organic selenium compounds." Specifically, "It is converted via the action of β-lyase, to methylselenol and then to hydrogen selenide, which is also the key metabolite derived from" all other common forms of selenium. But EFSA concluded that "given the absence of human studies on ''Se''-methylselenocysteine, the relatively sparse database on the bioavailability of selenium from this source and the limited data on the safety of this source compared with other selenium compounds, the Upper Limit for selenium defined by the Scientific Committee on Food cannot be used for judging its safety."〔 (【引用サイトリンク】 title="Se-methyl-L-selenocysteine added as a source of selenium for nutritional purposes to food supplements:Scientific Opinion of the Panel on Food Additives and Nutrient Sources added to Food(Question No: EFSA-Q-2005-170, EFSA-Q-2006-306, EFSA-Q-2006-308)"The EFSA Journal (2009) 1067, 1-23 ) 〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Methylselenocysteine」の詳細全文を読む スポンサード リンク
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