L-methionine

[[File:Methionine-metabolism.jpg|thumb|Methionine metabolic pathways Key

SAM: S-adenosylmethionine (SAM-e)

SAH: S-adenosylhomocysteine

THF: tetrahydrofolate

MeCbl: methylcobalamin

1. Cystathionine beta-synthase (CBS) 2. methionine adenosyltransferase I/III 3. methionine adenosyltransferase II 4. glycine N-methyltransferase 5. numerous methyltransferases 6. S-adenosylhomocysteine hydrolase 7. methionine synthase 8. betaine-homocysteine methyltransferase 9. Serine hydroxymethyltransferase 10. methylenetetrahydrofolate reductase 11. cystathionine gamma-lyase ]] Methionine or l-methionine is the only sulfur-containing essential amino acid.

Purpose
Methionine is a pre-cursor to creatine.