BIC 101 :: Lecture 27 :: FATTY ACID AND TRIACYL GLYCEROL BIOSYNTHESIS

Biosynthesis of fatty acids

• It was thought that fatty acid biosynthesis occurred by reversal of the oxidation pathway. 
• On the contrary, it occurs by a separate pathway that differs from -oxidation in several ways.

i. Synthesis takes place in the cytosol, in contrast with degradation or oxidation, which occurs in the mitochondrial matrix.
ii. Intermediates in fatty acid synthesis are covalently linked to the sulfhydryl group of an acyl carrier protein (ACP) whereas intermediates in fatty acid breakdown are bonded to coenzyme A.
iii. The enzymes of fatty acid synthesis in animals are joined in a single polypeptide chain called fatty acid synthase.  In contrast, the degradative enzymes do not seem to be  associated.  Plants employ separate enzymes to carry out the biosynthetic reactions.
iv. The reductant in fatty acid synthesis is NADPH,  whereas the oxidants in fatty acid oxidation are NAD+ and FAD.
Pathway for the movement of acetyl-CoA units from within the mitochondrion to the cytoplasm for use in lipid and cholesterol biosynthesis.

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