β-Oxidation of Fatty Acids. Fatty acids are bound to albumin before being transported around the body, and are taken up into by the myocardium in the unbound form, which is mediated by transport proteins in the sarcolemma [38-39]. Inside the cardiomyocyte, fatty acids are activated by the addition of acyl-CoA by the action of acyl-CoA synthetase. To aid its entry in the mitochondria this acyl group is first passed from acyl-CoA to carnitine by carnitine-acyl transferase I, to form acyl-carnitine. Fatty acid transport across the inner mitochondrial membrane is facilitated by the exchange of acyl-carnitine for carnitine, by carnitine- acyl-carnitine translocase. Once inside the matrix, carnitine is cleaved off of the fatty acid chain and replaced again with CoA, by carnitine-acyl transferase II. The acyl-CoA molecule is then metabolised in a sequence of four reactions; oxidation, hydration, further oxidation, and a final thiolysis reaction. These reactions continue until the acyl molecule is fully degraded. Each cycle of reactions yield a molecule of acyl-CoA that has been shorted by two carbon atoms and a molecule of acetyl-CoA (figure 1.2), that passes on to the tricarboxylic acid cycle (TCA). The first oxidation reaction also generates one molecule each of FADH2 and NADH, both of which pass directly on to the electron transport chain [36-37], described later in section 1.4.5.
