Carnitine acetyltransferase in pea cotyledon mitochondria

Area of Science:

• Mitochondrial Physiology
• Plant Biochemistry

Background:

• Mitochondria are key organelles for cellular respiration.
• Acetyl-CoA is a crucial metabolic intermediate, but its transport across the mitochondrial membrane is regulated.

Purpose of the Study:

• To investigate the transport of acetyl-CoA and acetylcarnitine across the mitochondrial membrane in pea cotyledons.
• To elucidate the role of carnitine acetyltransferase in this process.

Main Methods:

• Purification of pea cotyledon mitochondria.
• Oxidation assays using acetyl-CoA and acetylcarnitine.
• Radioactive assays to detect carnitine acetyltransferase activity.
• Experiments with intact and disrupted mitochondria/mitoplasts.

Main Results:

• Purified pea mitochondria oxidized acetylcarnitine but not acetyl-CoA in the presence of carnitine.
• Carnitine acetyltransferase activity was detected in intact mitochondria only with a sensitive radioactive assay.
• Disrupting mitochondria allowed acetyl-CoA to be utilized by matrix carnitine acetyltransferase.
• Acetylcarnitine transport across the inner mitochondrial membrane is proposed via a carnitine:acylcarnitine translocator.

Conclusions:

• The inner mitochondrial membrane acts as a barrier to acetyl-CoA.
• Acetylcarnitine is transported across this barrier by a specific translocator.
• This transport mechanism may facilitate the movement of acetylcarnitine from the mitochondrial matrix to extra-mitochondrial sites in pea cotyledons.