Monocarboxylate Transporter

Monocarboxylates such as pyruvate, lactate, and the ketone bodies (acetoacetate and b-hydroxybutyrate) play essential roles in carbohydrate, fat, and amino acid metabolism and must be rapidly transported across the plasma membrane of cells. Transport is mediated by proton-linked monocarboxylate transporters (MCTs), four of which (MCTs1–4) have been characterized in detail. They are part of a family of transporter proteins, known as the MCT or SLC16 solute carrier family, that share characteristic sequence motifs. All family members are predicted to have 12-transmembrane helices (TMs) with intracellular C- and N-termini and a large cytosolic loop between TMs 6 and 7. As in other major facilitator superfamily members, the TM regions are more conserved than the loops and C-terminus. The MCT family has a total of 14 members whose predicted phylogeny, only MCTs1–4 have been confirmed to function as proton-linked MCTs. MCT10 was identified as an aromatic amino acid transporter originally called T-type amino acid transporter 1 (TAT1) and MCT8 shown to be an important thyroid hormone transporter. Transport mediated by MCT8 and MCT10 is not proton linked. The function of the other eight MCTs is unknown. In addition to their normal metabolic roles, MCTs may also be important for the transport of some drugs across the plasma membrane. There are also two distinct sodium-linked monocarboxylate transporters that are members of the SLC5 solute carrier family. These play a key role in endothelial monocarboxylate transport in the gut and kidney.


1.Halestrap AP. IUBMB Life. 2012;64(1):1–9.