carnitine transmembrane transport

Definition

Target type: biologicalprocess

The directed movement of carnitine across a membrane. [GO_REF:0000069, GOC:pr, GOC:TermGenie]

Carnitine transmembrane transport is a crucial process for the metabolism of fatty acids. It involves the movement of carnitine, a small organic molecule, across the mitochondrial membrane, specifically the inner mitochondrial membrane. This transport is essential for the entry of long-chain fatty acids into the mitochondria, where they can be broken down for energy production via beta-oxidation. The process is facilitated by a family of transmembrane proteins known as carnitine acyltransferases (CATs). There are three major CATs: CAT1, CAT2, and CPT1.

CAT1 is primarily responsible for the uptake of carnitine into the cytoplasm from the blood. CAT2 is located on the inner mitochondrial membrane and facilitates the transfer of carnitine from the cytoplasm into the mitochondrial matrix. CPT1, also located on the inner mitochondrial membrane, is responsible for the formation of acylcarnitine, a derivative of carnitine that is able to cross the mitochondrial membrane.

The carnitine shuttle begins when a long-chain fatty acid is activated by attaching to CoA to form acyl-CoA. Acyl-CoA cannot directly cross the mitochondrial membrane. Therefore, CPT1 catalyzes the transfer of the acyl group from CoA to carnitine, forming acylcarnitine. Acylcarnitine can then cross the mitochondrial membrane via the carnitine/acylcarnitine translocase (CACT), which is a transporter protein that exchanges acylcarnitine for carnitine.

Once inside the mitochondrial matrix, CAT2 transfers the acyl group back to CoA, regenerating acyl-CoA. This acyl-CoA can now enter the beta-oxidation pathway, where it is broken down into acetyl-CoA, which can be used for energy production. Carnitine is then transported back out of the mitochondrial matrix by CACT, completing the carnitine shuttle.

The carnitine shuttle plays a critical role in energy metabolism. It allows the body to use long-chain fatty acids as a source of energy, particularly during periods of fasting or exercise when glucose levels are low. Disorders affecting the carnitine shuttle can lead to various metabolic problems, such as muscle weakness, hypoglycemia, and cardiomyopathy.'
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Proteins (4)

Compounds (6)