Fatty Acid Synthesis

Initiator molecule/precursor for synthesis of FAs

acetyl CoA

Fatty acids can be made from excess _______

carbohydrates

Where does fatty acid synthesis take place?

liver, adipose tissue, brain, lung, mammary gland

What part of the cell does fatty acid take place?

The cytosol

End product of fatty acid synthesis

Palmitic acid (16 C), takes 8 AceCoA

Two main enzymes in fatty acid synthesis

AceCoA carboxylase and fatty acid synthase complex

Acetyl CoA carboxylase

Carboxylates AceCoA (2c) into malonyl CoA (3c). Rate-limiting enzyme. Requires biotin

7 enzymes in fatty acid synthase complex

1. Ketoacyl synthase

2. Maolnyl/acetyl/transacylase

3. Hydratase

4. Enoyl reductase

5. Ketoacyl reductase

6. ACP (carrier)

7. Thioesterase

Stages of fatty acid synthesis

1. shuttling AceCoA from mitochondria to cytosol

2. initiation step (loading of precursors)

3. chain elongation: condensation, reduction, dehydration, reduction

Citrate shuttle

In the mitochondrial matrix, AceCoA condenses with OAA to become citrate, which crosses the membrane into the cytosol of the cell. The citrate and AceCoA separate, turning back into OAA, which turns to malate, then pyruvate.The pyruvate goes back into the mitochondrial matrix and turns back into OAA.

Further elongation after fat synthesis

After 16C palmitate is made, more Cs can be added by other systems. 2 carbons can be added at a time with elongase

Desaturation after fat synthesis

Double bonds can be created by desaturase based on the body’s need. Double bonds can only form up to carbon 9 because mammalian cells do not have D¹² or D¹⁵ desaturases