The First Step in Fatty Acid Synthesis Is Catalyzed by Acetyl-CoA Carboxylase

The First Step in Fatty Acid Synthesis Is Catalyzed by Acetyl-CoA Carboxylase 

Eight enzyme-catalyzed reactions are involved in the conversion of acetyl-CoA into fatty acids. The first reaction is catalyzed by acetyl-CoA carboxylase and requires ATP. This is the reaction that supplies the energy that drives the biosynthesis of fatty acids. The properties of acetyl-CoA carboxylase are similar to those of pyruvate carboxylase, which is important in the gluconeogenesis pathway (see chapter 12). Both enzymes contain the coenzyme biotin covalently linked to a lysine residue of the protein via its e-amino group. In the last section of this chapter we show that the activity of acetyl-CoA carboxylase plays an important role in the control of fatty acid biosynthesis in animals. Regulation of the first enzyme in a biosynthetic pathway is a strategy widely used in metabolism. 

Acetyl-CoA carboxylase of E. coli is a multienzyme complex that consists of three protein components that can be isolated individually Biotin carboxyl carrier protein (BCCP), biotin carboxylase, and carboxyltransferase (fig. 

The reaction sequence involves an initial carboxyla-tion of BCCP, catalyzed by biotin carboxylase. The C02 is covalently linked to one of the nitrogen atoms of biotin (fig. 

Subsequently, the C02 is transferred from BCCP to acetyl-CoA in a reaction catalyzed by carboxyltransferase, which yields malonyl-CoA. 

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The First Step in Fatty Acid Synthesis Is Catalyzed by Acetyl-CoA Carboxylase Seven Reactions Are Catalyzed by the Fatty Acid Synthase... 

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