27. Biosynthesis of fatty acids. Citrate shuttle. Acyl synthase complex. Regulation of the lipogenesis. Fatty acids chain elongation and synthesis of unsaturated fatty acids.

Fatty Acid Biosynthesis

ABC Carboxylase Rxns

• Malonyl CoA formation
• Gluconeogenesis
• Odd chain fatty acid oxidation

Fatty Acid Biosynthesis

1ˢᵗ condensation rxn = 4C

6 increments x 2C = 12C

Palmitate 16C

BIOSYNTHESIS OF FATTY ACIDS

Fatty acid biosynthesis is an anabolic process building fatty acids from acetyl-CoA and malonyl-CoA precursors through a series of enzymatic reactions. It predominantly occurs in the cytosol of liver and adipose cells in humans.

Initiation:

• Begins with the carboxylation of acetyl-CoA to form malonyl-CoA.
• This reaction is catalyzed by acetyl-CoA carboxylase, a key regulatory step in fatty acid synthesis.

Elongation:

• The elongation cycle adds two carbons from malonyl-CoA to a growing fatty acid chain.
• Each cycle consists of condensation, reduction, dehydration, and a second reduction, ultimately extending the chain by two carbon atoms.
• The cycles are catalyzed by the enzyme complex fatty acid synthase.

Termination:

• The elongation process continues until the fatty acid reaches a typical length of 16 carbons (palmitate), which is then released.