Metabolism of saturated fatty acids

The free fatty acid needs activating before it can be metabolized. This is achieved by conversion into 

The fatty acid is initially converted into an acyl-AMP derivative by attack of the carboxylate as a nucleophile onto the P=0 system of ATP, with loss of diphosphate as a leaving group. This reaction is far from favourable, and the equilibrium is disturbed by subsequent pyrophosphatase-catalysed hydrolysis of diphosphate into two molecules of phosphate. 

This means that the energy demands (ATP AMP) are equivalent to two ATP ADP transformations. However, the product fatty acyl-AMP is actually a reactive mixed anhydride and may be attacked 

Oxidation at the (i-position is then achieved by the same sequence of dehydrogenation, hydration, and dehydrogenation reactions that we have seen 

Because of the enzyme specificity in the hydration step, the new carbonyl group is introduced 3 to the original thioester carbonyl. The sequence includes two dehydrogenation reactions, and involves both FAD and NAD+ as coenzymes. The reduced forms of these coenzymes can be reoxidized by means of 

---