carnitine transport

Definition

Target type: biologicalprocess

The directed movement of carnitine into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. Carnitine is a compound that participates in the transfer of acyl groups across the inner mitochondrial membrane. [GOC:ai]

Carnitine transport is a vital process in the metabolism of fatty acids, particularly in the energy production of cells. It facilitates the movement of long-chain fatty acids from the cytoplasm into the mitochondria, where they are broken down through beta-oxidation to generate ATP.

The process begins with the conversion of long-chain fatty acids to acyl-CoA in the cytoplasm. However, acyl-CoA cannot directly cross the mitochondrial membrane. Carnitine, a small organic molecule, plays a crucial role in this transport.

1. **Carnitine Palmitoyltransferase I (CPT1):** Located on the outer mitochondrial membrane, CPT1 catalyzes the transfer of the acyl group from acyl-CoA to carnitine, forming acyl-carnitine. This reaction is rate-limiting and is regulated by various factors, including insulin, glucagon, and the availability of free carnitine.

2. **Carnitine-Acylcarnitine Translocase (CACT):** This transmembrane protein facilitates the exchange of acyl-carnitine from the cytosol into the mitochondrial matrix and carnitine from the matrix to the cytosol.

3. **Carnitine Palmitoyltransferase II (CPT2):** Located on the inner mitochondrial membrane, CPT2 catalyzes the transfer of the acyl group from acyl-carnitine back to CoA, regenerating acyl-CoA inside the mitochondria. This reaction is irreversible.

Once inside the mitochondria, acyl-CoA undergoes beta-oxidation, a series of reactions that break down fatty acids into acetyl-CoA, generating ATP.

Carnitine transport is essential for energy production, particularly during periods of fasting or exercise when fatty acids are the primary energy source. Deficiencies in carnitine or defects in carnitine transport proteins can lead to various metabolic disorders, including muscle weakness, fatigue, and hypoglycemia.

In addition to its role in fatty acid metabolism, carnitine has other important physiological functions. It is involved in the removal of toxic compounds, such as ammonia, and acts as an antioxidant. It is also essential for normal brain and nerve function.'
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Proteins (4)

Compounds (6)