Methionine is an essential amino acid which acts a precursor for transmethylation and transsulfuration. In proteins, L-methionine is the biologically active form. D-methionine is converted to L-methionine by enzymes in the body.
[2] The adenosylation of methionine results in the formation of S-adenosyl-L-methionine (SAM), which serves as a methyl donor to various substances. L-Methionine′s metabolic product glutathione is known to regulate immune response and has antiviral action.
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