Fatty acid synthesis

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Fatty acids are formed by the action of Fatty acid synthases from acetyl-CoA and malonyl-CoA precursors. In humans fatty acids are predominantly formed in the liver and adipose tissue, and mammary glands during lactation. Most of acetyl-CoA is formed in the mitochondria and is transported into cytosol in the form of citrate.

Contents 1 Elongation 1.1 Condensation 1.2 Reduction of acetoacetyl ACP 1.3 Dehydration 1.4 Reduction of crotonyl ACP

[edit] Elongation

Much like β-oxidation, elongation occurs via four recurring reactions:

1. Condensation
2. Reduction
3. Dehydration
4. Reduction

In the second step of elongation, butyryl ACP condenses with malonyl ACP to form an acyl ACP compound. This continues until a C₁₆ acyl compound is formed, at which point it is hydrolyzed by a thioesterase into palmitate and ACP.

[edit] Condensation

The first step is condensation of acetyl ACP and malonyl ACP, catalyzed by acyl-malonyl ACP condensing enzyme. This results in the formation of acetoacetyl ACP.

Although this reaction is thermodynamically unfavourable, the evolution of CO₂ drives the reaction forward.

[edit] Reduction of acetoacetyl ACP

In this step, acetoacetyl ACP is reduced by NADPH into D-3-Hydroxybutyryl ACP. This reaction is catalyzed by β-Ketoacyl ACP reductase. The double bond is reduced to a hydroxyl group. Only the D isomer is formed.

[edit] Dehydration

In this reaction, D-3-Hydroxybutyryl ACP is dehydrated to crotonyl ACP. This reaction is catalyzed by 3-Hydroxyacyl ACP dehydrase.

[edit] Reduction of crotonyl ACP

During this final step, crotonyl ACP is reduced by NADPH into butyryl ACP. This reaction is catalyzed by enoyl ACP reductase.

v • d • e Lipid metabolism: lipid metabolism
Fatty acid degradation (Lipolysis, Beta oxidation) - Fatty acid synthesis