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CAS number 4727-40-6 YesY
PubChem 145692
ChemSpider 128519
KEGG C03172
Jmol-3D images Image 1
Molecular formula C6H15NO2S+
Molar mass 164.247 g/mol
Melting point 139 °C (282 °F)[1] (bromide salt, decomp.)
134 °C (273 °F)[1] (chloride salt, decomp.)
LD50 2760 mg/kg (iv, mice, chloride salt)[1]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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.[2]

Vitamin U is a synonym for S-methylmethionine.[3] The term was coined in 1950 by Garnett Cheney for anti-ulcerogenic[4] factors in raw cabbage juice that speed healing of peptic ulcers. It is claimed to have protective effects in the gastrointestinal mucosa and in the liver.[5]

Biosynthesis and biochemical function[edit]

S-Methylmethionine arises via the methylation of methionine by S-adenosyl methionine (SAM). The coproduct is S-adenosyl homocysteine.[2]

The biological roles of S-methylmethionine are not well understood. Speculated roles include methionine storage, use as a methyl donor, regulation of SAM.[2] A few plants use S-methylmethionine as a precursor to the osmolyte dimethylsulfoniopropionate (DMSP). Intermediates include dimethylsulfoniumpropylamine and dimethylsulfoniumpropionaldehyde.[6]

Beer flavor precursor in barley malt[edit]

S-Methylmethionine is found in barley and during the malting process, particularly the curing stage in kilning, heat causes it to break down to form dimethyl sulfide (DMS).[7]


  1. ^ a b c d Merck Index, 12th ed., 10165 ISBN 0-911910-12-3
  2. ^ a b c Bourgis F (1999). "S-methylmethionine plays a major role in phloem sulfur transport and is synthesized by a novel type of methyltransferase". The Plant Cell Online 11 (8): 1485–1498. doi:10.1105/tpc.11.8.1485. 
  3. ^ National Center for Biomedical Ontology. "Methylmethionine Sulfonium Chloride". 
  4. ^ Cheney G (September 1950). "Anti-peptic ulcer dietary factor (vitamin "U") in the treatment of peptic ulcer". J Am Diet Assoc 26 (9): 668–72. PMID 15436263. 
  5. ^ Patel AD, Prajapati NK (2012). "Review on Biochemical Importance of Vitamin-U". Journal of Chemical and Pharmaceutical Research 4 (1): 209–215. 
  6. ^ McNeil SD (1999). "Betaines and related osmoprotectants. Targets for metabolic engineering of stress resistance". Plant Physiology 120 (4): 945–949. doi:10.1104/pp.120.4.945. 
  7. ^ Hornsey IS (1999). Brewing. Royal Society of Chemistry. p. 47. ISBN 9780854045686. 

External links[edit]