www.carnitinaofficialsite.it Biosynthesis In nature, carnitine is present in all the cells of the body where it carries out essential functions. The greatest concentration of carnitine is found in skeletal and cardiac muscle tissues. 75% of the carnitine contained in the human body is diet derived (from meat, fish and dairy products) and 25% is synthesised in the body, mainly in the liver and the kidneys, and to a lesser extent in the brain, starting from two amino acids, lysine and methionine. These two amino acids are converted to gamma-butyrobetaine which, in the presence of gamma-butyrobetaine hydroxylase, is converted to carnitine. Although the heart and skeletal muscles are the tissues richest in carnitine, they cannot synthesise it as they do not have gamma-butyrobetaine hydroxylase, which catalyses the last phase of the biosynthetic process. Transport Carnitine passes from the blood to other body tissues through a process of active cell transport. As of today, two carnitine transporters have been identified, positioned on cell membranes: the OCTN transporters ( OCTN1 and OCTN2) and the ATB transporters.