Biosynthesis of Fatty Acids (De Novo)

What is the definition of the biosynthesis of palmitate FA?

Combines 8 acetyl groups from acetyl CoA to form 16-C saturated FA (palmitate)

What can occur after the biosynthesis of fatty acids?

Desaturation or elongation modification to create other FA

What is biosynthesis of fatty acids?

The broader term encompassing all processes that create FA including elongation and desaturation

De novo synthesis

• What

• Occurs in

• Substrate

• Key enzyme

• Activated by

• Inhibited by

What: Initial creation of FA from precursors like acetyl-CoA and malonyl-CoA

Occurs in: Liver and adipose tissue

Substrate: Acetyl-CoA

Key enzyme: Fatty acid synthase (FAS)

Activated by: Insulin

Inhibited by: Glucagon, epinephrine

When does de novo synthesis occurs?

When there is excess carbohydrates

What are the 4 steps in de novo synthesis?

1. Synthesis of Acetyl-CoA

2. Formation of Malonyl-CoA

3. Fatty acid chain elongation

4. Termination

Elongation & Desaturation

• What

• Occurs in

What: Processes that occur after de novo that modify initial product into various FA

Occurs in: Endoplasmic reticulum

Desaturation

• Enzyme

• Function

• Why can’t mammals create omega-3 or omega-6 (essential FA)

Enzyme: Desaturases

Function: Introduces double bonds

Mammals can’t create omega-3 or omega-6 because: Enzyme not present

What are the sources of acetyl Co-A?

• Glycolysis

• Amino acid metabolism

• Lipolysis —> FA —> beta oxidation

• Ketone bodies metabolism

What are the products of acetyl-CoA?

• Ketone bodies

• Fatty acids

• Cholesterol

• Eicosanoids

• Phospholipids

• Triglycerides

What are the 5 summary key steps of de novo synthesis?

LCRET

1. Loading: Acteyl-CoA and malonyl-CoA attach to FAS

2. Condensation: Acetyl and malonyl groups combine with CO2 release

3. Reduction, dehydration, reduction: Sequential modification of the intermediate

4. Elongation: Cycle repeats with malonyl-CoA as a 2 carbon doner

5. Termination: Release of palmitate by thioesterase