As L-Carnitine Tartrate Important Cofactor for Energy Production from Fats Dietary Supplement Vegan Suitable for Vegetarians/Vegans L-Carnitine is an amino acid found in high concentrations in heart and liver tissues where, inside the cells (mitochondria), L-Carnitine helps transform fats into energy (i.e., ATP). L-Carnitine also facilitates the metabolism of carbohydrates to enhance ATP production. L-Carnitine works synergistically with Co-Q10, an antioxidant and ATP production cofactor that is found in the inner membrane of the mitochondria.