L-Carnitine is a quaternary ammonium compound synthesized from the amino acids lysine and methionine. While not a standard α-amino acid, it plays a crucial role in fatty acid metabolism by transporting long-chain fatty acids into the mitochondria for energy production. Carnitine is important for energy metabolism, particularly during exercise, and helps support heart and muscle function. It also plays a role in the removal of toxic compounds from the mitochondria.