L-Carnitine is an amino acid found in high concentrations in human heart and liver tissue, where it participates in metabolizing fatty acids into energy in the mitochondria. L-Carnitine also facilitates the metabolism of carbohydrates and enhances the rate of oxidative phosphorylation, the final stage of ATP production.

Articles:

http://en.wikipedia.org/wiki/Carnitine

http://www.umm.edu/altmed/articles/carnitine-l-000291.htm