Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 22 : Fatty Acid Synthesis

Regulation of Fatty Acid Synthesis

1. Metabolism of fatty acids is under hormonal regulation by glucagons, epinephrine, and insulin.
2. Fatty acid synthesis is maximal when carbohydrate and energy are plentiful.
3. Important points of control are release of fatty acids from adipocytes and regulation of carnitine acyltransferase I in the liver.
4. High insulin levels also stimulate formation of malonyl CoA, which allosterically inhibits carnitine acyltransferase I à fatty acids remain in cytosol and are not transported to mitochondria for oxidation.
5. Key regulatory enzyme is acetyl-CoA carboxylase (catalyzes first committed step in fatty acid synthesis).
6. Insulin stimulates fatty acid synthesis and inhibits hydrolysis of stored triacylglycerols.
7. Glucagon and epinephrine inhibit fatty acid synthesis (enzyme is phosphorylated by protein kinase A; removal of phosphate group catalyzed by protein phosphatase 2A).
8. Citrate is an allosteric activator, but its biological relevance has not been established.
9. Fatty acyl CoA acts as an inhibitor.
10. Palmitoyl CoA and AMP are allosteric inhibitors.