carnitine metabolism PMID:10209289 GO:0009437 Metabolism of L-Carnitine (hydroxy-trimethyl aminobutyric acid), a derivative of the amino acid L-lysine. Its name is derived from the fact that it was first isolated from meat (carnus) in 1905. Because L-carnitine appeared to act as a vitamin in the mealworm (Tenebrio molitor), it was called vitamin BT. Vitamin BT turned out to be a misnomer when scientists discovered that humans and other higher organisms synthesize L-carnitine. Under certain conditions, the demand for L-carnitine may exceed an individual's capacity to synthesize it, making it a conditionally essential nutrient. L-Carnitine is synthesized primarily in the liver and also in the kidneys, and must be transported to other tissues. It is most concentrated in tissues that use fatty acids as their primary dietary fuel, such as skeletal and cardiac (heart) muscle. In this regard, L-carnitine plays an important role in energy production by chaperoning activated fatty acids (acyl-CoA) into the mitochondrial matrix for metabolism and chaperoning intermediate compounds out of the mitochondrial matrix to prevent their accumulation. PMID:12081978 PMID:11551212 pathway UPa:UPA00117 PMID:15731894 PMID:15518548 hydroxy-trimethyl aminobutyric acid metabolism L-Carnitine metabolism amine and polyamine metabolism