Carnitine synthesis

Carnitine synthesis Carnitine is required for the shuttling of fatty acids into the mitochondrial matrix and its deficiency is associated with metabolic diseases. It is abundant in a typical Western diet but can also be synthesized in four steps from trimethyllysine (generated in turn by the S-adenosyl-methionine-mediated methylation of lysine residues in proteins, followed by protein hydrolysis). The enzymes that catalyze the first three steps of carnitine synthesis, converting trimethyllysine to gamma-butyrobetaine, are widely distributed in human tissues. The enzyme that catalyzes the last reaction, converting gamma-butyrobetaine to carnitine, is found only in liver and kidney cells, and at very low levels in brain tissues. Other tissues that require carnitine, such as muscle, are dependent on transport systems that mediate its export from the liver and uptake by other tissues (Bremer 1983; Kerner & Hoppel 1998; Rebouche & Engel 1980; Vaz & Wanders 2002).