ABSTRACT
Fatty acid breakdown brings about the oxidation of long-chain fatty acids. The fatty acids are first converted to their acyl coenzyme A (CoA) derivatives and then degraded by the successive removal of two-carbon units from the end of the fatty acid as acetyl CoA. Fatty acid breakdown occurs in the cytosol of prokaryotes and in the mitochondrial matrix of eukaryotes. Before entering the mitochondrial matrix, the fatty acid is activated by forming a thioester link with CoA. Small- and medium-chain acyl CoA molecules are readily able to cross the inner mitochondrial membrane by diffusion. The breakdown of individual fatty acids occurs as a repeating sequence of four reactions: oxidation, hydration, oxidation and thiolysis. Unsaturated fatty acids require some additional processing before they can be unsaturated degraded completely by β-oxidation. The major source of free fatty acids in the blood is from the breakdown of triacylglycerol stores in adipose tissue which is regulated by the action of hormone-sensitive triacylglycerol lipase.
