L-Carnitine

L-Carnitine (beta-hydroxy-gamma-butyrobetaine) functions as an obligate transporter for long-chain fatty acids across the inner mitochondrial membrane. It combines with acyl-CoA esters at the outer mitochondrial membrane to form acylcarnitines, which are transported into the mitochondrial matrix by the carnitine-acylcarnitine translocase system. Inside the matrix, the fatty acid is released for beta-oxidation and ATP production. Without adequate carnitine, long-chain fatty acids accumulate in the cytosol and cannot enter the oxidative phosphorylation pathway.