Methionine (Met) is an essential amino acid and the only sub-strate for synthesis of S-adenosylmethionine (AdoMet) that is the main substrate for multiple intracellular methylases. There are two modes of Met metabolism in liver. In case of its dietary restriction Met can be metabolized via conservative remethylation cycle. In case of Met excess (high [Met]) it is mostly converted to cysteine via transsulfuration pathway.