Complex sentence: It's an endogenous compound, synthesized from lysine and methionine, but also provided by food 95% of the levocarnitine in the body is present in heart-and skeletal muscle.
Split into simpler sentences: It's an endogenous compound, synthesized from lysine and methionine, but also provided by food. Most (95%) of the levocarnitine in the body is present in heart and skeletal muscle.