Fatty Acid Synthesis

Fatty Acid Synthesis

Fatty Acid Synthesis

  • Lipogenesis, the synthesis of fatty acids and their esterification to glycerol to form triacylglycerols, which occurs mainly in the liver in humans, with dietary carbohydrate as the major source of carbon.
  • While the de novo synthesis of fatty acids from acetyl-CoA occurs in the cytosol on the fatty acid synthase complex.
  • Fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases.

Fatty Acid Synthesis

Location

Fatty acid synthesis takes place in the cytosol and is carried out by a multienzyme complex called FAS (fatty acid synthase complex).

Substrates (to make one palmitate):

  • 8 acetyl CoA
  • 14 NADPH
  • 7 ATP

Products:

  • 1 molecule of palmitate (16-carbon fatty acid)
  • 7 H2O

Fatty Acid Synthesis Pathway

Fatty Acid Synthesis Pathway

  • Acetyl CoA is converted to malonyl CoA by acetyl CoA carboxylase.
  • Malonyl CoA is transferred to FAS.
  • Through a series of condensation, reduction, and dehydration reactions, the two carbons of malonyl CoA are added to the growing fatty acyl moiety on FAS.
  • FAS are then recharged with another malonyl moiety, and the cycle continues.
  • Each turn of the cycle results in the addition of a two-carbon group to the fatty acid moiety as well as the use of one ATP, one acetyl CoA, and two NADPH.
  • When the cycle has completed seven turns, the 16-carbon fatty acid (palmitate) is released from FAS.

Fatty Acids Synthesis

Important enzymes

  • Acetyl CoA carboxylase : Transforms acetyl CoA to malonyl CoA with the use of biotin and bicarbonate as cofactors. Requires one ATP.
  • Malonyl CoA transferase : Transfers the malonyl CoA molecule to FAS.
  • FAS: This collection of enzymes transfers the two carbons of malonyl CoA to the carboxyl end of the growing chain of the fatty acyl moiety. Requires two NADPH.

Activators:

  • Insulin stimulates fatty acid synthesis by dephosphorylating and, therefore, activating acetyl CoA carboxylase.

Inhibitors:

  • Glucagon and epinephrine inhibit fatty acid synthesis by inactivation of acetyl CoA carboxylase.

Significance

  • Fatty acid synthesis is a critical anabolic pathway in most organisms.
  • In addition to being the major component of membranes, fatty acids are important energy storage molecules, and fatty acyl derivatives possess a variety of physiological functions, including post-translational modification of numerous proteins.
  • Fatty acid biosynthesis is important for cell growth, differentiation, and homoeostasis. 

References

  1. David Hames and Nigel Hooper (2005). Biochemistry. Third ed. Taylor & Francis Group: New York.
  2. Smith, C. M., Marks, A. D., Lieberman, M. A., Marks, D. B., & Marks, D. B. (2005). Marks’ basic medical biochemistry: A clinical approach. Philadelphia: Lippincott Williams & Wilkins.
  3. John W. Pelley, Edward F. Goljan (2011). Biochemistry. Third edition. Philadelphia: USA.
  4. https://www.sciencedirect.com/topics/medicine-and-dentistry/fatty-acid-synthesis

Fatty Acid Synthesis

(Visited 1,004 times, 3 visits today)

Leave a Comment