Biosynthesis of Fatty acid

Fatty acid are monocarboxylic acid (R-COOH) with hydrocarbon side chain of 4 to 36 carbon.

Some important feature of fatty acid biosynthesis

1. Fatty acid are degraded and synthesized by different pathway
2. Synthesis occur in cytoplasm in contrast with degardation, which occur in mitochrondria
3. Intermediates in fatty acid synthesis are attached to an acyl carrier proteins (ACP)
4. The enzyme catalyzes the reaction in fatty acid biosynthesis in higher organisms are joined in a single peptide chain called fatty acid synthase (FAS)
5. Fatty acid is built up by successive addition of 2 carbon units derived from acetyl CoA in each cycle.
6. After addition of 2-C unit, the intermediates are reduced by NADPH.

Citrate Shuttle (Click for large picture)

Citrate Shuttle

• FAs are synthesized in the cytoplasm from acetylCoA

• AcetylCoA generated from pyruvate by the action of PDH

and by β-oxidation of fatty acids is in the mitochondria.

• For fatty acid biosynthesis, acetylCoA has to be transported

from the mitochondria to the cytoplasm. This is done via a

shuttle system called the Citrate Shuttle.

• AcetylCoA reacts with oxaloacetate to give citrate. A

tricarboxylate translocase transports citrate from

mitochondria to cytosol.

• In the cytosol, citrate is cleaved back to oxaloacetate and

acetylCoA. This reaction is catalyzed by ATP-citrate lyase

and requires the hydrolysis of one molecule of ATP.

Citrate shuttle + fatty acid synthesis (Click for large picture)