Methionine
Methionine is a sulfur-containing, essential proteinogenic amino acid (C5H11NO2S) that humans and other animals must obtain from the diet. The L-form is incorporated into proteins and is encoded by the AUG start codon. It is supplied in pharmacopoeial, food, feed and reagent grades for cell culture media, parenteral nutrition, animal feed and as an antioxidant excipient in biopharmaceutical formulations.
Available from Molekula
L-Methionine
We manufacture and supply L-Methionine. See specifications, pack sizes and pricing, or ask us for a quote.
Methionine (Met, M) is an α-amino acid with a thioether side chain. L-methionine (CAS 63-68-3) is the biologically relevant enantiomer. The racemate DL-methionine (CAS 59-51-8) is widely produced for animal feed. Its molar mass is approximately 149.21 g/mol.
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What role does methionine play in biology?
Methionine is an essential amino acid. In most organisms it is the first residue incorporated during protein synthesis, because the start codon AUG encodes it. In bacteria, initiation uses N-formylmethionine. Methionine is the precursor of S-adenosylmethionine (SAM), the principal biological methyl donor. Through homocysteine and the transsulfuration pathway, it also supplies the sulfur for cysteine.
Where is methionine used in industry and the laboratory?
- Cell culture media and parenteral nutrition: L-methionine is a standard component.
- Animal feed: DL-methionine and related analogues are used as feed additives, particularly for poultry.
- Biopharmaceutical formulations: methionine is added as an excipient to scavenge oxidants and protect susceptible residues in therapeutic proteins.
- Structural biology: selenomethionine-labelled proteins are used for phasing in X-ray crystallography.
Which grades and quality parameters should buyers check?
Monographs for methionine exist in the USP and the European Pharmacopoeia (EP). Food and feed grades are also available, alongside general reagent grades. When procuring methionine, specify the following:
- the enantiomeric form (L, D or DL)
- assay
- specific optical rotation
- related substances
- heavy metals or elemental impurities
- loss on drying
- endotoxin limits for cell culture or parenteral use
Always request the CoA and SDS. Because the thioether readily oxidises to methionine sulfoxide, storage conditions and oxidation-related impurities are relevant quality considerations.
Related concepts
Cysteine, homocysteine, S-adenosylmethionine (SAM), N-formylmethionine, methionine sulfoxide, selenomethionine, essential amino acids, transsulfuration pathway, cell culture media.
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