Carnitine Palmitoyltransferase II Deficiency - Overview

Overview

Carnitine is a hydrophilic natural substance acquired mostly through dietary meats and dairy products and is used by cells to transport hydrophobic fatty acids. The "carnitine shuttle" is composed of three enzymes that utilize carnitine to facilitate the import of hydrophobic long-chain fatty acids from the cytosol into the mitochondrial matrix for the production of energy via β-oxidation.

• Carnitine palmitoyltransferase I (CPT I) is localized to the outer mitochondrial membrane and catalyzes the esterification reaction between carnitine and palmitoyl-CoA to produce palmitoylcarnitine. Three tissue-specific isoforms (liver, muscle, brain) have been identified.
• Carnitine-acylcarnitine translocase (CACT) is an integral inner mitochondrial membrane protein that transports palmitoylcarnitine from the intermembrane space into the matrix in exchange for a molecule of free carnitine that is subsequently moved back out of the mitochondria into the cytosol.
• Carnitine palmitoyltransferase II (CPT II) is a peripheral inner mitochondrial membrane protein ubiquitously found as a monomeric protein in all tissues that oxidize fatty acids. It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is now an activated substrate for β-oxidation inside the matrix.