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|Section2= |Section3= }} ''S''-Methylmethionine (SMM) is a derivative of methionine with the chemical formula (CH3)2S+CH2CH2CH(NH3+)CO2−. This cation is an intermediate in many biosynthetic pathways owing to the sulfonium functional group. The natural derivative ''S''-methylmethionine is biosynthesized from L-methionine which is first converted to ''S''-adenosylmethionine. The subsequent conversion, involving replacement of the adenosyl group by a methyl group is catalyzed by the enzyme methionine S-methyltransferase. ''S''-methylmethionine is particularly abundant in plants, being more abundant than methionine. ''S''-Methylmethionine is sometimes referred to as ''vitamin U'',〔(【引用サイトリンク】title=Methylmethionine Sulfonium Chloride )〕 but it is not considered a true vitamin. The term was coined in 1950 by Garnett Cheney for uncharacterized anti-ulcerogenic factors in raw cabbage juice that may help speed healing of peptic ulcers. ''S''-Methylmethionine is claimed to have protective effects in the gastrointestinal mucosa and in the liver. ==Biosynthesis and biochemical function== ''S''-Methylmethionine arises via the methylation of methionine by ''S''-adenosyl methionine (SAM). The coproduct is ''S''-adenosyl homocysteine.〔 The biological roles of ''S''-methylmethionine are not well understood. Speculated roles include methionine storage, use as a methyl donor, regulation of SAM.〔 A few plants use ''S''-methylmethionine as a precursor to the osmolyte dimethylsulfoniopropionate (DMSP). Intermediates include dimethylsulfoniumpropylamine and dimethylsulfoniumpropionaldehyde. 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「S-Methylmethionine」の詳細全文を読む スポンサード リンク
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