2.1.2. The elongation and desaturation of carbon chain of fatty acids The elongation of carbon chain of fatty acids is mainly depen- dent on the reaction of two enzyme systems including acetyl-coA carboxylic enzyme (ACCE) and fatty acid synthase (FAS) in most organisms. In the process of synthesis of fatty acids (Fig. 1), acet- yl-coA is the primer. The process of carbon chain elongation needs the cooperation with malonyl-coA, the substrate on which enzyme act are acetyl-ACP and malonyl-ACP.