Difference Between Acetyl CoA and Acyl CoA

The key difference between acetyl CoA and acyl CoA is that acetyl CoA (or acetyl Coenzyme A) helps in protein, carbohydrate, and lipid metabolism whereas acyl CoA (or acyl Coenzyme A) helps in the metabolism of fatty acids.

Acetyl CoA is very useful in delivering the acetyl group to the Krebs cycle for energy production. An acetyl group is a functional group having the chemical formula -C(O)CH₃. An acyl group is also a functional group having the chemical formula –C(O)R where the R group is a fatty acid side chain. It is useful in the production of energy via converting into acetyl CoA.

CONTENTS

1. Overview and Key Difference
2. What is Acetyl CoA 
3. What is Acyl CoA
4. Side by Side Comparison – Acetyl CoA vs Acyl CoA in Tabular Form
5. Summary

What is Acetyl CoA?

Acetyl CoA or acetyl Coenzyme A is an important molecule involved in the metabolism of proteins, carbohydrates, and lipids. It is useful in delivering the acetyl functional group to the Krebs cycle for the production of energy. There, the acetyl CoA oxidizes, producing ATP.

Acetyl CoA forms from the combination of several amino acids, pyruvate, and fatty acids. Acetylating the CoA gives acetyl CoA, and this occurs via the glycolysis of carbohydrates and beta-oxidation of fatty acids. This molecule has a thioester linkage which is highly reactive due to its high energy content. Therefore, the hydrolysis of this thioester bond is exergonic (which means, it releases energy to the surrounding).

After acetyl CoA enters the Krebs cycle, it oxidizes to carbon dioxide (CO₂) and water (H₂O). And this oxidation releases energy, which is then captured as ATP and GTP molecules. One acetyl CoA helps to produce 11 ATP and one GTP.

What is Acyl CoA?

Acyl CoA is an important molecule used in fatty acid metabolism. It is a group of coenzymes. This compound has a coenzyme A attached to a fatty acid chain. It is a temporary compound which easily breakdowns into Coenzyme and fatty acid.

Acyl CoA compound is very important in energy production of animals because it converts into acetyl CoA and, enters the Krebs cycle to produce ATP and GTP. The beta-oxidation of acyl CoA produces acetyl CoA.

When forming the acyl CoA molecule, a fatty acid undergoes a two-step reaction for the activation of the fatty acid. The Acyl-CoA synthetase catalyzes this reaction. In the first step, the fatty acid displaces the diphosphate group of an ATP molecule (An ATP molecule is a triphosphate molecule) and thus, produces AMP (adenosine monophosphate). In the second step, a coenzyme A displaces the AMP part of the molecule to form acyl CoA.

What is the Difference Between Acetyl CoA and Acyl CoA?

Acetyl CoA vs Acyl CoA
Acetyl CoA is an important molecule involved in the metabolism of proteins, carbohydrates, and lipids.	Acyl CoA is an important molecule used in fatty acid metabolism.
Role in Metabolism
Helps in the metabolism of proteins, carbohydrates, and lipids.	Helps in the metabolism of fatty acids.
Reaction Mechanism
Enters the Krebs cycle to produce ATP and GTP.	Converts into acetyl CoA, which in turn, enters the Krebs Cycle to produce ATP and GTP.
Formation
Forms by a combination of several amino acids, pyruvate, and fatty acids.	Forms by a two-step reaction involving a fatty acid (for the activation of the fatty acid).

Summary – Acetyl CoA vs Acyl CoA

Acetyl CoA and acyl CoA are forms of coenzymes. These are very important molecules in the metabolism of different biological compounds. The key difference between acetyl CoA and acyl CoA is that the acetyl CoA helps in protein, carbohydrate, and lipid metabolism whereas, the acyl CoA helps in the metabolism of fatty acids.

Reference:

1. “Acetyl-CoA.” Wikipedia, Wikimedia Foundation, 22 Apr. 2018, Available here.
2. “Acyl-CoA.” Wikipedia, Wikimedia Foundation, 22 Apr. 2018, Available here.
3. “Acetyl Coenzyme A.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Acetyl-CoA” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Acyl-CoA2” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia