Conformations of carnitine and acetylcarnitine and the relationship to mitochondrial transport of fatty acids

The conformations of carnitine and acetylcarnitine by EHT and CNDO/2 molecular orbital calculations show that carnitine has two low energy conformers. One of these is an extended conformer corresponding to a charge separated species, while the other is a folded conformer having a charged onium head and carboxylate anion in close proximity forming an internal ionic bond. These results suggest that the folded conformation is responsible for the active transport of acetyl- and acyl-carnitine by enzymes which transfer acyl groups into the mitochondria for subsequent fatty acid oxidation.