L Carnitine 500 mg Carnitine Protocol for Life Balance L carnitine is primarily synthesized in the liver from the amino acids lysine and methionine through a series of four enzymatic reactions, with the liver and kidneys converting the precursor butyrobetaine into active L Carnitine Linus Pauling Institute Oregon State University JCI l Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans