Carnitine Biosynthesis

Carnitine (L-3-hydroxy-4-N,N,N-trimethylaminobutyrate) is an essential metabolite, which has a number of indispensable roles in intermediary metabolism. First, carnitine has an important role in the transport of activated long-chain fatty acids from the cytosol to the mitochondrial matrix, where β-oxidation takes place. Secondly, carnitine is involved in the transfer of the products of peroxisomal β-oxidation, including acetyl-CoA, to the mitochondria for oxidation to CO2 and H2O in the Krebs cycle. Other functions of carnitine include modulation of the acyl-CoA/CoA ratio, storage of energy as acetylcarnitine and the modulation of toxic effects of poorly metabolized acyl groups by excreting them as carnitine esters. Carnitine is present in most, if not all, animal species, and in several microorganisms and plants. Animal tissues contain relatively high amounts of carnitine, varying between 0.2 and 6 µmol.g-1, with the highest concentrations in heart and skeletal muscle. Although animals obtain carnitine primarily from the diet, most mammals are capable of synthesizing carnitine endogenously.