Methionine is an essential sulfur-containing amino acid that facilitates the helps initiate the translation of messenger RNA by being the first amino acid incorporated into the N-terminal position of all proteins. The terminal methyl group of the methionine side chain often participates in biochemical methyl transfer reactions making methionine a member of the “methyl donor” class of biochemicals.
• Methionine is converted into S-adenosyl methionine (SAMe), which is considered to be the activated form of methionine. This happens in the first step of the metabolism of methionine. This step requires energy in the form of ATP. In this activation of methionine, an adenosyl moiety is transferred from the ATP molecule. SAM synthesis is one of the most potent methyl donors and is involved in many methylation reactions. Its methyl group, which is attached in a sulfonium linkage with high-energy characteristics, may be donated to any of a large number of methyl-group acceptors in the presence of the appropriate enzyme.
