he monocarboxylate transporters,or MCTs, are a family of proton-linked plasma membrane transporters that carry molecules having one carboxylate group (monocarboxylates), such as lactate and pyruvate, across biological membranes.Lactate has long been considered a byproduct resulting from glucose breakdown through glycolysis during anaerobic metabolism. Glycolysis requires the coenzyme NAD+, and reduces it to NADH. As a means of regenerating NAD+ to allow glycolysis to continue, lactate dehydrogenase catalyzes the conversion of pyruvate to lactate in the cytosol, oxidizing NADH to NAD+. Lactate is then transported from the peripheral tissues to the liver. There it is reformed into pyruvate and ultimately to glucose, which can travel back to the peripheral tissues, completing the Cori cycle.