L-carnitine in pathways of energy metabolism
The homeostasis of cellular energy metabolism relies on the availability of two major
sources of substrates: FA and carbohydrates. Through catabolic processes, both substrates
provide a metabolite, acetyl coenzyme A (acetyl-CoA), which further undergoes oxidation
in the mitochondrial machinery to provide cellular metabolism with adenosine-5'-
triphosphate (ATP) molecules, the "molecular unit of currency" of intracellular energy
transfer (Koves et al., 2008a). The role of L-carnitine in regulating cellular energy
metabolism is schematically summarised in Fig. 1. First, L-carnitine is a substrate of the
enzyme L-carnitine palmitoyltransferase-1 (CPT I), which catalyses the rate-limiting reaction
in the transfer of FA into the mitochondria (Kuhajda et al., 2007). The key mechanism for
regulation of CPT I activity is allosteric inhibition by malonyl CoA