What Are the Important Enzymes in Fatty Acid Breakdown and Creation?

Fatty acid metabolism is all about two main processes:

1. Oxidation – This is when fatty acids are broken down to produce energy.
2. Synthesis – This is when fatty acids are made for storage and other purposes.

A group of important enzymes helps control these processes. Let’s take a closer look at the enzymes involved in both breaking down and creating fatty acids and how they help our bodies.

Fatty Acid Breakdown

Fatty acid oxidation mainly happens in a part of the cell called the mitochondria. This is where fats are broken down to make energy. The following enzymes are key to this process:

1. Acyl-CoA Synthetase:

   • This enzyme "activates" fatty acids, turning them into a form called acyl-CoA.
   • To do this, it needs a special energy molecule called ATP.
   • For example, it changes palmitic acid into palmitoyl-CoA, which can then enter the mitochondria.

2. Carnitine Acyltransferase I (CAT I):

   • Located on the outside of the mitochondria, this enzyme helps move acyl groups from CoA to carnitine, creating a new form called acylcarnitine.
   • This is important because acyl-CoA cannot get through the mitochondrial wall on its own.

3. Carnitine Acyltransferase II (CAT II):

   • Inside the mitochondria, this enzyme turns acylcarnitine back into acyl-CoA once it has crossed into the mitochondria.

4. Fatty Acid Dehydrogenases:

   • This group of enzymes starts the breaking down process called β-oxidation. They help add a double bond to acyl-CoA.
   • There are different types of these enzymes for short, medium, and long fatty acid chains.

5. Enoyl-CoA Hydratase:

   • This enzyme helps to add water to the double bond, forming a hydroxyl group.

6. 3-Hydroxyacyl-CoA Dehydrogenase:

   • This enzyme changes the hydroxyl group into a keto group, producing 3-ketoacyl-CoA.

7. Thiolase:

   • This enzyme finishes the β-oxidation process by breaking down 3-ketoacyl-CoA into acyl-CoA and acetyl-CoA. Acetyl-CoA can then enter another energy-producing cycle called the TCA cycle.

Fatty Acid Creation

On the other hand, fatty acid synthesis, also known as lipogenesis, mainly occurs in the cytoplasm of cells. This process uses acetyl-CoA and another molecule called NADPH to build long chains of fatty acids. The main enzymes involved are:

1. Acetyl-CoA Carboxylase (ACC):

   • This enzyme changes acetyl-CoA into malonyl-CoA, which is a crucial step in making fatty acids. It needs ATP and another molecule called biotin to work.

2. Fatty Acid Synthase (FAS):

   • This complex of enzymes works together to add two-carbon units from malonyl-CoA to grow the fatty acid chain. This involves several steps, including joining, reducing, drying out, and reducing again.

3. Thioesterase:

   • This enzyme works at the end of the synthesis process. It releases the newly created fatty acid from the fatty acid synthase complex.

Summary

Learning about the enzymes that break down and create fatty acids helps us understand how our bodies manage energy and fats. These enzymes play important roles, whether we need energy from stored fats during fasting or need to make fats for energy storage after eating. By keeping a balance between these processes, our bodies make sure we have enough fuel for immediate energy needs and for later storage.