Monocarboxylates such as lactate and pyruvate play a pivotal role in cellular physiology of most mammalian cells. Lactic acid, in particular, is produced in huge amounts as an end-product of glycolysis. Some tissues, such as white skeletal muscle, red blood cells and tumor cells, rely on this pathway to produce majority of their ATP under normal physiological conditions, while all tissues become dependent on this pathway during hypoxia or ischaemia. Glycolysis produces Two molecules of lactic acid are generated for every glucose molecule during glycolysis. Lactic acid must be transported out of the cell if high rates of glycolysis are to be maintained. Accumulation of lactic acid leads to a decrees in intracellular pH and cessation of glycolysis. Lactic acid transport is carried out by a recently identified family of proton-linked monocarboxylate transporters (MCTs) located at the plasma membrane. At least 9 MCTs (MCT1-9)-related genes have so far been identified in mammals, each having a different tissue distribution. MCTs also mediate the transport of many other metabolically important monocarboxylates such as pyruvate, the branched-chain oxo acids derived from leucine, valine and isoleucine, and the ketone bodies acetoacetate, -hydroxybutyrate and acetate. MCTs display a common protein topology: transmembrane -helical (TM) domains to be 12 for MCT1-3, MCT7-8 and between 10 and 12 for the other MCTs with the N- and C-termini predicted to be intracellular. Sequence homology between the isoforms is greatest for MCT1-MCT4 (> 50%), and <30% for other isoforms indicating the evolution of distinct substrate specificities and physiological role.

New Nomenclature of MCTs- Due to the identification of REMP as the new MCT3, there is a change in the nomenclature of old MCT3-MCT7. In order to avoid confusion in the listing of our MCT antibodies, we have revised our cat # to match the existing and accepted nomenclature of MCTs. The old cat # and the new Cat # are also provided to help researchers who may have used the products using the old cat#. We suggest using the NEW CAT# for ordering as the old cat # will no longer be applicable.

 

Please consult Halestrap and Price (1999) Biochem. J. 343, 281-299 for additional details.

MCT1/MOT1 is ubiquitously expressed but is especially prominent in heart and red muscle. It is upregulated in response to increased work, suggesting an important role in lactic acid oxidation. It is the major isoform in tumor cell and erythrocytes. MCT2/MOT2 is less widely distributed than MCT1. It is associated with tissues that demonstrate a high uptake affinity for lactate and pyruvate such as the kidney and liver (for gluconeogenesis) and neurons (for oxidation). MCT3/REMP is exclusively located in the basal membrane of RPE, in contrast with MCT1, which was found on the apical surface. MCT4/MOT4, most closely related to MCT3, is prominently expressed in skeletal muscle and other cells with a high glycolytic rate such as tumor cells and white blood cells, suggesting an important role in lactic acid efflux. MCT5 shares 25% sequence homology with MCT1, but it has much shorter C-terminus than other MCTs. MCT5 has an Alu insertion even in the 3'-UTR and a truncated C-terminus. High expression of MCT5 has been observed in placenta. MCT6 is highly expressed in kidney and placenta. MCT8 or XPCT (X-linked PEST Containing Transporter is highly expressed in liver, heart, and kidney.

m=mouse; r=rat; h=human; b=bovine; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CP=Cytoplasmic domain; Control peptides (unconjugated, free, antigenic peptides), because of their small size, are not recommended for Western. They should be used in ELISA/antibody blocking studies.

** Expected antibody crossreactivity information is mostly based upon high (>70%) sequence conservation of antigenic/control peptides in various species. When antibody crossreactivity has actually been experimentally confirmed in various species, it will be mentioned in the appropriate data sheets.

"Neat Antisera or antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" IgG may be more suitable for immunohistochemical (IHC) applications and to reduce background in most immunological applications including ELISA and Western.
"Control peptides" can not be used for Western as they are very short peptides. They are intended for ELISA or antibody blocking studies to establish antibody specificity.
Western blot +ve protein controls, where available, are semi-pure, pure or recombinant proteins that are formulated in SDS-PAGE sample buffer. They are recommended to be used for Western (load 10 ul/lane) for visualization with antibodies.

All Products are for in vitro research use only.